Xin Chen

This review presents the past and current efforts with a brief description on the featured properties of hydrogel membranes fabricated from biopolymers and synthetic ones for wound dressing applications. Many endeavors have been exerted during past ten years for developing new artificial polymeric membranes, which fulfill the demanded conditions for the treatment of skin wounds. This review mainly focuses on representing specifications of ideal polymeric wound dressing membranes, such as crosslinked hydrogels compatible with wound dressing purposes. But as the hydrogels with single component have low mechanical strength, recent trends have offered composite or hybrid hydrogel membranes to achieve the typical wound dressing requirements.

A series of excellent poly(vinyl alcohol) (PVA)/polymers blend hydrogel were reviewed using different crosslinking types to obtain proper polymeric dressing materials, which have satisfied biocompatibility and sufficient mechanical properties. The importance of biodegradable–biocompatible synthetic polymers such as PVA, natural polymers such as alginate, starch, and chitosan or their derivatives has grown significantly over the last two decades due to their renewable and desirable biological properties. The properties of these polymers for pharmaceutical and biomedical application needs have attracted much attention. Thus, a considered proportion of the population need those polymeric medical applications for drug delivery, wound dressing, artificial cartilage materials, and other medical purposes, where the pressure on alternative polymeric devices in all countries became substantial. The review explores different polymers which have been blended previously in the literature with PVA as wound dressing blended with other polymeric materials, showing the feasibility, property change, and purpose which are behind the blending process with PVA.

Biochar has emerged as an efficient tool to affect bioavailability of heavy metals in contaminated soils. Although partially understood, a carefully designed incubation experiment was performed to examine the effect of biochar on mobility and redistribution of Cd, Cu, Pb and Zn in a sandy loam soil collected from the surroundings of a copper smelter. Bamboo and rice straw biochars with different mesh sizes (<0.25 mm and <1 mm), were applied at three rates (0, 1, and 5% w/w). Heavy metal concentrations in pore water were determined after extraction with 0.01 M CaCl2. Phytoavailable metals were extracted using DTPA/TEA (pH 7.3). The European Union Bureau of Reference (EUBCR) sequential extraction procedure was adopted to determine metal partitioning and redistribution of heavy metals. Results showed that CaCl2-and DTPA-extractable Cd, Cu, Pb and Zn concentrations were significantly (p < 0.05) lower in the bamboo and rice straw biochar treated soils, especially at 5% application rate, than those in the unamended soil. Soil pH values were significantly correlated with CaCl2-extractable metal concentrations (p < 0.01). The EUBCR sequential extraction procedure revealed that the acid extractable fractions of Cd, Cu, Pb and Zn decreased significantly (p < 0.05) with biochar addition. Rice straw biochar was more effective than bamboo biochar in decreasing the acid extractable metal fractions, and the effect was more pronounced with increasing biochar application rate. The effect of biochar particle size on extractable metal concentrations was not consistent. The 5% rice straw biochar treatment reduced the DTPA-extractable metal concentrations in the order of Cd < Cu < Pb < Zn, and reduced the acid extractable pool of Cd, Cu, Pb and Zn by 11, 17, 34 and 6%, respectively, compared to the control. In the same 5% rice straw biochar treatments, the organic bound fraction increased by 37, 58, 68 and 18% for Cd, Cu, Pb and Zn, respectively, compared to the control, indicating that the immobilized metals were mainly bound in the soil organic matter fraction. The results demonstrated that the rice straw biochar can effectively immobilize heavy metals, thereby reducing their mobility and bioavailability in contaminated soils.

2D MXenes have attracted extensive attentions owing to their anisotropy, high conductivity and other extraordinary properties. The popular preparation method of MXenes usually involves HF in high concentrations, which has seriously restricted their pervasive applications. In this work, a new hydrothermal route with low-toxicity etching agents (NaBF4, HCl) was used to synthesize Ti3C2 MXene (h-Ti3C2). Compared with the Ti3C2 prepared by the traditional HF etching method (t-Ti3C2), the h-Ti3C2 has the higher c lattice parameter, larger interlayer distance and larger BET specific surface area, because of the slow release mechanism during the hydrothermal process. The hydrothermal etching method not only avoided the use of high-concentration HF, but also was more efficient to prepare Ti3C2 flakes. Moreover, the hydrothermal etching route can be extended to other MXene materials, e.g. Nb2C. We demonstrated that the h-MXenes have better adsorption performance of methylene blue and methyl orange dyes. The hydrothermal etching route proposed in this study enabled the environmental benign and high efficiency exfoliation of MXenes, displaying the promise to facilely prepare 2D MXenes and paving a way to their widespread applications.

Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor the silk protein conformation in a range of single natural silk fibers (domestic and wild silkworm and spider dragline silk). With the selection of suitable aperture size, we obtained high-resolution S-FTIR spectra capable of semiquantitative analysis of protein secondary structures. For the first time, we have determined from S-FTIR the β-sheet content in a range of natural single silk fibers, 28 ± 4, 23 ± 2, and 17 ± 4% in Bombyx mori, Antheraea pernyi, and Nephila edulis silks, respectively. The trend of β-sheet content in different silk fibers from the current study accords quite well with published data determined by XRD, Raman, and (13)C NMR. Our results indicate that the S-FTIR microspectroscopy method has considerable potential for the study of single natural silk fibers.

A strategy to prepare doxorubicin-loaded magnetic silk fibroin nanoparticles is presented. The nanoparticles serve as a nanometer-scale drug-delivery system in the chemotherapy of multidrug-resistant cancer under the guidance of a magnetic field. The magnetic tumor-targeting ability broadens the range of biomedical applications of silk fibroin, and the nanoparticle-assisted preparation strategy is useful for the advancement of other biomacromolecule-based materials.

Usually, regenerated silk fibroin (RSF) hydrogels cross-linked by chemical agents such as horseradish peroxide (HRP)/H2O2 perform elastic properties, while display unsatisfactory strength for practical applications especially as load-bearing materials, and inadequate stability when incubated in a simulated in vivo environment. Here, the RSF hydrogel with both excellent strength and elasticity was prepared by inducing the conformation transition from random coil to β-sheet in a restricted RSF network precross-linked by HRP/H2O2. Such "dual-networked" hydrogels, regarding the one with 10 wt % RSF (Mw: 220 kDa) as a representative, show around 100% elongation, as well as the compressive modulus and tensile modulus up to 3.0 and 2.5 MPa respectively, which are much higher than those of physically cross-linked natural polymer hydrogels (commonly within 0.01-0.1 MPa at the similar solid content). It has been shown that the enhanced comprehensive mechanical properties of RSF hydrogels derive from the formation of small-sized and uniformly distributed β-sheet domains in the hydrogel during the conformation transition of RSF whose size is limited by the first network formed by cross-linkers with HRP/H2O2. Importantly, the tough RSF hydrogel changes the normally weak recognition of various RSF hydrogels and holds a great potential to be the material in biomedical field because it seems to be very promising regarding its biocompatibility, biodegradability, etc.

In this study, we examined the efficacy of nine different types of coconut-fiber derived biochars (CFBs), prepared at different temperatures and chemically modified with ammonia, hydrogen peroxide and nitric acid, to remove lead (Pb2+) from aqueous solutions. Langmuir-qm values of the biochars pyrolyzed at 300°C and modified with ammonia and nitric acid increased from 49.5 to 105.5 and 85.2mgg-1, respectively, compared to control (unmodified), whereas hydrogen peroxide treatment had no effect. The maximum amount of Pb adsorbed on biochars was in the order of CFB-700>MCFB-300-NH3·H2O>CFB-500>MCFB-300-HNO3>CFB-300. X-ray absorption fine structure (XAFS) spectroscopy results revealed that Pb-montmorillonite, Pb(C2H3O2)2, PbSO4, Pb-Al2O3 and Pb3(PO4)2 were the five most important Pb species observed in Pb-loaded biochars, and as such, favoring Pb immobilization in aqueous solutions. Overall, the sorption capacity of CFBs pyrolyzed at 300°C substantially increased for Pb2+ with ammonia and nitric acid modification. However, these chemical modifications did not improve the sorption of Pb on CFBs pyrolyzed at temperatures ≥500°C, thereby highlighting a temperature dependent response of chemically modified biochars to Pb sorption in this study.

A hydrogel based on a sustainable plant protein was fabricated to remove copper ions from wastewater and recycle them, making the environment and resources sustainable.

Natural biomaterials are extensively used in tissue engineering due to their microstructure interconnectivity and inherent bioactivity which mimics of natural extracellular matrix (ECM), supporting cell infiltration, adhesion, differentiation, transportation of oxygen and nutrient, finally restoring the structure and function of defective tissues or organs. Microstructure, mechanical properties, biostability and cellular activity of natural biomaterials are controlled via blending of natural or natural with synthetic biopolymers and physical/chemical crosslinking treatments to allow the required mechanical strength, degradation rate and ECM mimic microenvironment for supporting of cellular activity. In addition, natural biomaterials also performed a key role in delivery of cells, bioactive molecules, growth factors and drugs. In this review, we will explore the fabrication, challenges and applications of natural biomaterials for various tissues engineering issues, including polymer selection, fabrication techniques, microstructure manipulation, physical/chemical crosslinking, mechanical properties, biostability as well as their role in delivery of cells, bioactive molecules, growth factors and drugs.

C2H4 is the most important and demanded chemical raw materials. Separating C2H6 from C2H4 using C2H6-trapping adsorbents to lower the energy consumption in the petrochemical industry is important but challenging. This review summarizes the research progresses on the development of C2H6-selective metal–organic frameworks (MOFs), covalent-organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), porous organic cages (POCs), carbon-based materials, and zeolites for C2H6/C2H4 separation. The C2H6 uptakes, C2H6/C2H4 selectivities, stability, cost, scale-up synthesis, regeneration performance and shaping of C2H6-selective MOFs are overviewed. The strategies for enhancing C2H6 uptakes, C2H6/C2H4 selectivities and moisture stability on MOFs are summarized. The mechanism underlying the preferential adsorption of C2H6 over C2H4 on different adsorbents is also highlighted. Additionally, challenges and future developments of various C2H6-selective adsorbents are discussed.

The ethanol-induced conformation transition of regenerated Bombyx mori silk fibroin membrane from a poorly defined to the well ordered state was monitored by time-resolved Fourier transform infrared spectroscopy (FTIR) for the first time. From the analysis of FTIR difference spectra, taken on time scales as short as 6 s and up to 1 h after addition of ethanol, intensity vs. time plots of an increasing band at 1618 cm−1 were observed indicating formation of a β-sheet coincident with the loss of intensity of a band at 1668 cm−1 indicating decreases of random coil and/or silk I structure. Both infrared markers were fitted with identical biphasic exponential decay functions, however, there was a clear burst phase occurring prior to the onset of the observed transitions. The conformation transition process is indicated to either proceed sequentially through (at least) two intermediate states that contain different levels of β-sheet structure or to have parallel pathways of initial β-sheet formation followed by a slower ‘perfection’ phase. The first observed process forms in a burst phase a few seconds after mixing (or even faster), prior to the collection of the first spectrum at 6 s. The second observed process occurs with a time constant of ∼0.5 min, the intermediate present at this stage then continues with a time constant of 5.5 min completing the observed formation of the β-sheet. The conformation transition of this slower intermediate is not only indicated by an analysis of the kinetics of the random coil and β-sheet-specific bands discussed above, it roughly coincides with the appearance of an additional infrared marker at 1695 cm−1, which may be a marker for β-sheet structure specific to the formation of the perfected structure. The conformation transition of this protein analyzed by infrared spectroscopy provides insight into a part of the fascinating process of cocoon formation in B. mori.

Several different solvent systems are commonly used to dissolve Bombyx mori silk fibroin to prepare regenerated silk membranes and fibers though differences in the behavior of these solvents have not been fully investigated. Here we compare the effects of four of these on the rheology of silk fibroin solutions and on protein secondary structure as revealed by FTIR spectroscopy of cast membranes. The results demonstrated that Ca(NO3)2–MeOH–H2O and LiBr–EtOH–H2O had the strongest solvation on the silk fibroin chains, which showed an almost constant viscosity (Newtonian behavior) over most of the shear rate range (0.1–500 s−1). In contrast, the 9.5 M aqueous LiBr appeared to have the weakest solvation with similar effects on the silk fibroin molecules to pure water as indicated by rheological behavior. It was also found that the silk fibroin membranes prepared using all four solvent system showed mainly random coil conformation with a small proportion of β-sheet by FTIR spectroscopy. We discuss the implications of these findings for the preparation of regenerated silk for different applications.

Advanced MaterialsVolume 21, Issue 3 p. 366-370 Communication Silk Fibers Extruded Artificially from Aqueous Solutions of Regenerated Bombyx mori Silk Fibroin are Tougher than their Natural Counterparts Guanqiang Zhou, Guanqiang Zhou The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorZhengzhong Shao, Zhengzhong Shao The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorDavid P. Knight, David P. Knight Department of Zoology, University of Oxford South Parks Road, Oxford OX1 3PS (UK)Search for more papers by this authorJiaping Yan, Jiaping Yan The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorXin Chen, Corresponding Author Xin Chen [email protected] The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China).Search for more papers by this author Guanqiang Zhou, Guanqiang Zhou The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorZhengzhong Shao, Zhengzhong Shao The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorDavid P. Knight, David P. Knight Department of Zoology, University of Oxford South Parks Road, Oxford OX1 3PS (UK)Search for more papers by this authorJiaping Yan, Jiaping Yan The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)Search for more papers by this authorXin Chen, Corresponding Author Xin Chen [email protected] The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China)The Key Laboratory of Molecular Engineering of Polymers of MOE Department of Macromolecular Science Laboratory of Advanced Materials Fudan University 220 Handan Road, Shanghai, 200433 (PR China).Search for more papers by this author First published: 12 January 2009 https://doi.org/10.1002/adma.200800582Citations: 165AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Regenerated silk fibers extruded from fibroin solutions are highly lustrous and have uniform diameters and circular cross-sections. They are stronger, more extensible, and tougher than natural silkworm silk. These fibers can be spun under clean, sterile, and carefully regulated conditions, and may permit direct incorporation of drugs for controlled release, being suitable for biomedical applications. Citing Literature Supporting Information Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Filename Description adma_200800582_sm_supplfigs.pdf78 KB supplfigs Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume21, Issue3January 19, 2009Pages 366-370 RelatedInformation

Abstract Time‐resolved FTIR analysis was used to monitor the conformation transition induced by treating regenerated Bombyx mori silk fibroin films and solutions with different concentrations of ethanol. The resulting curves showing the kinetics of the transition for both films and fibroin solutions were influenced by the ethanol concentration. In addition, for silk fibroin solutions the protein concentration also had an effect on the kinetics. At low ethanol concentrations (for example, less than 40% v/v in the case of film), films and fibroin solutions showed a phase in which β‐sheets slowly formed at a rate dependent on the ethanol concentration. Reducing the concentration of the fibroin in solutions also slowed the formation of β‐sheets. These observations suggest that this phase represents a nucleation step. Such a nucleation phase was not seen in the conformation transition at ethanol concentrations &gt; 40% in films or &gt; 50% in silk fibroin solutions. Our results indicate that the ethanol‐induced conformation transition of silk fibroin in films and solutions is a three‐phase process. The first phase is the initiation of β‐sheet structure (nucleation), the second is a fast phase of β‐sheet growth while the third phase represents a slow perfection of previously formed β‐sheet structure. The nucleation step can be very fast or relatively slow, depending on factors that influence protein chain mobility and intermolecular hydrogen bond formation. The findings give support to the previous evidence that natural silk spinning in silkworms is nucleation‐dependent, and that silkworms (like spiders) use concentrated silk protein solutions, and careful control of the pH value and metallic ion content of the processing environment to speed up the nucleation step to produce a rapid conformation transition to convert the water soluble spinning dope to a tough solid silk fiber. Proteins 2007. © 2007 Wiley‐Liss, Inc.

The objective of the present study is to investigate the possibility of preparing pure protein microspheres from regenerated silk fibroin (RSF). It is found that RSF microspheres, with predictable and controllable sizes ranging from 0.2 to 1.5 µm, can be prepared via mild self-assembling of silk fibroin molecular chains. The merits of this novel method include a rather simple production apparatus and no potentially toxic agents, such as surfactants, initiators, cross-linking agents, etc. The results show that the particle size and size distribution of RSF microspheres are greatly affected by the amount of ethanol additive, the freezing temperature and the concentration of silk fibroin. Finally, the mechanism of RSF microspheres formation is also discussed based on our experimental results.

Natural polymer Bombyx mori silk fibroin is used as a biotemplate to produce silver nanoparticles in situ under light (both incandescent light and sunlight) at room temperature. Silk fibroin provides multiple functions in the whole reaction system, serving as the reducing agent of silver, and the dispersing and stabilizing agent of the resulted silver nanoparticles. As the reaction needs not any other chemicals and only uses light as power source, the synthetic route of silver nanoparticles reported here is rather environment-friendly and energy-saving. The silk fibroin-silver nanoparticle composite prepared by this method can be stably stored in a usual environment (room temperature, exposure to light, and so forth) for at least one month. Such a silk fibroin-silver nanoparticle composite shows an effective antibacterial activity against the methicillin-resistant Staphylococcus aureus (S. aureus) and subsequently inhibits the biofilm formation caused by the same bacterium. Moreover, a maturely formed biofilm created by methicillin-resistant S. aureus can be destroyed by the silk fibroin-silver nanoparticle composite, which meets the demand of clinical application. Therefore, the silk fibroin-silver nanoparticle composite prepared by this clean and facile method is expected to be an effective and economical antimicrobial material in biomedical fields.

An amphoteric hydrogel film was prepared by solution blending of two natural polyelectrolytes, chitosan and carboxymethylcellulose, and cross-linking with glutaraldehyde. The bending of the film in an electric field was studied in different electrolyte solutions. Because of its amphoteric nature, the hydrogel can bend toward either anode or cathode depending on the pH of the solution. Other factors such as ionic strength and electric field strength also influence the electromechanical behavior of the hydrogels. The equilibrium bending angle of the hydrogel was found to reach a maximum at about 90 degrees in pH = 6 Britton-Robinson buffer solution with an ionic strength of 0.2 M. The sensitivity of the films over a wide range of pH and the good reversibility of this natural amphoteric electric-sensitive hydrogel suggest its future use in microsensor and actuator applications, especially in the biomedical field.

A protein conformation transition from random coil and/or helical conformation to β-sheet is known to be central to the process used by silk-spinning spiders and insects to convert concentrated protein solutions to tough insoluble threads. Several factors including pH, metallic ions, shear force, and/or elongational flow can initiate this transition in both spiders and silkworms. Here, we report the use of proton induced X-ray emission (PIXE), inductively coupled plasma mass spectroscopy (ICP-MS) and atomic adsorption spectroscopy (AAS) to investigate the concentrations of six metal elements (Na, K, Mg, Ca, Cu, and Zn) at different stages in the silk secretory pathway in the Bombyx mori silkworm. We also report the use of Raman spectra to monitor the effects of these six metallic ions on the conformation transition of natural silk fibroin dope and concentrated regenerated silk fibroin solution at concentrations similar to the natural dope. The results showed that the metal element contents increased from the posterior part to the anterior part of silk gland with the exception of Ca which decreased significantly in the anterior part. We show that these changes in composition can be correlated with (i) the ability of Mg2+, Cu2+, and Zn2+ to induce the conformation transition of silk fibroin to β-sheet, (ii) the effect of Ca2+ in forming a stable protein network (gel), and (iii) the ability of Na+ and K+ to break down the protein network.

Combination of proteins with other nanomaterials offers a promising strategy to fabricate novel hybrids with original functions in biology, medicine, nanotechnology, and materials science.Under carefully selected experimental conditions, we show that graphene nanosheets are able to direct one-dimensional self-assembly of silk fibroin, forming an unprecedented type of nanohybrids.These silk/graphene hybrids combine physical properties of both constituents and form functional composites with well-ordered hierarchical structures.Due to the facile fabrication process and their tunable nanostructures, the resultant hybrids show promise in applications as diverse as tissue engineering, drug delivery, nanoelectronics, nanomedicine, biosensors, and functional composites.

Regenerated silk fibroin (RSF) fibers were obtained by extruding a concentrated aqueous silk fibroin solution into an ammonium sulfate coagulation bath. A custom-made simplified industrial-type wet-spinning device with continuous mechanical postdraw was used. The effect of dope concentration, coagulation bath, extrusion rate, and postdraw treatment on the morphology of RSF fiber was examined. The results showed that although RSF fiber could be formed with dope concentration between 13 and 19% (w/w), the ones spun from 15% RSF solution showed the most regular morphology being dense and homogeneous in cross-section with a smooth surface and a uniform cylindrical shape. Though it had little effect on morphology, postdraw treatment especially under steam, significantly improved the mechanical properties of the RSF fibers.

Amyloid fibrils and silk fibroin (SF) fibrils are proteinaceous aggregates occurring either naturally or as artificially reconstituted fibrous systems, in which the constituent β-strands are aligned either orthogonally or parallel to the fibril main axis, conferring complementary physical properties. Here, it is shown how the combination of these two classes of protein fibrils with orthogonally oriented β-strands results in composite materials with controllable physical properties at the molecular, mesoscopic, and continuum length scales. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Regenerated silk fibroin (RSF) of Bombyx mori silk fiber is a promising natural material for bone defect repair. However, a lack of specific integrin and growth factor for osteoinduction significantly hinders its application in this area. In this study, the role of Laponite nanoplatelet (LAP), a bioactive clay that can promote osteoblast growth, in the formation of RSF hydrogel, as well as the various properties of RSF/LAP hybrid hydrogel, was closely investigated. The results indicate that LAP could serve as a medium to accelerate hydrophobic interaction among the RSF molecules and a disruptor to limit the growth of β-sheet domain during the gelation of RSF. Rheological measurement suggests that the RSF/LAP hydrogel is injectable as it displays thixotropy in the room temperature. Proliferation and differentiation results of the primary osteoblasts encapsulated in hydrogel show that RSF/LAP hydrogel can promote the cell proliferation and enhance the osteogenic differentiation. The transcript levels for alkaline phosphatase, osteocalcin, osteopontin, and collagen type I osteogenic markers obviously improve with RSF/LAP hydrogel compared to the controls at 14 days, especially with the higher contents of LAP. Overall, the results suggest that the RSF/LAP hydrogel have great potential to be utilized as an injectable biomaterial for irregular bone defect repair.

Abstract Antheraea pernyi ( A. pernyi ) silk is produced and used by “wild” silkworms to construct a cocoon, but the primary structure of its protein is rather similar to that of spider major ampullate silk used to build web and dragline. Studies on this specific silk may provide valuable knowledge about the structure‐property relationship for the whole animal silk family. In this work, A. pernyi silk fibers with few macroscale defects are obtained by forcibly reeling, and are investigated in detail. It is found that such silk fibers display breaking stress and toughness of the same magnitude as spider major ampullate silks and forcibly reeled mulberry silk. The other mechanical properties, such as elasticity, supercontraction, and the effect of water on modulus are between those of spider major ampullate silks and mulberry silk. Therefore, an interpretation of the connection between the primary structures of silk proteins and the mechanical properties of silks is proposed here based on the ordered fraction, which in turn is determined by both the protein sequence and spinning process of the silk.

Spider silk is one of the best natural fibers and has superior mechanical properties. However, the large-scale harvesting of spider silk by rearing spiders is not feasible, due to their territorial and cannibalistic behaviors. The silkworm, Bombyx mori, has been the most well known silk producer for thousands of years and has been considered an ideal bioreactor for producing exogenous proteins, including spider silk. Previous attempts using transposon-mediated transgenic silkworms to produce spider silk could not achieve efficient yields, due to variable promoter activities and endogenous silk fibroin protein expression. Here, we report a massive spider silk production system in B. mori by using transcription activator-like effector nuclease-mediated homology-directed repair to replace the silkworm fibroin heavy chain gene (FibH) with the major ampullate spidroin-1 gene (MaSp1) in the spider Nephila clavipes We successfully replaced the ∼16-kb endogenous FibH gene with a 1.6-kb MaSp1 gene fused with a 1.1-kb partial FibH sequence and achieved up to 35.2% chimeric MaSp1 protein amounts in transformed cocoon shells. The presence of the MaSp1 peptide significantly changed the mechanical characteristics of the silk fiber, especially the extensibility. Our study provides a native promoter-driven, highly efficient system for expressing the heterologous spider silk gene instead of the transposon-based, random insertion of the spider gene into the silkworm genome. Targeted MaSp1 integration into silkworm silk glands provides a paradigm for the large-scale production of spider silk protein with genetically modified silkworms, and this approach will shed light on developing new biomaterials.

In the clinic, bone defects resulting from infections, trauma, surgical resection and genetic malformations remain a significant challenge. In the field of bone tissue engineering, three-dimensional (3D) scaffolds are promising for the treatment of bone defects. In this study, calcium sulfate hydrate (CSH)/mesoporous bioactive glass (MBG) scaffolds were successfully fabricated using a 3D printing technique, which had a regular and uniform square macroporous structure, high porosity and excellent apatite mineralization ability. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were cultured on scaffolds to evaluate hBMSC attachment, proliferation and osteogenesis-related gene expression. Critical-sized rat calvarial defects were applied to investigate the effect of CSH/MBG scaffolds on bone regeneration in vivo. The in vitro results showed that CSH/MBG scaffolds stimulated the adhesion, proliferation, alkaline phosphatase (ALP) activity and osteogenesis-related gene expression of hBMSCs. In vivo results showed that CSH/MBG scaffolds could significantly enhance new bone formation in calvarial defects compared to CSH scaffolds. Thus 3D printed CSH/MBG scaffolds would be promising candidates for promoting bone regeneration.

Collagen hydrogel has been regarded as an excellent biomaterial because it is an abundant and sustainable resource and has good biocompatibility and controllable cell-based biodegradability. However, the poor mechanical properties of collagen hydrogel are the main disadvantage preventing it from having wide applications. In this communication, we use aldehyde-functionalized dextran, which is prepared from the oxidation of another natural polymer dextran, as a macromolecular cross-linker to enhance the strength of the collagen hydrogel. The resulting collagen/aldehyde-functionalized dextran (Col/DAD) hydrogels are much stronger and show better thermostability than the pristine collagen hydrogel, as expected. The maximum compressive strength of the Col/DAD hydrogel is 32.5 ± 1.6 kPa, which is about 20 times more than that of the pristine collagen hydrogel. We also prove that our method maintains the good biocompatibility of the collagen hydrogel and does not bring the cytotoxicity often observed from conventional chemical cross-linking in the product. Therefore, the strong collagen hydrogel made by oxidized dextran modification may have a great potential in tissue engineering and other biomedical fields.

To better understand the influence of structure and surface properties of NCMs towards REE, requires individual research for each NCM. The adsorption/extraction for light (La3+) and heavy (Yb3+) REE of kaolinite (Kao), montmorillonite (Mt), muscovite (Ms), illite (Ilt), were systematically investigated and compared. Additionally, all the NCMs were fully characterized by XRD, XRF, XPS, Zeta potential and nitrogen adsorption-desorption isotherms to build the relationship between adsorption/extraction mechanism and minerals' property. Our experiments show that the Mt. exhibits highest adsorption and regeneration efficiencies for both La3+ and Yb3+ and decrease in the order of Mt > Ms > Ilt > Kao, while Kao has highest extractions efficiencies for both REE in the order of Kao > Ilt > Mt > Ms 89% for La3+ and 85% for Yb3+ were achieved from Kao and the lowest extractions were obtained from Ms. (63% for La3+ and 57% for Yb3+). The lack of Ms. on both reuse and extraction characteristics is believed to be related to presence of iron oxide associated with Ms. In addition, the important role of the pH in extraction of REE from NCMs was evidenced, when REE-NCMs come into contact with the NH4+ solution, the pH is rapidly increased over initial pH solution for both Mt. and Ms., thus leading to the decrease of the availability of ion-exchangeable REE with NH4+ions. The results illustrated that the structure and surface properties of NCMs are also the key factors that affect the rare earth leaching, thus identifying the types of NCMs and associated impurities in clay materials are important, either for getting the best leaching system or in developing a new one.

Waste residues produced by agricultural and forestry industries can generate energy and are regarded as a promising source of sustainable fuels. Pyrolysis, where waste biomass is heated under low-oxygen conditions, has recently attracted attention as a means to add value to these residues. The material is carbonized and yields a solid product known as biochar. In this study, eight types of biomass were evaluated for their suitability as raw material to produce biochar. Material was pyrolyzed at either 350 °C or 500 °C and changes in ash content, volatile solids, fixed carbon, higher heating value (HHV) and yield were assessed. For pyrolysis at 350 °C, significant correlations (p &lt; 0.01) between the biochars’ ash and fixed carbon content and their HHVs were observed. Masson pine wood and Chinese fir wood biochars pyrolyzed at 350 °C and the bamboo sawdust biochar pyrolyzed at 500 °C were suitable for direct use in fuel applications, as reflected by their higher HHVs, higher energy density, greater fixed carbon and lower ash contents. Rice straw was a poor substrate as the resultant biochar contained less than 60% fixed carbon and a relatively low HHV. Of the suitable residues, carbonization via pyrolysis is a promising technology to add value to pecan shells and Miscanthus.

Flexible ionic conductive hydrogel is attracting significant interest as it could be one of the crucial components for multifunctional ionotronic devices. However, their features of inevitably drying out without package and freezing at subzero temperatures may greatly limit the applications of conventional hydrogels in specific situations. Here, we present an ionic conductive hydrogel with water retention and freezing tolerance that consists of silk fibroin, ionic liquid, water, and inorganic salt. It is discovered that the ionic liquid serves multiple purposes to prevent water evaporation, decrease the freezing point, provide the essential conductivity of the hydrogel, etc. As a binary mixed solvent, the ionic liquid/water mixture enhances both water retention and freezing tolerance of the hydrogel electrolyte. Based on the silk fibroin (SF)/1-ethyl-3-methylimidazolium acetate (EMImAc)/H2O/KCl hydrogel electrolyte, the flexible fiberlike supercapacitor could still function well at a temperature as low as −50 °C and after being stored in the open air for a long time. It is anticipated that this hydrogel will prove useful in developing new applications operating under harsh environments.

Angiogenesis-osteogenesis coupling processes are vital in bone tissue engineering. Normal biomaterials implanted in bone defects have issues in the sufficient formation of blood vessels, especially in the central part. Single delivery of vascular endothelial growth factors (VEGF) to foci in previous studies did not show satisfactory results due to low loading doses, a short protein half-life and low efficiency. Development of a hypoxia-mimicking microenvironment for cells by local prolyl-4-hydroxylase inhibitor release, which can stabilize hypoxia-inducible factor 1α (HIF-1α) expression, is an alternative method. The aim of this study was to design a dimethyloxallyl glycine (DMOG) delivering scaffold composed of mesoporous bioactive glasses and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) polymers (MPHS scaffolds), so as to investigate whether the sustained release of DMOG promotes local angiogenesis and bone healing. The morphology and microstructure of composite scaffolds were characterized. The DMOG release patterns from scaffolds loaded with different DMOG dosages were evaluated, and the effects of DMOG delivery on human bone marrow stromal cell (hBMSC) adhesion, viability, proliferation, osteogenic differentiation and angiogenic-relative gene expressions with scaffolds were also investigated. In vivo studies were carried out to observe vascular formations and new bone ingrowth with DMOG-loaded scaffolds. The results showed that DMOG could be released in a sustained manner over 4 weeks from MPHS scaffolds and obviously enhance the angiogenesis and osteogenesis in the defects. Microfil perfusion showed a significantly increased formation of vessels in the defects with DMOG delivery. Furthermore, micro-CT imaging and fluorescence labeling indicated larger areas of bone formation for DMOG-loaded scaffolds. It is concluded that MPHS-DMOG scaffolds are promising for enhancing bone healing of osseous defects.

Highly efficient visible-light-responsive Z-Scheme CuBi2O4/Ag3PO4 photocatalysts were prepared by a hydrothermal synthesis and in-situ deposition method and characterized comprehensively. Under visible-light irradiation, the photocatalytic performance of CuBi2O4/Ag3PO4 in the degradation of diclofenac sodium (DS) in aqueous solutions was studied under different conditions such as different catalyst composition, solution pH, and concentration of S2O82- or H2O2, and the response surface methodology (RSM) was used to analyze the interaction effect of the parameters. The optimal activity of CuBi2O4/Ag3PO4 was achieved at the mass ratio of 3:7 and pH of 4.42. Moreover, the introduced S2O82- could significantly enhance the catalytic activity of CuBi2O4/Ag3PO4; when 1 mM S2O82- was added to the catalytic system, 10 mg/L of DS could be completely degraded within 60 min, but the structure of CuBi2O4/Ag3PO4 was severely destroyed. While when H2O2 was introduced into the system, both the activity and stability of CuBi2O4/Ag3PO4 were improved significantly. Finally, the photodegradation pathway of DS is proposed and the photocatalytic mechanism of CuBi2O4/Ag3PO4 under different conditions is explained. CuBi2O4/Ag3PO4 and CuBi2O4/Ag3PO4 (S2O82-) photocatalytic systems follow the Z-Scheme theory, and Ag0 formed on the surface of catalyst serves as the recombination center for the photogenerated e- from the conduction band (CB) of Ag3PO4 and h+ from the valence band (VB) of CuBi2O4; meanwhile, the catalytic degradation of DS by CuBi2O4/Ag3PO4 in the presence of H2O2 follows the heterojunction energy band theory.

Particulate plastics (<5 mm), including macroplastics (1 μm to 5 mm), microplastics (100 nm to 1 μm) and nanoplastics (<100 nm), have become a global environmental problem due to their widespread occurrence, distribution and ecosystem risk. Although numerous studies on particulate plastics have been conducted in aquatic systems, investigations in the soil ecosystem are lacking. Soil is the main storage place of particulate plastics, conferring significant impacts on plant growth and development. The impact of particulate plastics on plants is directly related to the safety of agricultural products. This review comprehensively examines the pollution characteristics and exposure pathways of particulate plastics in agricultural soils, highlighting plastic uptake process, and mechanisms in plants, and effects of particulate plastics, biodegradable particulate plastics and combined pollution of plastics with other environmental pollutants on plant performances. This review identifies a number of future research prospects including the development of accurate quantitative methods for plastic analysis in soil and plant samples, understanding the environmental behaviors of conventional and biodegradable particulate plastics in the presence and absence of other environmental pollutants, unravelling the fate of particulate plastics in plants, phyto-toxicity and molecular regulatory mechanisms of particultate plastics, and developing best management practices for the production of safe agricultural products in plastic-contaminated soils.

A highly stretchable and anti-freezing RSF/CaCl₂/HRP conductive hydrogel can be fabricated into a transparent strain/temperature dual sensing ionotronic skin to detect human movements in a wide temperature range.

Arsenic (As) is a potentially toxic element (PTE) that causes adverse effects on human health through contamination of soil and groundwater worldwide. Biochar has captured great interest as an amendment for improving soil fertility, immobilizing PTEs, and being a carbon stabilizer. However, unlike other cationic PTEs, pristine biochar has shown unsatisfactory results for soil As immobilization, owing to increased soil pH and accompanying electrostatic repulsion between the biochar surface and As anions. Complex soil conditions due to dynamically variable dissolved organic matter concentration, redox potential, and pH significantly influence the As immobilization capacity of biochar. To overcome the above drawbacks and improve As immobilization performance, recent studies have proposed biochar modification in various ways. This review summarizes the latest studies on modified biochar for As immobilization in soil, focusing on modification methods and performance evaluation. Limitations and perspectives of key biochar modification methods are critically discussed, advancing our understanding of the underpinned science for designing biochar to achieve increased stability for long-term application. The collated information will help environmental policymakers and stakeholders in predicting the benefits and future directions of modified biochar research for the immobilization of As and other PTEs.

The spinning mechanism of natural silk has been an open issue. In this study, both the conformation transition from random coil to β sheet and the β sheet aggregation growth of silk fibroin are identified in the B. mori regenerated silk fibroin aqueous solution by circular dichroism (CD) spectroscopy. A nucleation‐dependent aggregation mechanism, similar to that found in prion protein, amyloid β (Aβ) protein, and α‐synuclein protein with the conformation transition from a soluble protein to a neurotoxic, insoluble β sheet containing aggregate, is a novel suggestion for the silk spinning process. We present evidence that two steps are involved in this mechanism: (a) nucleation, a rate‐limiting step involving the conversion of the soluble random coil to insoluble β sheet and subsequently a series of thermodynamically unfavorable association of β sheet unit, i.e. the formation of a nucleus or seed; (b) once the nucleus forms, further growth of the β sheet unit becomes thermodynamically favorable, resulting a rapid extension of β sheet aggregation. The aggregation growth follows a first order kinetic process with respect to the random coil fibroin concentration. The increase of temperature accelerates the β sheet aggregation growth if the β sheet seed is introduced into the random coil fibroin solution. This work enhances our understanding of the natural silk spinning process in vivo .

We report the results of an investigation into the rheology of solutions of natural spider silk dope (spinning solution). We demonstrate that dilute dope solutions showed only shear thinning as the shear rate increased while more concentrated solutions showed an initial shear thinning followed by a shear thickening and a subsequent decline in viscosity. The critical shear rate for shear thickening depended on dope concentration and was very low in concentrated solutions. This helps to explain how spiders are able to spin silk at very low draw rates and why they use a very concentrated dope solution. We also show that the optimum shear rate for shear thickening in moderately concentrated solutions occurred at pH 6.3 close to the observed pH at the distal end of the spider's spinning duct. Finally, we report that the addition of K(+) ions to dilute dope solutions produced a spontaneous formation of nanofibrils that subsequently aggregated and precipitated. This change was not seen after the addition of other common cations. Taken together, these observations support the hypothesis that the secretion of H(+) and K(+) by the spider's duct together with moderate strain rates produced during spinning induce a phase separation in the silk dope in which the silk protein (spidroin) molecules are converted into insoluble nanofibrils.

Fluorescence and circular dichroism spectroscopy were used to monitor the conformational transition of regenerated Bombyx mori silk fibroin (RSF) in aqueous solutions under different conditions. According to the analysis of fluorescence spectra using anilinonaphthalene-8-sulfonic acid magnesium salt (ANS) as an external probe, the destruction of the hydrophobic core prior to the secondary structure change suggests that this collapse may initiate the conformational transition from random coil to beta-sheet for RSF. The temperature dependence of the structural changes of RSF, detected by both fluorescence spectroscopy and circular dichroism, shows a reversible process upon heating and recooling, with the midpoint around 45 degrees C. The results also indicate that most of the tryptophan (Trp) residues contained in silk fibroin are concentrated on the surface of the unfolded protein. However, they will change their location in the highly ordered structure (e.g., becoming more homogeneous) with the conformational transition of silk fibroin. Moreover, our studies also suggest that the presence of water plays a crucial role during the structure changes of fibroin.

This study showed that Bombyx mori silk protein could be selectively induced to fold into fibrils dominated by either cross- or parallel-β-sheet structure, where the β-strands arrange perpendicular or parallel to the long fibril axis, incubated in ethanol–water quiescently or in water under shear.

Silk nanofibers were successfully prepared by electrospinning an aqueous solution of regenerated silk fibroin (RSF, from Bombyx mori) with higher molecular weight. Many factors, such as concentration, electrical conductivity of the fibroin solution and applied electric field were found to influence the morphology of these nanofibers. The conformation of RSF nanofibers was transformed from random coil/helical to β-sheet after the post treatment with pure ethanol. Under optimal conditions, the as-spun non-woven mats achieved good mechanical properties. The apparent stress and strain at break were 11.1 ± 0.7 MPa and 10.2 ± 1.6%, respectively, which is important for the application of such a unique fibrous protein.

The conformation and eventual morphology of silk fibroin (SF) chains are crucial for the mechanical properties of SF materials, and are strongly related to the solvation step as a key stage in their processing conditions. In this work, a novel SF/AmimCl (1-allyl-3-methylimidazolium chloride) solution with unique properties is reported and compared with conventional regenerated SF aqueous solutions, based on an investigation of its rheological properties. The steady shearing behavior suggested that AmimCl is a good solvent for SF molecules, and shear thinning of semidiluted SF/AmimCl solution at high shear rates showed behavior similar to that in native spinning, which is due to the rearrangement and orientation of SF molecular chains. Fitting of experimental dynamic viscoelastic data to the Rouse model provided an effective method to estimate the molecular weight of SF. We believe that this work not only provides a better understanding of the relationship between properties of silk protein and aggregation states of their molecular chains, but also provides tools to fabricate high-performance SF-based materials.

A silica-based mesoporous nanosphere (MSN) controlled-release drug delivery system has been synthesized and characterized. The system uses L-cysteine derivatized gold nanoparticles (AuNPs), bound to the MSNs using Cu2+ as a bridging ion. The AuNPs serve as removable caps that hinder the release of drug molecules inside the amino functionalized MSN mesoporous framework. The modified MSNs themselves exhibit negligible cytotoxicity to living cells, as revealed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The drug delivery system requires one of two biological stimuli to trigger drug release. These stimuli are either: low pH (pH < 5); or elevated levels of adenosine triphosphate (ATP) (concentration > 4 mM). The feasibility of biologically controlled release was demonstrated through the stimuli-induced removal of the AuNP caps over the MSN releasing the anticancer drug doxorubicin. We envisage that this MSN system could play a significant role in developing new generations of controlled-release delivery vehicles.

Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor both protein secondary structures (conformations) and their orientations in single cocoon silk fibers of the Chinese Tussah silk moth (Antheraea pernyi). In addition, to understand further the relationship between structure and properties of single silk fibers, we studied the changes of orientation and content of different secondary structures in single A. pernyi silk fibers when subjected to different strains. The results showed that the content and orientation of β-sheet was almost unchanged for strains from 0 to 0.3. However, the orientation of α-helix and random coil improved progressively with increasing strain, with a parallel decrease in α-helix content and an increase in random coil. This clearly indicates that most of the deformation upon stretching of the single fiber is due to the change of orientation in the amorphous regions coupled with a conversion of some of the α-helix to random coil. These observations provide an explanation for the supercontraction behavior of certain animal silks and are likely to facilitate understanding and optimization of postdrawing used in the conjunction with the wet-spinning of silk fibers from regenerated silk solutions. Thus, our work demonstrates the power of S-FTIR microspectroscopy for studying biopolymers.

Silk protein is a promising natural material applied in various fields, but the application of silk protein-based hydrogel is quite limited because of its long gelation time and poor mechanical properties. Here, we present a facile way to prepare strong silk protein hydrogels simply by adding surfactant into silk fibroin aqueous solution and incubating at 60 °C. The resulting silk protein hydrogels demonstrate fairly good mechanical properties; for example, the silk protein hydrogel made by adding sodium dodecyl sulfate (SDS) has the compressive and tensile moduli of 3.0 and 3.3 MPa, respectively, which are close to some tissues in the body, such as cartilages, tendons, and ligaments. The effect of different types of surfactant on the formation of strong silk protein hydrogel, and the possible reason for the improvement of the mechanical properties of the hydrogel are also discussed. In addition, we show that such a strong silk protein hydrogel maintains good biocompatibility when adding a proper amount of surfactant. Finally, we use a Fe3O4-loaded silk protein hydrogel as an example to demonstrate its application in the catalytic field. All these results imply that such a natural, sustainable, strong, and biocompatible protein-based hydrogel holds great promise as a multifunctional material in various applications.

A novel way is provided to harvest a high performance graphene/silk fibroin based carbon (GCN-S) material for supercapacitors.

Both silk fibroin (SF) and cellulose are considered as potential substitutes of synthetic polymers because of the problems for the exhaustion of fossil resources and the pollution of environment. In order to obtain a material that exhibits both the advantages of SF and cellulose, ionic liquid (IL) was introduced to prepare blend films of SF and cellulose in the present work. We found that by our new fabricate method, i.e. coagulating SF/cellulose IL mixture solution by vapored methanol and cold pressing during vacuum dry, the resulted SF/cellulose blend films were transparent owing to the significant compatibility between cellulose and SF. The mechanical properties of the blend films in dry state is better than other reported counterparts, while those in wet state is good enough for further applications. Our results also confirms that the miscibility of SF and cellulose was induced by the intermolecular interactions between the components in the same blend system but with different fabricating methods in the literature. In addition, mouse fibroblast L929 cells was found to show the significant adhesion and proliferation on the blend film, which suggested that the treatment of IL and methanol may not affect the biocompatibility of SF/cellulose blend films.

As in other polymer blends, the phase behavior of silk fibroin (SF) blends with other polymers is thought to be important for their related properties. Here we used FTIR imaging to study the phase behavior of three silk protein-based polymer blends, silk fibroin/chitosan (SF/CS) blend, silk fibroin/sodium alginate (SF/SA) blend, and silk fibroin/polyvinyl alcohol (SF/PVA) blend. FTIR images of the films prepared from these polymer blends indicated that the SF/CS blend was compatible, the SF/SA blend was partially compatible, and the SF/PVA blend was incompatible. The results accord with the conclusions from the conventional analysis methods like SEM, DSC, and DTMA reported in the literature. Moreover, we show that FTIR images of the blends can provide additional useful information on the composition of the individual components, and the conformation of SF at defined locations with a spatial resolution of 4 μm. Therefore, we believe FTIR imaging is a useful technique to better understand both the chemical and physical properties of silk protein-based polymer blends, and other kinds of polymer blends.

The extraordinary comprehensive mechanical properties of animal silk (especially spider and silkworm silk) have led to extensive research on the underlying mechanisms involved. Herein, we selected various regenerated silk fibroin (RSF) fibers by choosing different postdraw conditions in a wet-spinning process developed in this laboratory to study their structure–property relationship. We use synchrotron radiation infrared and X-ray diffraction techniques to monitor the structural differences in these RSF fibers and correlate them with their mechanical properties. The results show that with the increase of post draw-down ratio, the β-sheet content, crystallinity, and molecular orientation in these RSF fibers increase while the crystalline size decreases. The relationship between structural changes and the draw-down ratio reflects the corresponding variation in mechanical properties, namely, an increase in breaking stress with a decline in breaking strain in relation to increases in draw-down ratio. Therefore, these results provide solid and direct evidence on the evolution of structure during the artificial spinning process and on how structure determines the final mechanical performance of silk fibers. We believe this study provides a good background on the relationship between microscopic structure and macroscopic properties in polymer science and may prove useful in the production of high performance materials, not only for silk fibers but also for other natural and synthetic polymeric materials.

The Bombyx mori silkworm is well known as it has been bred by our ancestors with mulberry tree leaves for thousands of years. However, Bombyx mori is not the only silkworm that can produce silk, many other kinds of silkworms can also make silks for commercial use. In this research, we compare the mechanical properties of five different commercial silk fibres including domesticated mulberry Bombyx mori, non-mulberry semi-domesticated eri Samia ricini, and wild tropical tasar Antheraea mylitta and muga Antheraea assamensis. The results demonstrate that the non-mulberry silk fibres have a relatively high extensibility as compared to the mulberry silk fibres. In the meantime, the non-mulberry silk fibres show comparatively unique toughness to the mulberry silk fibres. Synchrotron radiation FTIR microspectroscopy, synchrotron radiation wide angle X-ray diffraction, and Raman dichroism spectroscopy are used to analyze the structural differences among the five species of silk fibres comprehensively. The results clearly show that the mechanical properties of both mulberry and non-mulberry silk fibres are closely related to their structures, such as β-sheet content, crystallinity, and the molecular orientation along the fibre axis. This study aims to understand the differences in the structural and mechanical properties of different mulberry and non-mulberry silk fibres, which are of importance to the related research on understanding and utilizing the non-mulberry silk as a biomaterial. We believe these investigations not only provide insight into the biology of silk fibroins from the non-mulberry silkworms but also offer guidelines for further biomimetic investigations into the design and manufacture of artificial silk protein fibres with novel morphologies and associated material properties for future use in different fields like bioelectronics, biomaterials and biomedical devices.

Animal silks, especially spider dragline silks, have an excellent portfolio of mechanical properties, but it is still a challenge to obtain artificial silk fibers with similar properties to the natural ones. In this paper, we show how to extrude tough regenerated silk fibers by adding a small amount of commercially available functionalized multiwalled carbon nanotubes (less than 1%) through an environmentally friendly wet-spinning process reported by this laboratory previously. Most of the resulting regenerated silk fibers exhibited a breaking energy beyond 130 MJ m-3, which is comparable to spider dragline silks (∼160 MJ m-3). The best of these fibers in terms of performance show a breaking stress of 0.42 GPa, breaking strain of 59%, and breaking energy of 186 MJ m-3. In addition, we used several advanced characterization techniques, such as synchrotron radiation FTIR microspectroscopy and synchrotron radiation X-ray diffraction, to reveal the toughening mechanism in such a protein-inorganic hybrid system. We believe our attempt to produce such tough protein-based hybrid fibers by using cheap, abundant and sustainable regenerated silkworm protein and commercially available functionalized carbon nanotubes, with simplified industrial wet-spinning apparatus, may open up a practical way for the industrial production of super-tough fiber materials.

We present an injectable hydrogel based on silk fibroin (SF) nanofibrils which may offer benefits for cell encapsulation and delivery.

Considering the three-dimensional ordered network of Ni foam-supported catalysts and the toxicity effects of volatile organic compounds (VOCs), the design of proper active materials for the highly efficient elimination of VOCs is of vital importance in the environmental field. In this study, a series of Co-Mn composite oxides with different Co/Mn molar ratios grown on interconnected Ni foam are prepared as monolithic catalysts for total toluene oxidation, in which Co1.5Mn1.5O4 with a molar ratio of 1 : 1 achieves the highest catalytic activity with complete toluene oxidation at 270 °C. The Co-Mn monolithic catalysts are characterized by XRD, SEM, TEM, H2-TPR and XPS. It is observed that a moderate ratio of Mn/Co plays significant effects on the textural properties and catalytic activities. From the XPS and H2-TPR characterization results, the obtained Co1.5Mn1.5O4 (Co/Mn = 1/1) favors the excellent low-temperature reducibility, high concentration of surface Mn3+ and Co3+ species, and rich surface oxygen vacancies, resulting in superior oxidation performance due to the formation of a solid solution between the Co and Mn species. It is deduced that the existence of the synergistic effect between Co and Mn species results in a redox reaction: Co3+-Mn3+ ↔ Co2+-Mn4+, and enhances the catalytic activity for total toluene oxidation.

We designed an injectable hydrogel by dissolving MoS2/Bi2S3-PEG (MBP), doxorubicin (DOX) and agar into water for the concurrent tumor photothermal and chemotherapy. The formed solution was able to be intra-tumorally (I.T.) administered into tumor at a relatively high temperature and automatically formed a hydrogel after cooling to body temperature. The resultant Agar/MBP/DOX (AMD) hydrogel can act as a macro-vessel to retain the MBP nanosheet and DOX and restrict their access to body fluid circulation. Moreover, AMD hydrogel did not compromise the photoacoustic and computed tomography imaging capacity, as well as the photothermal and chemotherapy efficiency of MBP nanosheets and DOX. The heat from the photothermal transformation of MBP nanosheet can promote the drug-release from the hydrogel and thus enable an on-demand drug release. Furthermore, antibiotics were also able to be encapsulated in the hydrogel to avoid the potential wound infection during tumor surgery.

The effect of Ca modification on the Ni/ZSM-5 catalyst for efficient toluene oxidation was studied in a plasma-catalytic system. The Ni/ZSM-5 and Ca-Ni/ZSM-5 catalysts were prepared by a wet impregnation method and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Pyridine-FTIR spectroscopy and temperature programmed desorption of ammonia (NH3-TPD). Among the catalysts tested, the Ca-Ni/ZSM-5 sample showed the best potential for toluene conversion (90.2%) and CO2 selectivity (70.7%). Pyridine-FTIR spectra and NH3-TPD results proved that the introduction of Ca and Ni onto ZSM-5 caused a decrease in the strong and weak acidic sites. In addition, gas chromatography/mass spectrometry (GC-MS) result showed that the Ca-Ni/ZSM-5 catalyst reduced the production of undesirable byproducts (such as p-nitrotoluene and methyl benzoate). Calcium in the Ni/ZSM-5 system influenced the acidity and other surface characteristic of the catalyst, as well as directly impacting the reactive plasma species and the intermediates. Finally, possible reaction mechanisms in the plasma catalysis of toluene were also proposed.

Abstract The emergence of ionotronic materials has substantially extended the applications of artificial skins by allowing intimate interfaces between electronics and biological/bionic surfaces toward achieving improved sensing and communication with surrounding stimuli. However, ionotronic skins are intrinsically temperature dependent, since water molecules play crucial roles in regulating both mechanical and ionic conductivity of the materials. Hence, most of the ionotronic skins will fail at temperatures below 0 °C. In this study, a highly sensitive ionotronic skin that can be used in the entire natural environmental temperature range (−30–80 °C) is developed by using silk fibroin and Ca(II) ions as starting materials. In such a system, silk fibroin serves as both structural supports and ion capture agent to provide structural stability, mechanical flexibility, and interfacial adhesion ability, while Ca(II) ions work as ionic conductor, hygroscopic agent, and deicing salt to offer highly stable ionic conductivity at a temperature range from −30 to 80 °C. These synergetic merits, together with favorable advances of silk fibroin ionotronic skins in biocompatibility, transparency, and self‐healing, allow them to be used in multiple emerging fields, such as regenerative medicine, implantable electronics, and human–machine interface.

With developments in tissue engineering, artificial ligaments are expected to be future materials for anterior cruciate ligament (ACL) reconstruction. However, poor healing of the intraosseous part after ACL reconstruction significantly hinders their applications in this field. In this study, a bioactive clay Laponite (LAP) was introduced into the regenerated silk fibroin (RSF) spinning dope to produce functional RSF/LAP hybrid fibers by wet-spinning. These RSF/LAP hybrid fibers were then woven into artificial ligament for ACL reconstruction. The structure and mechanical properties of RSF/LAP hybrid fibers were extensively studied by different means. Results confirmed the presence of LAP in RSF fibers and revealed that the addition of LAP slightly deteriorated the comprehensive mechanical properties of RSF fibers. However, they were still much tougher (with higher breaking energy) than those of degummed natural silkworm silk that was earlier used for making artificial ligament. The artificial ligament woven from RSF/LAP hybrid fibers showed better cytocompatibility and osteogenic differentiation with mouse pre-osteoblasts in vitro than those made from degummed natural silkworm silks and pure RSF fibers. Furthermore, in vivo study in a rat ACL reconstruction model demonstrated that the presence of LAP in the artificial ligament could significantly enhance the graft osseointegration process and also improve the corresponding biomechanical properties of the artificial ligament. Based upon these results, the RSF/LAP hybrid fibers, which can be mass produced by wet-spinning process, are believed to have a great potential for use as artificial ligament materials for ACL reconstruction. In this study, we successfully introduced Laponite (LAP), a kind of clay that has the function of osteogenic induction, into regenerated silk fibroin (RSF) fibers, which was prepared by a mature wet-spinning method developed in our lab. We believe that through artificial spinning, additional functional components can be added into RSF fibers, which one can hardly achieve with natural silks. We showed that the artificial ligament woven from RSF/LAP hybrid fibers had better cytocompatibility and osteogenic differentiation for mouse pre-osteoblasts in vitro, and significantly enhanced the graft osseointegration process and improved the corresponding biomechanical properties in a rat ACL reconstruction model in vivo, compared to those artificial ligaments made from degummed natural silkworm silks and pure RSF fibers.

Protein-based adhesives have gained considerable interest, due to their unique ecofriendliness and abundant functional groups. However, the presence of polar groups results in poor water resistance and unsatisfactory bonding strength of protein-based adhesives, limiting their practical applications. In addition, the complicated preparation process also made the production of protein-based adhesives time-consuming and costly. In this work, a hydrophobic protein zein, which lacks polar groups, was chosen as a basic ingredient for the preparation of protein-based adhesive. Sodium dodecyl sulfate (SDS) with a concentration of 200 mmol/L was added to promote the dissolution of zein and also render it negatively charged. The cations in metal chloride solution effectively cross-linked with SDS modified zein molecular chains, resulting in the formation of final zein-based adhesives. Results showed that a zein-based adhesive formed after treatment with 5 wt % FeCl3 aqueous solution (Fe(III)@zein/SDS adhesive) showed the best performance. It indicates that Fe(III)@zein/SDS adhesive could bond a wide range of materials. Four common substrates were chosen to test the adhesive properties of Fe(III)@zein/SDS adhesive at 25 °C, including one inorganic material glass, one metal material copper, and two organic polymer materials polyvinyl chloride (PVC) and polyimide (PI). The adhesive strength of Fe(III)@zein/SDS adhesive was found from 125 kPa (PI) to 586 kPa (copper) in dry conditions, while from 12 kPa (copper) to 33 kPa (PI) in the wet state, displaying a promising adhesive strength in both dry and wet conditions. Meanwhile, the Fe(III)@zein/SDS adhesive can be easily removed from the attached surfaces without nonchemical contamination by immersing in 70% ethanol aqueous solution. Therefore, such an environmentally friendly protein-based adhesive has great potential for practical use in various fields.

Multi-responsive sensing devices have contributed extensively to health monitoring applications. However, the effects of different stimuli often confuse, and thus cause, signal distortion of the sensor response. In addition, many sensing devices cannot work properly at low temperatures. In the present study, a robust regenerated silk fibroin (RSF)-based hydrogel was fabricated with silver nanowires (AgNWs) embedded in the surface. The microstructure of AgNW-embedded RSF surface was introduced using cotton fabric as a template. Afterwards, the hydrogel was immersed in an aqueous calcium chloride solution to introduce Ca(II) ions into the matrix of the RSF hydrogel. Finally, two pieces of the RSF/AgNW/Ca(II) hydrogel were assembled with AgNW layer face-to-face to form a dual-responsive ionotronic skin that was sensitive to pressure and temperature. The pressure-response of the RSF/AgNW/Ca(II) ionotronic skin showed a high sensitivity, short response time, and good durability. In addition, the temperature-response also showed a high sensitivity and good durability from low temperatures (−30°C) to high temperatures (50°C). As a demonstration of its dual responsiveness, 16 pieces of RSF/AgNW/Ca(II) ionotronic skin were combined to make a 4 × 4 array. It demonstrated high sensitivity without interference between the pressure and temperature signals, achieving a significant dual response. A potential application for the simultaneous detection of body temperature and heartbeat was demonstrated by placing the RSF/AgNW/Ca(II) ionotronic skin on the wrist and further indicated the practicality of such an ionotronic skin because it could distinguish between the percussion wave, tidal wave, and diastolic wave in a single waveforms. Therefore, this RSF/AgNW/Ca(II) ionotronic skin that can discriminated between stimuli and work at low temperatures may have great potential in the field of wearable health monitoring equipment.

The development of reliable glucose sensors for noninvasive monitoring is highly desirable and essential for diabetes detection. As a testing sample, sweat is voluminous and is easy to collect compared to blood. However, the application of sweat glucose sensors is generally limited because of their low stability and sensitivity compared to commercial glucometers. In this manuscript, a silk nanofibril (SNF)/reduced graphene oxide (RGO)/glucose oxidase (GOx) composite was developed as the working electrode of the sweat glucose sensor. The SNF/RGO/GOx composite was prepared via a facile two-step process, which involved the self-assembly of SNF from silk fibroin while reducing graphene oxide to RGO and immobilizing GOx on SNF. The SNF/RGO/GOx glucose sensor exhibited a low limit of detection (300 nM) and high sensitivity (18.0 μA/mM) in the sweat glucose range, covering both healthy people and diabetic patients (0–100 μM). Moreover, the SNF/RGO/GOx glucose sensors showed a long stability for at least 4 weeks. Finally, the SNF/RGO/GOx glucose sensor was applied to test the actual sweat samples from two volunteers and two sweating methods (by dry sauna and exercise). The results indicate the glucose data tested by the SNF/RGO/GOx glucose sensor were reliable, which correlated well to the data obtained from the commercial glucometer. Therefore, the SNF/RGO/GOx glucose sensor developed in this study may have a great potential for glucose control in personalized healthcare monitoring and chronic disease management.

A novel natural polymer blend, namely, a semi-interpenetrating polymer network (semi-IPN) composed of crosslinked chitosan with glutaraldehyde and silk fibroin was prepared. The FTIR spectra of the semi-IPN manifested that the chitosan and silk fibroin had a strong hydrogen-bond interaction and formed an interpolymer complex. The semi-IPN showed good pH sensitivity and ion sensitivity. According to the different swelling ratios of the semi-IPN in the buffer solution with different pH values or the AlCl3 aqueous solution with different concentrations, the semi-IPN could swell and shrink while being put alternately into different pH buffer solutions or AlCl3 aqueous with different concentrations. The semi-IPN could also act as an “artificial muscle” because its swelling-shrinking behavior exhibited a fine reversibility. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2257–2262, 1997

The conformation of silk fibroin in silk fibroin/chitosan (SF/CS) blend membrane was analyzed by infrared spectrum, X-ray diffractometry, and Raman spectrum. The results demonstrated that the SF could show β-sheet conformation when the SF content in blend membranes was 10% (w/w) and 60–80% (w/w), while the pure SF membrane showed random coil conformation. A mechanism of the conformation transition was suggested in that the SF chain could use the rigid CS chain as a mold plate to stretch itself to form a β-sheet structure according to the strong hydrogen bond between CS and SF. Therefore, a new concept, named “Polymer-Induced Conformation Transition,” was proposed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2293–2296, 1997

We used time-resolved Fourier transform infrared spectroscopy (FTIR) to follow a conformation transition in Nephila spidroin film from random coil and/or helical structures to beta-sheet induced by the addition of KCl from 0.01 to 1.0 mol/L in D(2)O. Time series difference spectra showed parallel increases in absorption at 1620 and 1691 cm(-)(1), indicating formation of beta-sheet, together with a coincident loss of intensity of approximately 1650 cm(-)(1), indicating decrease of random coil and/or helical structures. Increase in KCl concentration produced an increased rate of the conformation transition that may attributable to weakening of hydrogen bonds within spidroin macromolecules. The conformation transition was a biphasic process with [KCl] > or = 0.3 mol/L but monophasic with [KCl] < or = 0.1 mol/L. This suggests that, at high KCl concentrations, segments of the molecular chain are adjusted first and then the whole molecule undergoes rearrangement. We discuss the possible significance of these findings to an understanding of the way that spiders spin silk.

A natural amphoteric polyelectrolyte hydrogel film was prepared by solution blending of chitosan and its derivative carboxymethylchitosan, and cross-linked with glutaraldehyde. Under electric stimulus such a hydrogel quickly bends toward one electrode, showing an electrical sensitive behavior. Because of its amphoteric nature, the hydrogel bends either toward anode (pH ≤ 7) or cathode (pH > 7), depending on the pH of the electrolyte solution. Besides pH value, other factors, such as ionic strength, electric field strength, thickness of the hydrogel and the amount of cross-linking agent also influence the electromechanical behavior of the hydrogels. Compared with chitosan/carboxymethylcellulose hydrogel, which we reported previously, chitosan/carboxymethylchitosan hydrogel exhibits better overall mechanical properties and electrical sensitivity, suggesting its great potential for microsensor and actuator applications, especially in the biomedical field.

A macroporous amphoteric membrane was successfully prepared by solution blending of a natural polymer chitosan (CS) and its derivative carboxymethylchitosan (CMCS). The adsorption of two model proteins (ovalbumin and lysozyme) with very different pI values on this CS/CMCS blend membrane was investigated in batch systems. The results showed that both proteins could be effectively adsorbed on the membrane, but the adsorption capacities were influenced by the pH, the initial protein concentration and the CMCS content in the membrane. Because of the amphoteric nature of the protein and the CS/CMCS membrane, the pH for the maximum adsorption of ovalbumin and lysozyme was different, which is the basis for the separation of these proteins from binary mixtures. As the CS/CMCS blend membrane also showed good desorption properties for those two proteins, both ovalbumin and lysozyme were successfully separated from binary mixtures by adjusting only the pH of the feed and the desorption solutions.

Protein adsorption-desorption on nanoscale surface plays a key role in biomaterials, cell adhesion, biosensors, biofuel cells and biomineralization. Silicate-substituted hydroxyapatite (SiHA) is one of the most interesting bioceramics in the field of bioactive hard tissue implants. In this paper, the adsorption-desorption behaviors of leucine-rich amelogenin protein (LRAP) on a series of SiHA (100) surfaces were investigated using the molecular dynamics (MD), steered molecular dynamics (SMD) simulations and density functional theory (DFT) calculations. It was found that the silicate ions on SiHA (100) surface cause a shield effect, which was composed of the charge repulsion and the steric hindrance of silicates. These findings suggest that surface engineering technologies can be potentially used to directly control/manufacture the nanoscale surface texture and the composition of material surfaces, thereby to mediate the interaction of proteins with biomaterials.

The changes of the secondary structure of silk proteins, including β-sheet, helical and random coil content during the conformation transition process have been widely studied with various methods by many researchers, however few reports relate to β-turn formation. In this paper, β-turn formation during the conformation transition in both regenerated silk fibroin (RSF) solutions and films was monitored by time-resolved FTIR spectroscopy. The results show that the kinetics of β-turn formation varies not only in RSF solution or film, but also depends on the concentration of ethanol used to induce the conformation transition. Our observations confirm that the absorption band around 1690 cm−1 is not the high frequency band of anti-parallel β-sheet, but represents β-turns possibly together with a component derived directly from β-sheet as proposed in our previous work. Our findings also suggest that the free adjustment of silk fibroin macromolecular chains is very important for the formation of regular β-sheet structure, essential for the strength of silk fibers, with important implications for the natural spinning mechanism of animal silks and attempts to copy this industrially.

An antimicrobial silver nanoparticles (AgNPs) embedded soy protein isolation (SPI) film was prepared by an easy and efficient blending method. AgNPs were in situ synthesized from SPI/AgNO3 solution, taking the advantage of the reducibility of tyrosine residue in SPI. The whole reaction process was carried out by exposure to the white light at ambient temperature, so such a synthesis method of AgNPs is highly energy-efficient and eco-friendly. The TEM and UV–vis spectroscopy observations indicated that the AgNPs were homogeneously distributed without obvious aggregation. The SPI/AgNPs films were prepared by blending in situ synthesized AgNPs in SPI solution and additional pristine SPI solution, which showed an effective antimicrobial activity against both Gram-positive and Gram-negative bacteria. In the film preparation process, SPI acts as the reducing agent of AgNO3, the stabilizing agent of AgNPs, and the matrix of SPI/AgNPs film simultaneously, avoiding using any other chemicals. Such a green route of the preparation ensures SPI/AgNPs film may have the great potential for the application in food industry and biomedical fields.

Mesocrystals with the symmetry defying morphologies and highly ordered superstructures composed of primary units are of particular interest, but the fabrication has proved extremely challenging. A novel strategy based on biomineralization approach for the synthesis of hematite mesocrystals is developed by using silk fibroin as a biotemplate. The resultant hematite mesocrystals are uniform, highly crystalline, and porous nanostructures with tunable size and morphologies by simply varying the concentration of the silk fibroin and iron(III) chloride in this biomineralization system. In particular, we demonstrate a complex mesoscale biomineralization process induced by the silk fibroin for the formation of hematite mesocrystals. This biomimetic strategy features precisely tunable, high efficiency, and low-cost and opens up an avenue to access new novel functional mesocrystals with hierarchical structures in various practical applications.

Soy protein based materials are of great interest because of the merits of biocompatibility, biodegradability, renewability, etc. However, the poor mechanical properties and high water sensitivity limit their further application in many fields. In this paper, we tried to overcome these shortcomings through a slight chemical modification of the polypeptide chains of soy protein. 31P NMR and solid state 13C CP/MAS NMR spectroscopy confirmed that the diethoxy phosphoryl groups were successfully grafted onto soy protein chains with a molar grafting ratio of 0.15–1.18%, which almost did not change the nature of soy protein. The isoelectric point and rheological behavior of the modified soy protein sample varied with the grafting ratio, indicating that the tertiary structure of the protein was changed after phosphoryl modification. The FTIR spectra of the modified soy protein suggested that the increase of β-sheet conformation from the slight chemical modification could be the reason for the change of the globular structure of soy protein. Finally, we obtained a robust soy protein film as expected, and we did not use any crosslinking agent and plasticizer that were almost unavoidable in the previous studies reported in the literature. The tensile strength and the elongation at break of our soy protein films were 35 ± 5 MPa, 2.5 ± 0.5% in the dry state, and 3.8 ± 1.5 MPa, 125 ± 5% in the wet state, respectively. We believe that the method we developed in this communication provides a practical approach to improve the mechanical properties and broaden the applications of natural soy protein based materials.

A novel nanosystem, Janus particle Dox-CMR-MS/Au-6MP with opposing mesoporous silica and gold faces is able to monitor intracellular dual-drug responsive release in real time based on fluorescence resonance energy transfer (FRET) and surface-enhanced Raman scattering (SERS).

A continuous polydiacetylene fibre based on a peptide amphiphile is developed to exhibit ultrafast, reversible thermochromism, and a general and effective model is discovered to quantitatively predict the critical temperature of the chromatic transition.

Owing to their promising applications in flexible electronics, researchers have extensively explored flexible and conductive gels. However, these gels have unsatisfactory strength and flexibility as well as easily dry in air. Herein, a rationally designed robust regenerated silk fibroin (RSF)-based gel with significant flexibility and strength, favorable conductivity, and excellent air stability is fabricated by inducing the conformation transition of RSF from random coil to β-sheet in ionic liquid (IL)/water mixtures. We found that such RSF-based gels have a unique homogeneous network structure of RSF nanofibers, which is likely formed because of evenly distributed cross-links dominated by small-sized β-sheet domains created during the conformation transition of RSF. Although the unique homogeneous nanostructure/network contributes toward improving the mechanical properties of these gels, it also provides pathways for ionic transport to help the gels preserve high conductivity of ILs. The prepared RSF-based gels display a remarkable air stability and reversible loss/absorption water capability in a wide humidity range environment primarily because of the distinguished combination of the IL and water. Therefore, the novel RSF-based gels hold a great potential in various applications as multifunctional, flexible, conductive materials, which are dispensed with encapsulation.

In this work, silica nanoparticles modified with a new N-halamine precursor (EBDMH-SiO2 NPs) were synthesized through immobilization of 3-(4′-epoxyethyl-benzyl)-5,5-dimethylhydantoin (EBDMH) on the surface of amino-functionalized silica NPs. Then, EBDMH-SiO2 NPs and poly(lactic acid) (PLA) were blended at 185 °C to prepare a novel environmentally friendly PLA based nanocomposite (PLA/EBDMH-SiO2). The addition of EBDMH-SiO2 NPs has great influences on the thermal properties of nanocomposite. DSC results show that the grass transition temperature (Tg), cold crystallization temperature (Tcc) and melting temperature (Tm) of PLA in nanocomposites gradually decrease with the increase of EBDMH-SiO2 NPs contents up to 5%. After that, further rise in EBDMH-SiO2 NPs content actually increases Tg, Tcc, and Tm. The overall crystallization and spherulite growth rate of PLA show the similar trend. Furthermore, the introduction of EBDMH-SiO2 NPs increases the storage modulus and viscosity of the melt of nanocomposite, providing an additional benefit for PLA blowing and injection molding. After chlorination, the N-halamine precursors on the nanocomposite surfaces are transformed into N-halamines, which provide strong antibacterial activities against E. coli (CMCC 44103) and S. aureus (ATCC 6538), pointing to good potentials of the PLA/EBDMH-SiO2 nanocomposites for antibacterial applications including food packaging, filters, and a wide range of hygienic products.

LAPONITE® (LAP) nanoplatelets were incorporated within a regenerated silk fibroin (RSF) microfibrous mat <italic>via</italic> electrospinning, which exhibited better cell adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) than the pristine RSF ones.

Recovering light alkanes from natural gas is a critical but challenging process in petrochemical production. Herein, we propose a postmodification strategy via simultaneous metal/ligand exchange to prepare multivariate metal–organic frameworks with enhanced capacity and selectivity of ethane (C2H6) and propane (C3H8) for their recovery from natural gas with methane (CH4) as the primary component. By utilizing the Kuratowski-type secondary building unit of CFA-1 as a scaffold, namely, {Zn5(OAc)4}6+, the Zn2+ metal ions and OAc– ligands were simultaneously exchanged by other transition metal ions and halogen ligands under mild conditions. Inspiringly, this postmodification treatment can give rise to improved capacity for C2H6 and C3H8 without a noticeable increase in CH4 uptake, and consequently, it resulted in significantly enhanced selectivity toward C2H6/CH4 and C3H8/CH4. In particular, by adjusting the species and amount of the modulator, the optimal sample CFA-1-NiCl2-2.3 demonstrated the maximum capacities of C2H6 (5.00 mmol/g) and C3H8 (8.59 mmol/g), increased by 29 and 32% compared to that of CFA-1. Moreover, this compound exhibited excellent separation performance toward C2H6/CH4 and C3H8/CH4, with high uptake ratios of 6.9 and 11.9 at 298 K and 1 bar, respectively, superior to the performance of a majority of the reported MOFs. Molecular simulations were applied to unravel the improved separation mechanism of CFA-1-NiCl2-2.3 toward C2H6/CH4 and C3H8/CH4. Furthermore, remarkable thermal/chemical robustness, moderate isosteric heat, and fully reproducible breakthrough experiments were confirmed on CFA-1-NiCl2-2.3, indicating its great potential for light alkane recovery from natural gas.

Abstract Organic ultrathin nanofilms are increasingly favored in a wide range of applications, including flexible photonics and electronics, smart skin devices, sensing, and bioinspired designs, due to their high flexibility, chemical activity, and stimuli‐responsiveness. To create large‐area, robust, and freestanding nanofilms efficiently, a protein interfacial cooperative assembly technique that utilizes silk fibroin and lysozyme as building blocks is developed. The strong intermolecular interaction between these two proteins, coupled with the abundant intra‐ and intermolecular β‐sheets, confers remarkable mechanical robustness to the nanofilms with thicknesses as low as 50 nm. Consequently, these nanofilms exhibit the unique ability to stand freely in the air and can be conformally transferred to substrates of different types and topographies, forming stable, and versatile nanocoatings. The advantageous attributes of their ultrathinness, large‐scale homogeneity, robustness, and rapid and tunable responsiveness facilitate the construction of ultrasensitive photonic architectures and organic–inorganic hybrid multilayers with outstanding optical and mechanical properties. It is envisioned that these all‐protein‐based robust nanofilms with unique nanoscale effects can be easily integrated into various advanced technological platforms to enable adaptive, multifunctional, and intelligent systems with exceptional mechanical strength.

This paper summarizes recent work in our groups on the factors that influence the formation of spider silks during the spinning process. The review encompasses: (a) extrusion variables that greatly affect the mechanical properties of the silk filaments; such as rate and temperature at spinning as well as the post-drawn treatment and (b) other factors affecting the conformation transition of the spider silk proteins (spidroin) such as pH and metallic ions. The observations taken together imply that the spinning process is at least as central as, and probably more important than, the composition of the ‘raw’ protein spinning solution. This conclusion leads us to suggest that in the future high-performance, artificial ‘spider’ silks may be spun from a range of solutions of silk and synthetic proteins.

Abstract The adsorption of lysozyme was investigated with novel macroporous chitosan (CS)/carboxymethylcellulose (CMC) blend membranes. The CS/CMG blend membranes were prepared by a simple solution‐blending method with glutaraldehyde as a crosslinking agent for CS and with silica particles as porogens. The CS/CMC blend membranes were insoluble in aqueous media when the CMC concentration in the membranes did not exceed 30 mol %. The protein adsorption on these membranes from aqueous solutions containing different amounts of lysozyme at different pHs was investigated in batch systems. The results showed that the lysozyme adsorption capacity had a maximum at pH 9.2, and this indicated that the CS/CMC blend membranes could act as cation‐exchange membranes. Moreover, the blend membranes showed the best adsorption properties for lysozyme when the CMC concentration was 20 mol %. In addition, the lysozyme adsorption capacity of the blend membranes increased with an increase in the initial lysozyme concentration and the adsorption temperature. The maximum adsorption capacity of the macroporous CS/CMC blend membranes was as high as 240 mg/g (170 mg/mL), and more than 95% of the adsorbed lysozyme was desorbed in a pH buffer at 11.8. The blend membranes also demonstrated good reusability after several adsorption–desorption cycles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1267–1274, 2005

Near-infrared spectroscopy (NIR) and differential scanning calorimetry (DSC) were used to investigate temperature-induced changes in the secondary structure and hydration of reconstituted Bombyx mori silk fibroin, with and without freezing water, by looking at regenerated silk fibroin films with a range of water content. We suggest that freezing water facilitates the movement of peptide chains and thus contributes to the conformational transition at 60 °C. The structural changes during heat treatment were analyzed by the two-dimensional correlation method. It was found that the band at 4600 cm−1 consists of complex overlapping components due to different secondary structure elements which compose the protein architecture. Thus, this band could be used as a sensitive probe to estimate the conformations of silk fibroin. By monitoring the variations of the spectral components dynamically, an NIR procedure for tracking the conformational transition of silk fibroin was established.

In this paper, a novel thixotropic injectable hydrogel has been developed by blending regenerated silk fibroin (SF) and hydroxypropylcellulose (HPC). Dynamic oscillatory rheology showed that the blends gelled at 37 °C within 1 h, and the gelation kinetics and gel properties were controllable by tuning the mix ratio of the blends. The gelation mechanism of such blends was elucidated from morphological observations by confocal laser scanning microscopy (CLSM), structural characterization and a molecular mobility study viaRaman spectroscopy and quantitative 13C-NMR spectroscopy, respectively. The results suggested that the phase separation of the blends triggered the conformational transition of SF from random coil to β-sheet, and thus resulted in the gel network formation through the β-sheet crosslinks and the immobilization of the molecular chain in the dispersed phase. Moreover, it was demonstrated that the blend hydrogel could protect encapsulated cells against high shear force during injection, suggesting that the SF–HPC hydrogel is a promising vehicle for cell delivery. This injectable hydrogel with thixotropic rheological properties was expected to potentially overcome the problem of leakage of liquid precursors to neighboring tissues associated with the in situ formation of injectable hydrogels.

A natural electroactive protein hydrogel was prepared from soy protein isolate (SPI) solution by cross-linking with epichlorohydrin. Under electrical stimulus, such SPI hydrogel quickly bends toward one electrode, showing a good electroactivity. Because of its amphoteric nature, the SPI hydrogel bends either toward the anode (pH < 6) or cathode (pH > 6), depending on the pH of the electrolyte solution. Other factors, such as electric field strength, ionic strength and gel thickness also influence the electromechanical behavior of the SPI hydrogels. Moreover, this SPI hydrogel exhibits a good electroactive behavior under strong acidic (pH = 2 - 3) or basic (pH = 11 - 12) solutions, which is a significant improvement over two other kinds of natural electroactive hydrogels, i.e., chitosan/carboxymethylcellulose and chitosan/carboxymethylchitosan hydrogel, which we reported previously. The wide pH range and good electroactivity of this natural protein hydrogel suggests its great potential for microsensor and actuator applications, especially in the biomedical field, and also to increase the scope of natural polymer-based electroactive hydrogels.

An octapeptide, GAGAGAGY, was obtained by a novel method, i.e. hydrolysing Bombyx mori silk fibroin. Afterward, a dodecanoic acid–peptide conjugation was synthesized. This amphiphile assembled into cylindrical nanofibers of planar β-sheets at pH 9 and twisted β-sheets at pH 4.

A green, simple and economical route based on an efficient Bombyx mori silk fibroin assisted hydrothermal process has been developed to synthesize monodisperse hematite (α-Fe2O3) nanostructures with fine shape control. The effects of reaction time and silk fibroin concentration on the morphology of α-Fe2O3 have been investigated systematically. Several morphologies including quasi-nanocubes, nanospheres that are composed of primary nanoparticles, and the coexistence of nanospheres and primary nanoparticles were obtained by varying the silk fibroin concentration. The formation mechanism of different α-Fe2O3 morphologies are discussed based on the silk fibroin template effect. In addition, these α-Fe2O3 nanostructures exhibit interesting shape-dependent magnetic properties. We believe that such a synthesis method of α-Fe2O3 provides an efficient shape control and cost-effective approach that is potentially competitive for scaling-up industrial production.

A clinical used anti-cancer drug floxuridine was successfully encapsulated in silk fibroin nanospheres. Such drug-loaded nanospheres have controllable size, fair drug-loading capacity and controlled release property, which maybe a good candidate for lymphatic chemotherapy.

The regenerated silk fibroin microhydrogel with thixotropic property could be bioprinted and then ripened to a tough hydrogel because of the change in “the second network” of the microhydrogel.

In this work, a new N-halamine precursor with two epoxy groups, 1,3-bis(2,3-epoxypropyl)-s-triazine-2,4,6-trione (BETT), was synthesized and used to enhance the compatibility between poly(lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT). The rheological analysis and GPC indicated that chain extension between PLA and PBAT occurred during the melt-blending in the presence of BETT. The PLA/PBAT chain extensions improved the compatibility between PLA and PBAT and hindered the crystallization of PLA. SEM images showed that PLA/PBAT blend gradually changed from the typical sea-island phase without BETT to a co-continuous structure with increase in amount of BETT. This showed that the interfacial compatibility between PLA and PBAT improved significantly on addition of BETT. Moreover, compared to PLA/PBAT blend, the mechanical properties of PLA/PBAT/BETT blends showed great improvement. Furthermore, the chlorinated PLA/PBAT/BETT sheets displayed excellent antibacterial activities against E. coli (CMCC 44103) and S. aureus (ATCC 6538) cultures, wherein the sheets with 17.5 ± 0.8 μg/cm2 of the active chlorine could kill all inoculated bacteria within 30 min.

Adsorption-discharge plasma system has been applied for catalytic removal of low concentration toluene over a series of Ni-SBA catalysts. Catalytic activity was evaluated towards different relative humidities of air (RH). Meanwhile, gas phase and catalyst surface by-products were investigated during oxidative decomposition of toluene using in situ Time of Flight-Mass spectrometry (TOF-MS), in situ Fourier Transform infrared spectroscopy (FT-IR) and GC–MS analysis technology. The results showed that 5% Ni-SBA sample exhibited higher toluene mineralization rate (71.8%) than that of other samples after 60 min plasma catalysis, and different RH (20–80%) had a negative impact on toluene degradation due to the competitive adsorption and the blocking of active sites on the catalysts surfaces. Interestingly, humidity decreased the yield of CO and increased in the production of CO2 due to the enhanced oxidation of both CO and other intermediates during the reaction. In situ TOF-MS spectra showed that several benzene series were detected in 5% Ni-SBA system during plasma catalysis, and suggested that Ni-SBA catalyst facilitated the benzyl oxidation but are not conducive to benzoic acid ring-opening reactions. In situ FT-IR analysis displayed many products that formed in the surface of Ni-SBA catalyst was degraded after 60 min plasma catalysis. Meanwhile, GC–MS result indicated that no nitrogen-containing byproducts were detected in the surface of Ni-SBA catalyst after 60 min plasma catalysis under 40% RH water vapor. The result may provide new insights for plasma catalysis removal of industrial VOCs at medium and high RH.

The separation of C2H6 and C3H8 from CH4 is extremely important in the petrochemical industry, but the separation technology is dominated by an energy-intensive and cost-intensive process of cryogenic distillation. With lower energy consumption and cost investment, adsorptive separation technology shows great potential for the purification of natural gas. Here, we prepared a Ni-based metal-organic framework CTGU-15 and investigated its performance for the separation of light alkanes. Results show that CTGU-15 has super-high C3H8 uptake (12.13 mmol/g) and relatively low CH4 uptake (0.40 mmol/g) at 298 K and 100 kPa. The reason why CTGU-15 shows super-high C3H8 uptake was studied by comparing the pore textural properties of CTGU-15 and other benchmark adsorbents. Additionally, computational simulations were used to explore the nature of the interaction of the C3H8 gas within CTGU-15. The adsorption selectivities of C3H8/CH4 and C2H6/CH4 on CTGU-15 are 170.7 and 5.2, respectively. Breakthrough experiments show that CTGU-15 can achieve the adsorptive separation of CH4/C2H6/C3H8 mixtures. Importantly, CTGU-15 can maintain the stability of the framework after the heat treatment at <770 K, five adsorption-desorption cycles and exposure to 58% RH for 3 days. This work indicates that CTGU-15 is a promising adsorbent for CH4/C2H6/C3H8 separation.

The co-delivery of multiple drugs using one drug carrier is a viable strategy to optimize drug dosage and reduce the side effects in chemotherapy. Herein, a hydrophilic animal protein (silk fibroin) and a hydrophobic plant protein (zein) were selected for preparing a composite drug carrier. Adapting our previously developed method for the preparation of regenerated silk fibroin (RSF) nanospheres, we prepared RSF/zein nanospheres that displayed an interesting structure including a single central hole. The particle size of the RSF/zein nanospheres was regulated from 150 to 460 nm by varying the preparation conditions, implying that such a drug carrier is suitable for both intravenous administration and lymphatic chemotherapy. Two anti-cancer drugs with different target sites, paclitaxel (PTX) and curcumin (CUR), were selected for the preparation of dual-drug-loaded CUR/PTX@RSF/zein nanospheres. Both drugs achieved a high loading capacity in the RSF/zein nanospheres, i.e., 8.2% for PTX and 12.1% for CUR. Subsequently, the encapsulated PTX and CUR were released from the RSF/zein nanospheres in a sustained manner for at least 7 days. Importantly, these dual-drug-loaded RSF/zein nanospheres exhibited a considerable synergistic therapeutic effect, showing more efficient suppression of in vitro cancer cell growth than free PTX or CUR, a combination of free PTX and CUR, or single-drug-loaded nanospheres. Therefore, the CUR/PTX@RSF/zein nanospheres developed in this study hold great potential for combination chemotherapy in future clinical applications.

Hydrogels are considered to be ideal biomedical materials as their physical properties are similar to the physiological tissue environment. In particular, thixotropic hydrogels have received increasing attention from researchers because of their injectability. Herein, a simple and rapid method was developed for the preparation of a regenerated silk fibroin (RSF) hydrogel with long-lasting and excellent thixotropy. The thixotropic RSF hydrogel was readily formed by ultrasonic treatment of the pretreated RSF solution for 2 min followed by incubation at 40 °C for 10 min. The storage modulus of the RSF hydrogels recovered to more than 90% of the original value within 20 s after withstanding 1000% shear strain. By avoiding complicated chemical or physical treatments and by addition of crosslinking agents and/or other chemical components, the obtained RSF hydrogels maintained excellent biocompatibility. Hence, the cells implanted inside the hydrogel can grow and proliferate normally. By virtue of ultrasonic treatment during the preparation, functional nanoparticles can be uniformly dispersed in the RSF solution to prepare RSF-based hybrid hydrogels with various functions. As an application example, hydroxyapatite (HAP) with osteoinductivity was mixed with RSF solution to prepare the RSF/HAP hybrid hydrogel. The RSF/HAP hybrid hydrogel maintained biocompatibility and thixotropy of the original RSF hydrogel and promoted osteoblastic differentiation of cells owing to the addition of HAP. Therefore, the RSF hydrogel prepared in this work has a strong application prospect in the biomedical field including, but not limited to, bone repair.

Evidence is presented here that cupric ions play a part in the natural spinning of Bombyx mori silk. Proton induced X-ray emission studies revealed that the copper content increased from the posterior part to the anterior part of silk gland, and then further increased in the silk fiber. Spectrophotometric analysis demonstrated that cupric ions formed coordination complexes with silk fibroin chains while Raman spectroscopy indicated that they induced a conformation transition from random coil/helix to beta-sheet. Taken together these findings indicate that copper could play a role in the natural spinning process in silkworms.

Abstract We used silica particles as a porogen to prepare macroporous chitosan membranes and subsequently prepared macroporous chitosan/Cu(II) affinity membranes for urea adsorption. The morphology, porosity, Cu(II) adsorption capacity, and swelling ratio of the macroporous membrane were measured. SEM photographs show the pores in the membrane dispersed uniformly, a feature that didn't change much after the adsorption of Cu(II). The porosity of the membrane had a maximum value when the silica/chitosan ratio was about 12. The Cu(II) adsorption capacity in the membrane leveled off when the initial concentration of CuSO 4 solution exceeded 5 × 10 −2 mol/L. The macroporous chitosan/Cu(II) affinity membrane was successfully used for urea adsorption. The maximum urea adsorption capacity was 78.8 mg/g membrane, which indicates that the membrane has a great potential for hemodialysis for urea removal. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1108–1112, 2003

Spider dragline silk with its superlative tensile properties provides an ideal system to study the relationship between morphology and mechanical properties of a structural protein. Accordingly, we synthesized two hybrid multiblock copolymers by condensing poly(alanine) [(Ala)5] blocks of the structural proteins (spidroin MaSp1 and MaSp2) of spider dragline silk with different oligomers of isoprene (2200 and 5000 Da) having reactive end groups. The synthetic multiblock polymer displayed similar secondary structure to that of natural spidroin, the peptide segment forming a β-sheet structure. These multiblock polymers showed a significant solubility in the component solvents. Moreover, the copolymer which contains the short polyisoprene segment would aggregate into a micellar-like structure, as observed by TEM.

The formation mechanism of RSF alcogel was elucidated from morphological observations using TEM, AFM and confocal laser scanning microscopy (CLSM) as well as the kinetic studies by Thioflavin T fluorescence and rheological methods. An intriguing dual-structure—a nanofibrillar network on the nanoscale and a floc-like network on the microscale—was observed within the RSF alcogel. Based on our kinetic study, the fractal dimension of the ramified fibrillar aggregate was found to be 2.4–2.8 depending on RSF concentration. Meanwhile, through a scaling analysis of the mechanical properties of RSF alcogels, the fractal dimension of the floc-linked network was found to be 2.2. Furthermore, our results showed that fibrillarization of RSF was triggered by a dramatic change in the interaction between RSF and cosolvent, and the gelation kinetics could be tuned by adjusting the concentration of ethanol as well as RSF. The controllable dual-structure and kinetics make such biopolymer gel a potential candidate for applications in nanotechnology.

An all-silk composite, in which uniaxially-aligned and continuous-typed Bombyx mori silk fibers were embedded in a matrix of silk protein (fibroin), was successfully prepared via a solution casting process. The structure, morphology, mechanical and thermal properties of such silk fiber/fibroin composites were investigated with X-ray diffraction, scanning electron microscopy, tensile and compression tests, dynamic mechanical analysis and thermogravimetric analysis. The results demonstrated that the interface adhesion between silk fiber and the fibroin matrix was enhanced by controlling the fiber dissolution through 6 mol L−1 LiBr aqueous solution. Compare to those of the pure fibroin counterparts, the overall mechanical properties as well as the thermal stability of such silk fiber/fibroin composites were significantly improved. For example, the composite with 25 wt% fibers showed a breaking stress of 151 MPa and a breaking elongation of 27.1% in the direction parallel to the fiber array, and a compression modulus of 1.1 GPa in the perpendicular direction. The pure fibroin matrix (film), on the other hand, typically had a breaking stress of 60 MPa, a breaking elongation of 2.1% and a compression modulus of 0.5 GPa, respectively. This work suggests that such a controllable technique may help in the preparation of animal silk based materials with promising properties for various applications.

Time-evolved gelation behavior of a chitosan-β-glycerophosphate (CS/β-GP) system was elucidated from rheological investigation, NMR analysis, fluorescence measurement, and morphology observation. Urea and isobutanol were selected to assess the interactions between the two components during the gelation process of the CS/β-GP system. Urea was found to be detrimental to the gelation process by both disrupting hydrogen bonding and retarding the formation of hydrophobic domains. On the contrary, the addition of isobutanol accelerated the sol–gel transition by strengthening the hydrophobic interactions. These results reveal that both hydrogen bonding and hydrophobic interactions within chitosan or between chitosan and β-glycerophosphate molecules are the main reasons for gel formation. The results also indicate that firstly the formation of hydrogen bonds makes the hydrophobic sites more accessible, and then the synergistic hydrogen bonding and hydrophobic interactions lead to the final formation of CS/β-GP gel network. This work demonstrates the possibility of tuning the gelling ability as well as the mechanical properties of CS/β-GP hydrogels. Thus, it gives the opportunities to optimize the performance of this promising natural thermosensitive material for practical applications in the future.

Three-dimensional (3D) copper oxide (CuO) nanostructures were synthesized in a regenerated Bombyx mori silk fibroin aqueous solution at room temperature. In the synthesis process, silk fibroin served as the template and helped to form the hierarchical CuO nanostructures by self-assembly. Cu(OH)2 nanowires were formed initially, and then they transformed into almond-like CuO nanostructures with branched edges and a compact middle. The size of the final CuO nanostructures can be tuned by varying the concentration of silk fibroin in the reaction system. A possible mechanism has been proposed based on various characterization techniques, such as scanning and transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. The synthesized CuO nanostructured material has been evaluated as an anode material for lithium ion batteries, and the result showed that they had a good electrochemical performance. The straightforward energy-saving method developed in this research may provide a useful preparation strategy for other functional inorganic materials through an environmentally friendly process.

The crystallization of calcium carbonate (CaCO3) was investigated using a mineralization system composed of a chitosan membrane and regenerated silk fibroin (RSF). Such a system may resemble the mineralization in molluscs, where chitosan is a derivative of chitin and RSF an analogue of nacreous protein. It was found that the vaterite disks generally formed on the chitosan membrane while the aragonite disks also appeared with changes of pH value or temperature of the solution. The crystallization of CaCO3 in the vicinity of the chitosan membrane was much more affected by the environment of crystallization, compared to that in bulk solution. Detailed observation from high-resolution scanning and transmission electron microscopy (HRSEM and TEM) showed that these disks consisted of nanoparticles about 20 nm in size, thus suggesting that the accumulation of hybrid CaCO3/RSF nanoparticles induced the formation of crystalline disks on the chitosan membrane.