Ultrasound and photoacoustic imaging to monitor mesenchymal stem cells labeled with gold nanoparticles

Mesenchymal stem cells (MSCs) are versatile in many tissue engineering applications and have the potential to be used for cellular therapies because they can differentiate into many cell types. Specifically, the use of MSCs for the treatment of ischemic disease is promising because MSCs can express characteristics of vascular cells. MSCs can promote vascular growth at the site of injury after delivery using a PEGylated fibrin gel. In order to quantitatively assess in vivo delivery and differentiation of MSCs, a non-invasive and high-resolution imaging technique is required. In this study, the combined ultrasound and photoacoustic imaging was demonstrated to monitor MSCs labeled with citrate-stabilized gold nanoparticles (Au NPs). It was observed that uptake of nanoparticles did not have a significant effect on cell viability and proliferation over a two-week period. Four different cell concentrations of either the non-labeled MSCs or the Au NP labeled MSCs were embedded in the tissue mimicking gelatin phantom. The ultrasound and photoacoustic signals were acquired and quantitatively analyzed to assess sensitivity and accuracy of the developed imaging approach. Furthermore, based on the results, the feasibility of in vivo ultrasound and photoacoustic imaging of MSCs was discussed.