The use of nanoparticle labeling in cellular tracking

Abstract

Adult stem cells (ASCs) are a population of multipotent cells which have ability of self-renewal and tissue regeneration. Due to their protective and restorative roles, ASCs become candidate for cellular therapies. Some cellular imaging methods have been developed to monitor stem cell differentiation and migration. Regrettably, none of these techniques possess the properties of an ideal imaging methods such as photostability and non-toxicity. A new type of probe, conjugated polymer based water-dispersible nanoparticles (CPN) that possess strong fluorescence light emission, non-toxicity, photosability and high brightness, has been developed to fulfill the needs of cellular tracking. The aim of this study is to show the utilization of CPN labeling in in vitro and in vivo cellular tracking. We initially focused on the monitoring of the differentiation and migration of MSCs which have been proved to be a promising therapeutic tool. First we showed 24h CPN labeling did not cause severe decrease in the cellular activity of MSCs and had no effect on their marker expression and differentiation capacity in vitro. In addition, 24h CPN labeled MSCs showed very intense green fluorescence emission which was still bright after 3 weeks of MSC differentiation. We also showed CPN labeled MSCs were able to migrate to the damaged site and retained their labels in vivo. Similar to MSCs, DPSCs were labeled intensely and with negligible decrease in their cellular activity within 24h CPN incubation and it had no effect on their differentiation capacity. iv In addition, cancer cell tracking is important for the understanding of steps of metastasis and chemotherapeutic drug’s mode of action. Therefore, we tested CPN labeling in Huh7 cells, and we showed that labeled cells had very intense fluorescence emission without any change in their cellular activity. Moreover, tumor xenograft model that were generated with either 24h or 72h CPN labeled Huh7 cells showed that CPN labeling retained for about 2-3 months in vivo and did not lose their brightness. To conclude, we aim to propose a new approach for in vivo cellular tracking in order to obtain unattainable information of the migration and homing behaviors of the stem cells. In addition, our approach can also be used for evaluation of cancer cell metastasis as well as the success of stem cell or anti-cancer therapy.