Silica Nanoparticles For Mesenchymal Stem Cells Proliferation, Differentiation And In Vivo Tracking

Stem cells are characterized by the ability to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types. Recently, the wide spectrum of nanotechnologies holds great promise toward the study of stem cell biology and the development of new approaches to stem cell research. By combining the two important research fields of nanotechnology and stem cells research, the stem cells nanotechnology has been well developed and become a new intercross interdisciplinary field. Silica nanoparticles (SiNPs) are of interest for their biocompatibility and their mechanical properties. Because of their unique characteristics, SiNPs have been widely studied in a range of areas including chemistry, engineering and biomedicine, especially the application of functionalized SiNPs for cancer diagnostics and therapy. The nanoparticle's good biocompatibility and easy modification make them well-suited for a variety of biomedical studies, which provides a new route for stem cells research. Aiming at the direction of nanomaterials based carriers, the biocompatible silica nanoparticles (SiNPs) based carriers for Rat mesenchymal stem cells (RMSCs) proliferation, differentiation and in vivo tracking have been reported. The three parts of the thesis are as follows.1. Bioeffects of silica nanoparticles on mesenchymal stem cells proliferation and differentiationThe cell viability assay of RMSCs in the presence of pure SiNPs was first performed using MTT assay and morphology test. The results indicated the addition of SiNPs to the cell culture medium with last concentration of 0.05 mg/mL and 0.1 mg/mL did not affect the metabolic activity and the proliferation of RMSCs. As the concentration of SiNPs increased, the cell survival rate decreased. If the last concentration of SiNPs was not higher than 0.1 mg/mL, the survival rate of the cells after exposure for 24 h still kept around 80%. the pure SiNPs with concentration of creating little cytotoxicity had no effect on the on cellular ultrastructures, adipogenic differentiation and osteogenic differentiation. Similarly, TEM analyses of RMSCs results indicated that the the structures of treated RMSCs were preserved by compared with the control group without treatment of SiNPs and stayed in a relatively active period with normal cell function.2. Silica nanoparticles as biocompatibile carriers of insulin for mesenchymal stem cells adipogenic differentiation In the present study, the SiNPs based carriers of insulin for RMSCs adipogenic differentiation have been reported. SiNPs were then selected as carriers to be conjugated with insulin, one of important growth factor supplements for RMSCs adipogenic differentiation. In vitro cell studies were carried out in order to evaluate adipogenic efficacy of adipogenic induction media containing SiNPs-insulin conjugates through the control experiments. The results showed that the biological activity of insulin conjugated to the SiNPs was not affected and the SiNPs-insulin conjugates could be used for RMSCs adipogenic differentiation, which would help to expand the new potential application of SiNPs in stem cell research.3. Fluorescent nanoparticles for stem cell labeling and stem cell in vivo trackingThe feasibility of cellular labeling and tracking in vivo of Rubpy silica nanoparticles (FSiNPs) in the RMSCs have been studyed based on the the front work of tumor labeling and tracking. FSiNPs in the cells were assessed by flow cytometry and the result showed that 1000μg/mL of FSiNPs could enter RMSCs efficiently after 30 min incubation.The FSiNPs labeled stem cells were firstly injected into the neck of null mice subcutaneously. There was fluorescence of FSiNPs for 24 h by using an optical in vivo imaging system. The labeled stem cells were further injected into the tail veins of null mice and the tissue distribution of these labeled cells in nude mice were examined with fluorescence microscope. The result showed that characteristic fluorescence of FSiNPs was observed in the liver, the lung and the spleen, which primarily presumed the migration of stem cells. The challenge should be how to improve the internalizing efficiency of FSiNPs in the stem cells.