Nanoparticles and their effects on differentiation of mesenchymal stem cells

Over the past decades, advancements in nanoscience and nanotechnology have resulted in numerous nanomedicine platforms. Various nanoparticles, which exhibit many unique properties, play increasingly important roles in the field of biomedicine to realize the potential of nanomedicine. Due to the capacity of self-renewal and multilineage mesenchymal differentiation, mesenchymal stem cells (MSCs) have been widely used in the area of regenerative medicine and in clinical applications due to their potential to differentiate into various lineages. There are several factors that impact the differentiation of MSCs into different lineages. Many types of biomaterials such as polymers, ceramics, and metals are commonly applied in tissue engineering and regenerative therapies, and they are continuously refined over time. In recent years, along with the rapid development of nanotechnology and nanomedicine, nanoparticles have been playing more and more important roles in the fields of biomedicine and bioengineering. The combined use of nanoparticles and MSCs in biomedicine requires greater knowledge of the effects of nanoparticles on MSCs. This review focuses on the effects of four inorganic or metallic nanoparticles (hydroxyapatite, silica, silver, and calcium carbonate), which are widely used as biomaterials, on the osteogenic and adipogenic differentiation of MSCs. In this review, the cytotoxicity of these four nanoparticles, their effects on osteogenic/adipogenic differentiation of MSCs and the signalling pathways or transcription factors involved are summarized. In addition, the chemical composition, size, shape, surface area, surface charge and surface chemistry of nanoparticles, have been reported to impact cellular behaviours. In this review, we particularly emphasize the influence of their size on cellular responses. We envision our review will provide a theoretical basis for the combined application of MSCs and nanoparticles in biomedicine.