Injectable inorganic/organic composite systems consisting of well-defined mesocrystals (4–8 μm) of calcium phosphate and polypeptide thermogel significantly enhance the osteogenic differentiation of the tonsil derived mesenchymal stem cells (TMSCs). Compared to composite systems incorporating nanoparticles (10–100 nm) or pure hydrogel systems, osteogenic biomarkers including alkaline phosphatase (ALP), bone morphogenetic protein 2, and osteocalcin are highly expressed at both the mRNA level and the protein level in the mesocrystal composite systems. ALP activity of differentiated cells is also significantly higher in the mesocomposite systems compared to the nanocomposite systems or the pure hydrogel systems. The mesocomposite systems provide not only hard surfaces for binding the cells/proteins by the inorganic mesocrystals but also a soft matrix for holding the cells by the hydrogel. Through the current research, (1) a novel method of preparing mesocrystals is developed, (2) TMSCs are proved as a new resource of stem cells, and (3) the mesocomposite systems are proved to be a promising tool in controlling stem cell differentiation. (4) Finally, the research emphasizes the significance of mesoscience as a new perspective of science in controlling cell and material interfaces.
Calcium phosphate mesocrystals and polypeptide thermogel composite systems provide an effective 3D scaffold for osteogenic differentiation of incorporated stem cells. The mesocrystals provide appropriate surfaces not only for binding of proteins but also for adhesion of cells, emphasizing the significance of mesoscience covering 100 nm–10 μm in the interactions between materials and cells.