Superficially porous poly(lactic-co-glycolic acid)/calcium carbonate microsphere developed by spontaneous pore-forming method for bone repair

Biodegradable polymer microspheres have been increasingly attracting attention in bone repair. In this work, superficially porous poly(lactic-co-glycolic acid)/calcium carbonate (PLGA/CC) composite microsphere is prepared by spontaneous pore-forming emulsion method. In addition to being the component that neutralizes the acidic products from PLGA degradation, calcium carbonate (CC) also constructs macropores on the surface of microsphere and thus exempts the use of extraneous porogens, which simplifies the preparation process and avoids problems related to extraneous porogen. It is found that the size of CC plays the most essential role in forming the superficial macropores because it determines the water absorption capacity of CC. Release of dexamethasone from the superficially porous composite microspheres shows a mild burst and the subsequent tri-phase profile. Meanwhile, the cell culture test demonstrates that MG-63 cells grow well on the superficially porous composite microsphere and proliferate better than those on pure PLGA microsphere. Therefore, this versatile composite microsphere has a promising application for bone repair.