Fig. 2.

Various aspects of dynamic microenvironment can influence the delivery of bone growth factor during bone healing. Osteoblasts and osteoclast directly participate in the catabolic and anabolic processes of bone formation. The carrier of the delivery system can directly control the release kinetics of the growth factors. pH at the bone defect sites can affect growth factor release by changing the degradation rate of the carrier. The presentation of growth factors to target cells is also modulated by ECM while ECM components is consistently remodeled by inflammatory and other types of cells via secretion of proteases such as MMPs. Besides, mechanical stimulus also play an importantly during the whole bone regeneration process.