Enzyme-Activated Biomimetic Vesicles Confining Mineralization for Bone Maturation

Inspired by the crucial role of matrix vesicles (MVs), a series of biomimetic vesicles (BVs) fabricated by calcium glycerophosphate (CaGP) modified polyurethane were designed to mediate the mineralization through in situ enzyme activation for bone therapy. In this study, alkaline phosphatase (ALP) was harbored in the porous BVs by adsorption (Ad-BVs) or entrapment (En-BVs). High encapsulation of ALP on En-BVs was effectively self-activating by calcium ions of CaGP-modified PU that specifically hydrolyzed the organophosphorus (CaGP) to inorganic phosphate, thus promoting the formation of the highly oriented bone-like apatite in vitro. Enzyme-catalyzed kinetics confirms the regulation of apatite crystallization by the synergistic action of self-activated ALP and the confined microcompartments of BVs. This leads to a supersaturated microenvironment, with the En-BVs group exhibiting inorganic phosphate (Pi) levels 4.19 times higher and Ca2+ levels 3.67 times higher than those of simulated body fluid (SBF). Of note, the En-BVs group exhibited excellent osteo-inducing differentiation of BMSCs in vitro and the highest maturity with reduced bone loss in rat femoral defect in vivo. This innovative strategy of biomimetic vesicles is expected to provide valuable insights into the enzyme-activated field of bone therapy.