A dual-delivery system of pH-responsive chitosan-functionalized mesoporous silica nanoparticles bearing BMP-2 and dexamethasone for enhanced bone regeneration.

Bone morphogenetic protein-2 (BMP-2) is considered one of the most effective and extensively used growth factors to induce osteoblast differentiation and accelerate bone regeneration. Dexamethasone (Dex) with suitable dosage can enhance BMP-2-induced osteoblast differentiation. To strengthen this synergistic osteoinductive effect, a pH-responsive chitosan-functionalized mesoporous silica nanoparticle (chi-MSN) ensemble was fabricated for dual-delivery of BMP-2 and Dex. The MSNs are prepared by a CTAB-templated sol-gel method, and further coated by chitosan via the crosslinking of glycidoxypropyltrimethoxysilane (GPTMS). The small Dex is encapsulated in the mesopores and the large BMP-2 is incorporated into the chitosan coating. These chi-MSNs can quickly release BMP-2 in a bioactive form and can then be efficiently endocytosed and further realize a controlled release of Dex with the decreased pH value into/in cells. With the synergistic action of BMP-2 and Dex outside and inside the cell, this dual hybrid delivery system can significantly stimulate osteoblast differentiation and bone regeneration in vitro and in vivo. Together, this dual-delivery strategy for osteogenic protein delivery may enhance clinical outcomes by retaining the bioactivity and optimizing the release mode of the drug/protein.