Controlled release of BMP-2 from titanium with electrodeposition modification enhancing critical size bone formation

In this study, a porous Ti-alloy based implant with an interconnected channel structure (MAO-CaP-BMP2) is fabricated using a method combining 3D printing, microarc oxidation (MAO) treatment, and co-precipitation of Ca,P layer with BMP-2 technique. The macroporous structure with pore size of 600 μm made by 3D printing not only enhances the ingrowth of cells but also allows the formation of blood vessels inside the implant. As a result, the new bond formation is promoted. In addition, the microporous dioxide layer formed on the implant surface by MAO provides the sites for co-precipitation of Ca,P layer with BMP-2. The microstructure allows the prolonged release of BMP-2. Our results show that a sustained release of BMP-2 over 35 days is achieved for MAO-CaP-BMP2 group longer than Ti without MAO modification group and without Ca,P electrochemical deposition group. The slow release of BMP-2 at the bone/implant interface for a long period of time leads to enhancement of the osseointegration between the implant and surrounding bones. This result indicates that MAO-CaP-BMP2 is a good candidate of growth factor carrier. Successful regeneration of bone requires the concomitant processes of osteogenesis and neovascularization. MAO-CaP-BMP2 modified Ti-alloy implant is both osteoinductive and osteoconductive which can create better osteogenesis and angiogenesis. As a result, it can enhance bone formation.