Functionalizing titanium surface with PAMAM dendrimer and human BMP2 gene via layer-by-layer assembly for enhanced osteogenesis.

The study reports on the gene functionalization of titanium substrates with multilayered functional human BMP2 (hBMP2) gene plasmid and its effects on osteogenesis in vitro and in vivo. The multilayers comprising cationic poly(amidoamine) (PAMAM) dendrimer/EGFP-hBMP2 plasmid DNA complex (d-DNA) and anionic naked plasmid were deposited on titanium substrates via layer-by-layer (LbL) assembly technique, which was revealed by atomic force microscopy (AFM), water contact angle measurement, and release profiles. The expression of marker gene EGFP and functional gene hBMP2 were observed in osteoblasts. The assays of alkaline phosphatase activity, collagen secretion, ECM mineralization, and osteogenesis-related genes expression indicated that the multilayered structure improved the osteogenic differentiation in vitro. Moreover, the femur and subcutaneous transplantation of multilayered titanium implants were also investigated to reveal osteogenesis peri-implant by using histological examination and X-ray imaging. The in vivo histologic results showed that the BMP2 group (containing functional gene hBMP2) resulted in improved osteogenic proteins expression in subcutaneous and femur tissue, as well as high level of bone formation and % bone-implant contact (%BIC) peri-implant. The study offers an effective dendrimer and hBMP2 based strategy for surface functionalization of titanium implants in potential orthopedic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 706-717, 2018.