Effect of Poly-L-Lysine coating on titanium osseointegration : from characterization to in vivo studies

Abstract Dental implant prostheses cannot preclude a correct and stable implant osseointegration, which is still a challenge and greatly depends on biomaterial-cell interface. Titanium (Ti) coating using polyelectrolyte poly-L-lysine (PLL) may represent an interesting and simple approach, to provide a charged surface net able to improve cell adherence. However, in vitro and in vivo effects of Ti coated with PLL have been poorly investigated. The aims of the present study are: a) to obtain and characterize, chemically and physically, Ti disks coated with PLL (TiPLL); b) to perform in vitro studies on osteoblast cell lines cytocompatibility and functionality (alkaline phosphatase (ALP) activity, calcium deposition, pro-inflammatory interleukin 6 production); c) to obtain in vivo evidence of osseointegration, using sheep animal model. XPS, AFM and contact angle analyses demonstrated that the Ti disk was successfully covered with PLL, providing higher hydrophilicity to Ti disk. No cellular toxicity, enhanced calcium deposition, and a decreased tendency towards interleuchin-6 production were observed in osteoblast seeded onto TiPLL. In vivo experiments showed cortical bone microhardeness at 3 months significantly improved in presence of PLL coating. PLL coating on Ti implants seemed to safely enhance calcium deposition and implant early osseointegration in animals, suggesting promising evidence to optimize the surface properties of dental implants.