Preliminary in vivo study of apatite and laminin-apatite composite layers on polymeric percutaneous implants

A polymeric material coated with a hydroxyapatite (HA) layer would be useful as a flexible percutaneous device with good biocompatibility and resistance to bacterial infection. We have recently developed a simple, safe, and mild coating process to form an HA layer on the surfaces of polymeric materials. In this study, our coating process was applied to an ethylene-vinyl alcohol copolymer film. The resulting HA-coated film was percutaneously implanted in the scalp of a rat to examine the stability and biocompatibility of the HA layer. From the results of histological analysis, the HA layer remained undissolved on the film surface under the skin tissue even 3 days after implantation. Owing to the good biocompatibility of HA, the HA-coated film suppressed a host's foreign-body response and integrated with the surrounding skin tissue for as long as 14 days, in a similar fashion to a conventional percutaneous device composed of ceramic HA. Immobilization of a cell adhesion protein, laminin, into the HA layer was found to improve the adhesion strength between the film and the surrounding skin tissue without compromising good biocompatibility of HA. Our coating process to form HA and laminin-HA composite layers would be useful in fabricating polymeric percutaneous devices with a reduced risk of bacterial infection, although further in vivo studies are required.