A light and electron microscopic study of the effects of surface topography on the behavior of cells attached to titanium‐coated percutaneous implants

Abstract

Previous studies using light microscopy have demonstrated that micromachined grooved surfaces inhibit epithelial (E) downgrowth and affect cell orientation at the tissue/implant interface. This study investigates the ultrastructure of the epithelial and connective-tissue attachment to titanium-coated micromachined grooved, as well as smooth control, implant surfaces. V-shaped grooves, 3, 10, or 22 microns deep, were produced in silicon wafers by micromachining, replicated in epoxy resin, and coated with 50-nm titanium. These grooved, as well as smooth, titanium-coated surfaces were implanted percutaneously in the parietal area of rats and after 7 days processed for electron microscopy. The tissue preparation technique used in this study enabled us to obtain ultrathin sections with few artifacts from the area of epithelial and connective-tissue attachment. The histological observations demonstrated that E cells closely attached to, and interdigitated with, the 3-microns and 10-microns grooves. In contrast, E cells were not found inside the 22-microns-deep grooves and made contact only with the flat ridges between the grooves. As a general rule, fibroblasts (F) were oriented parallel to the long axis of the implants and produced a connective tissue capsule with 3-microns and 10-microns-deep grooved surfaces as well as smooth surfaces. On the 22-microns-deep grooved surfaces, however, F inserted obliquely into the implant. The attachment of F to the titanium surface was mediated by two zones; a thin (approximately 20 nm), amorphous, electron dense zone immediately contacting the titanium surface, and a fine fibrillar zone extending from the amorphous zone to the cell membrane. As oblique orientation of F has been associated with the inhibition of epithelial downgrowth, micromachined grooved surfaces of appropriate dimensions have the potential to improve the performance of percutaneous devices.