Substrate topography in the micrometer range is reviewed as a modifier of the response of cultured cells and of biocompatibility when implanted into tissues. Characterization methods for substrate topography are discussed, including scanning electron microscopy, profilometry, laser scanning, and confocal microscopy. Because of the current technical limitations in reproducing micron-level topographic details, only one method, ion-beam etching, has been found suitable for texturing substrates on nonplanar surfaces.

Collagen plays an important role in wound healing and as such is present in connective tissue capsules around implanted materials. The proportion of type I collagen to type III collagen is lower during wound healing than that found in normal dermis, but the amount of type I collagen gradually increases and type III decreases as healing continues. The intent of this research was to investigate a possible correlation between implant metals and type I and type III collagen formation in the ensuing soft-tissue capsules. Smooth implants of grade 4 commercially pure titanium and 316L stainless steel were placed via injection needle into the subcutaneous tissue of 12 rats for 6 weeks. The soft-tissue capsule that formed around each implant was evaluated histologically and by immunofluorescence. Although the two metal implant types differ in many respects, they were chosen for their differences in surface conductivity. Titanium oxide is semiconducting, whereas the oxide of stainless steel is conducting. Impedance spectroscopy was used for conductivity analysis of the surface. No qualitative differences were found in amount of type I or type III collagen in the capsules of the two metals. However, the capsules around titanium stained for type I collagen were thicker than capsules around stainless steel. In addition, type I collagen showed evidence of a greater association with densely packed, highly orientated collagen fibers.

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 142.157.212.158 On: Sun, 07 Dec 2014 16:05:49 42 KERNOHAN, BILLINGTON, AND LEWIS calculation would indicate that for each pair of defects created approximately 30 beryllium atoms in the form of the intermetallic compound Ni-Be precipitate from the solid solution.The mechanism whereby the precipitation is enhanced is not yet understood, but it might be assumed that the additional vacancies and/or interstitials made available by the neutron bombardment are responsible for an increased diffusion rate. It is not believed that "thermal spikes" playa role, because of the temperature depend-ence of the process. That is, a momentary high temperature "spike" should induce effects that are independent of temperature. ACKNOWLEDGMENTS