Effects of surface micro-deformation on the cellular response to metallic implant materials

In the current study, it is aimed to get a comprehensive understanding of how cellular response to metallic biomaterial surfaces can be controlled via surface parameter specifics, as well as microstructural modifications. For this purpose, a surface micro-deformation procedure was designed where patterns with different parameters, specifically different indent size and repeating frequencies, were created on 316 L stainless steel sample surfaces by using a Vicker's microhardness testing device. The effects of the changes in surface properties following the formation of the different patterns were characterized via scanning electron microscopy (SEM), optical microscopy and profilometer. It was observed that surface roughness significantly increased as a result of the surface micro-deformation process and additionally, dislocation activities of different levels were triggered depending on the specifics of the formed micro-deformation pattern. The effects of the surface micro-deformation process on cellular response were investigated through in vitro experiments where Saos-2 cell line was used. Significant improvements were obtained in terms of cellular viability, proliferation, attachment and cell differentiation behaviors on the samples with surface micro-deformation. Correlating the effects surface parameters such as surface roughness, dislocation density close to the surface and topographical feature specifics on cellular response, it has been observed that by manipulating the metal microstructure and optimizing the surface microdeformation patterning parameters, cellular response can be significantly enhanced. It was shown that specific surface patterns with smaller indent depth and narrower spacings, as well as optimum dislocation density levels and surface roughness yields superior cellular response. Overall, the obtained information about the specifics of surface features of metallic biomaterials on cellular response can be used for the design of novel implant surface modification methods to improve osseointegration.