Response of MG63 osteoblast-like cells to titanium and titanium alloy is dependent on surface roughness and composition

The success of an implant is determined by its integration into the tissue surrounding the biomaterial. Surface roughness and composition are consider ed to influence the properties of adherent cells. The aim of this study was to determine the effect of chemical composition and surface roughness of c ommercially pure titanium (Ti) and Ti-6Al-4V alloy (Ti-A) on MG63 osteoblas t-like cells. Unalloyed and alloyed Ti disks were machined and either fine- polished or wet-ground, resulting in smooth (S) and rough (R) finishes, res pectively. Standard tissue culture plastic was used as a control. Surface t opography and profile were evaluated by cold field emission scanning electr on microscopy and profilometry, while chemical composition was determined u sing Auger electron spectroscopy and Fourier transform infrared spectroscop y. The effect on the cells was evaluated 24 h postconfluence by measuring c ell number, [H-3]-thymidine incorporation into DNA, cell and cell layer alk aline phosphatase specific activity (ALPase), osteocalcin and collagen prod uction, [S-35]-sulfate incorporation into proteoglycan, and prostaglandin E -2 (PGE(2)) and transforming growth factor-beta (TGF-beta) production. When compared to plastic, the number of cells was reduced on the pure Ti surfac es, while it was equivalent on the Ti-A surfaces; [H-3]-thymidine incorpora tion was reduced on all surfaces. The stimulatory effect of surface roughne ss on ALPase in isolated cells and the cell layer was more pronounced on th e rougher surfaces, with enzyme activity on TI-R being greater than on TfA- R. Osteocalcin production was increased only on the TI-R surface. Collagen production was decreased on Ti surfaces except Ti-R; [S-35]-sulfate incorpo ration was reduced on all surfaces. Surface roughness affected local factor production (TGF-beta, PGE(2)). The stimulatory effect of the rougher surfa ces on PGE(2) and TGF-beta was greater on Ti than Ti-A. In summary, cell pr oliferation, differentiation, protein synthesis and local factor production were affected by surface roughness and composition. Enhanced differentiati on of cells grown on rough vs. smooth surfaces for both Ti and Ti-A surface s was indicated by decreased proliferation and increased ALPase and osteoca lcin production. Local factor production was also enhanced on rough surface s, supporting the contention that these cells are more differentiated. Surf ace composition also played a role in cell differentiation, since cells cul tured on Ti-R surfaces produced more ALPase than those cultured on Ti-A-R. While it is still unknown which material properties induce which cellular r esponses, this study suggests that surface roughness and composition may pl ay a major role and that the best design for an orthopaedic implant is a pu re titanium surface with a rough microtopography. (C) 1998 Published by Els evier Science Ltd. All rights reserved.