An in vitro evaluation of the variation in surface characteristics of bioactive glass coated SS316L for load bearing application

Abstract The present communication reports the variation in surface characteristics of bilayered coating of phosphate-free bioactive glass (PFBG) on SS316L substrate at simulated conditions, w.r.t both pH and temperature, to understand suitability of the same for load bearing application. The coated substrates were subjected to both physiological (7.4) and pathophysiological (4.5) pH conditions, considering two working temperatures of 37 °C and 45 °C, related to the real time scenario, in the post implantation period. Herewith, a faster dissolution of the PFBG network could be obtained at higher temperature (45 °C) and acidic pH (4.5) conditions, leading to a degraded surface texture, while the same at 37 °C and pH 7.4, exhibited an almost intact surface. The observation was corroborated using atomic force microscopy which exhibited an exponential increase in the nanoscale surface roughness of the coating at lower pH and at higher temperature condition. The ionic (Ca2+) dissolution kinetics of the PFBG coating followed by their cellular interaction was assessed using MC3T3 cell line, which showed a distinct difference compared to the as prepared PFBG coated substrate. Further, we made an attempt to assess the role of the calcium binding protein, calmodulin and its major target, calcium-calmodulin kinase II alpha (CAMKIIα) in osteoblast (MC3T3) differentiation, cultured on the PFBG coated SS316L substrates, subject to the experimental parameters as abovementioned. The results indicate significance of the real time conditions at the site of application of a bioactive glass coating on load bearing SS316L based implant material.