Multifunctional gradient coatings of phosphate-free bioactive glass on SS316L biomedical implant materials for improved fixation

A simple technique of applying porous (2-15 μm pore diameter) bi-layered vitreous coatings with phosphate free bioactive glass (PFBG) on surgical grade SS316L substrates by conventional spray coating method is demonstrated. The adhesion strength of the topmost porous layer (55 μm thick) of PFBG to the underlying SS316L substrate was improved by providing an impervious 10-15 μm thick PFBG glass interface on the clean, sand blasted substrate surface. The thermal expansion coefficient of the PFBG glass composition was tailored to match the thermal properties of the metallic substrate. The adhesion strength was 160 N for the impervious layer (layer 1) and 128 N for the porous coating (layer 2). The tensile strength for the top layer (layer 1) against the bottom layers was ~ 31.2 N mm− 2. The melting temperature of the glass (PFBG) was found to be ~ 800 °C from the differential thermal analysis study. The thermal expansion coefficient of the glass was matching to that of the metallic substrate (SS 316 L). In vitro cytotoxicity (ISO-10993-5, 1999) using the MC3T3 cell line exhibited excellent cellular response and cell viability. Cell adhesion tests indicated acceptable adhesion properties.