Surface modifications of a silicalite film designed for coating orthopaedic implants

Abstract

The effect of various surface modifications of silicalite-1 film grown on a Ti6Al4V alloy on biocompatibility and cell differentiation has been addressed. The as-synthesized silicalite film was first modified by alkaline etching and by subsequent treatments in oxygen radiofrequency (O2 RF)plasma, by calcination at 500 °C, and by processing the calcinated samples in the O2 RFplasma. The chemical composition, crystallinity, topography and wettability of samples were characterized using angle-resolved X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and sessile water drop contact angle measurements. We have discovered the presence of a non-zeolitic defective SiOx phase (NZP) with coordinated hydrocarbon chains. The NZP can be removed by the exposition to the O2 RF plasma. The metabolic activity tests done on human osteoblast line Saos-2 revealed that the NZP can influence cell proliferation; however, all studied modifications of silicalite film can be considered biocompatible. The osteogenic differentiation was studied on human mesenchymal stem cells under static conditions and under dynamic (pulsatile and shear) stress. The results obtained by the real-time qPCR and immunofluorescence microscopy suggest that etched, plasma-treated and calcinated + plasma-treated samples are the most promising for osteogenic cell differentiation.