Surface characteristics, corrosion resistance and MG63 osteoblast-like cells attachment behaviour of nano SiO2–ZrO2 coated 316L stainless steel

Abstract

Nano SiO₂ (NS), ZrO₂ (NZ) and SiO₂–ZrO₂ (NSZ) mixed oxide coatings on to 316L stainless steel (SS) were developed by a simple sol–gel technique with varying Si : Zr ratios (100 : 0, 70 : 30, 50 : 50 and 0 : 100). Surface characteristics, corrosion resistance and the initial cell attachment behaviour of MG63 osteoblasts are studied. The formation of the NSZ mixed oxide was ensured from the shift in the Si–O–Si_asym band to a lower wave number with increasing Zr content in attenuated total reflectance infra-red (ATR-IR) spectra. X-ray diffraction studies also further confirmed the formation of mixed oxides. The formation of a spherical particle with a nanometre scale was confirmed from scanning electron microscopy (SEM) images and the particle size reduced as the Zr content increased. The simulated body fluid (SBF) contact angle values of NS, NSZ-73 and NSZ-55 were reduced to about three and two times compared to NZ and uncoated 316L SS respectively. Potentiodynamic polarization studies revealed the lower corrosion current density (i_corr) values for all the coated 316L SS. In particular, NSZ coatings exhibited significant reduction in i_corr values, further confirming that the addition of Zr to NS improved their corrosion resistance in a SBF solution. The initial attachment of MG 63 osteoblast-like cells on uncoated and coated 316L SS was studied using fluorescent microscopy by nuclei and actin protein staining. The results showed that the cell attachments were good for NS, NSZ-73 and NSZ-55 with the development of actin stress fibres with flattened cell morphology. However, the cell attachment was not significant for NZ. The variation in cell attachment behaviour is attributed to the surface characteristics and hydrophilic/hydrophobic nature of the coatings.