Eliminating the negative effect of cold deformation on the corrosion resistance of austenitic stainless steel in the presence of a protein

In vitro contact guidance of glioblastoma cells on metallic biomaterials

Cancer cells' ability to sense their microenvironment and interpret these signals for the regulation of directional adhesion plays crucial role in cancer invasion. Furthermore, given the established influence of mechanical properties of the substrate on cell behavior, the present study aims to elucidate the relationship between the contact guidance of glioblastoma cell (GBM) and evolution of microstructural and mechanical properties of the implants. SEM analyses of the specimens subjected to 5 and 25% of plastic strains revealed directional groove-like structures in micro and submicro-sizes, respectively. Microscale cytoplasmic protrusions of GBMs showed elongation favored along the grooves created via deformation markings on 5% deformed sample. Whereas filopodia, submicro-sized protrusions facilitating cancer invasion, elongated in the direction perpendicular to the deformation markings on the 25% deformed sample, which might lead to easy and rapid retraction. Furthermore, number of cell attachment was 1.7-fold greater on 25% deformed sample, where these cells showed the greatest cellular aspect ratio. The directional attachment and contact guidance of GBMs was reported for the first time on metallic implants and these findings propose the idea that GBM response could be regulated by controlling the spacing of the deformation markings, namely the degree of plastic deformation. These findings can be applied in the design of cell-instructive implants for therapeutic purposes to suppress cancer dissemination.

Corrosion performance of various deformed surfaces of implant steel for coronary stent applications: Effect of protein concentration

This work was done to systematically elucidate the corrosion behavior of austenitic stainless steel subjected to various degree of cold deformation (10 %, 20 % & 30 %). The experiments were performed in phosphate buffer saline (PBS) solution having different concentrations of bovine serum albumin (0.2, 0.5, 1.0, 2.0, 4.0 g L^-1). Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) analysis were performed to obtain the corrosion parameters. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface morphologies and chemical compositions of the surface films. Contact angle analysis was also used to detect the hydrophilic character of sample surfaces. The BSA had a considerable effect of inhibition on the corrosion of SSs in annealed as well as in deformed state due to its adsorption on surface of steel. For annealed samples, at 4.0 g L^-1BSA concentration, the corrosion resistance was drastically decreased but interestingly not for sample with more than 10 % deformation and the concentration effect of BSA is also not very significant after 0.5 g L^-1 for deformed surfaces. The breakdown potential for 30 % deformed sample is quite higher in presence of BSA even at 4.0 g L^-1 while it is lowest for annealed samples in the same condition. The variation in contact angle with deformation is very less after adsorption of BSA. On the basis of the obtained results, mechanism aspect for corrosion of steel in presence of protein is also deliberated.