Effects of pH on the silk fibroin coating of CoCrMo alloy

Bacteria related infections are still cited as a major problem for the implant materials resulting in failure of device especially knee and hip replacement. Two main approaches are focused for inhibiting the bacterial adhesion to the surface. These involve bactericidal substances and anti-adhesive coatings. Silk fibroin is one of the promising materials due to its good drug loading capacity and efficiency. In this study, the effects of pH on the silk fibroin coating of CoCrMo alloy, prepared by means of layer by layer, was investigated thoroughly using scanning electron microscope (SEM), Atomic Force Microscope (AFM) Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy. A medical grade CoCrMo was coated with variable number of silk fibroin up to 14 layers at pH 3.0, 3.5, and 5.5 at room temperature. As a result, only silk fibroin films prepared at pH 3.0 and 3.5 were found to convey the general characteristics of the mixture of silk I and II, while the samples prepared at pH 5.5 exhibited the lack of some specific amide structures which influence the general characteristics of silk I and II. Moreover, regardless of pH, the surface roughness was determined to increase with the increasing number of layers. However, as the pH increases the surface roughness decreases at 6, 10 and 14 layers.