Engineering the surface of titanium to improve its bioactivity and antibacterial activity through a multi-functional coating approach

Abstract

The present study reports the development of multi-functional coatings on titanium for orthopaedic implant applications. The multi-functional coating approach involves the development of TiO2 nanotubes by anodization followed by dip coating of polycaprolactone (PCL) in which the polymer matrix is incorporated with bioglass (BG), Ag doped bioglass (AgBG), Ag doped bioglass-graphene oxide (AgBG-GO), Ag doped bioglass-reduced graphene oxide (AgBG-rGO) and bioglass-silver functionalized reduced graphene oxide (BG-AgrGO). The structural and morphological characteristics, bioactivity and antibacterial activity of the multi-functional coatings were evaluated. The AgBG-GO/PCL and BG-AgrGO/PCL composite coatings exhibit better antibacterial activity than the AgBG/PCL and AgBG-rGO/PCL composite coatings. Among them, the BG-AgrGO/PCL composite coating with higher loading and slow release of silver ions is suitable for long term antibiotic delivery. The BG-AgrGO/PCL composite coating shows a Ca/P ratio of 1.53. The formation of Ca-deficient apatite of this composite coating suggests that the AgrGO did not hinder the bioactivity. Further, rGO nanosheets enable a higher loading of Ag and the persistence of 0.98 at% of Ag even after 10 days of immersion reveals sustained release of antibiotics in the physiological medium. The retention of coarse BG particles and the lower number of oxygen functional groups of rGO and AgrGO could have limited the dissolution of BG particles in the AgBG-rGO/PCL and BG-AgrGO/PCL composite coatings even after 14 days of immersion in HBSS. With a higher loading, slow release of antibiotics and having adequate bioactivity, the BG-AgrGO/PCL composite coating can be considered as a potential candidate for biomedical implant materials.