Surface characterization of biomimetic hydroxyapatite-silver functionalized on polydopamine film

Abstract

Hydroxyapatite (HA) is a well known bioactive material in the application of coated orthopaedic and dental implants. Recently, biomimetic technique has been explored to deposit a stable carbonated HA on a metal surface, mimicking the properties of natural bone. The aim of this study is to surface characterize the biomimetic hydroxyapatite (HA) and metallized silver (Ag) functionalized on a polydopamine film grafted titanium alloy (Ti6Al4V). The Ti6Al4V disks were grafted with the polydopamine film to provide catechol/quinone groups for chemical binding process. The grafted surfaces were metallized with Ag in silver nitrate solution. The metallized surfaces were then grafted with the second layer of polydopamine film and further biomineralized with HA in 1.5 simulated body fluid (SBF) solution for 3 and 7 days. The chemical compositions and chemical functionalities of those functionalized surfaces were characterized by XPS, FTIR and EDS. The morphologies of the surfaces were viewed under SEM. Finally, the wettability properties of the surfaces were investigated by water contact angle analysis. The XPS results showed that the polydopamine films were grafted on the Ti6Al4V surfaces. The polydopamine films became the chemical binding medium for functionalization of Ag and HA as the existence of both elements were clarified in XPS and EDS data. The appearance of HA functional groups (phosphate groups) were only noticed on FTIR spectrum when the biomimetic process was performed at 7 days. The formation of biomimetic HA has produced a hydrophilic surface with an appearance of hemispherical lath-like HA structure which is crucial for osseointegration and bone growth stability.