Influence of surface modification on biomimetic apatite deposition on glassy carbon: an in vitro study

Abstract In this in vitro study, glassy carbon (GC) substrates measuring approximately 1 cm × 0.5 cm were immersed in 1.5 × simulated body fluid (SBF), a supersaturated solution, to enable the formation biomimetic apatite coatings. Prior to immersion, the GC substrates were subjected to surface pre-treatments, one set was mechanical polished and another set was plasma etched. The pre-treated samples were then immersed in the SBF for 56 days to allow apatite deposition under controlled conditions. Structural, chemical, and mechanical characteristics of the resulting coatings were systematically investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and microfocus X-ray computed tomography (micro-CT). The plasma-etched surface showed a more dense and uniform apatite layer formed. It also had a higher Ca and P wt % however a lower crystallinity index compared to the polished sample. Micro-CT revealed increased coating porosity on the plasma-etched substrate indicating differences in coating architecture and interfacial characteristics. AFM also revealed plasma etching to increase the surface roughness and adhesion of the surface, suggesting improved coating-substrate interfacial stability.