Enhanced antibacterial efficacy of selective laser melting titanium surface with nanophase calcium phosphate embedded to TiO2 nanotubes

Selective laser melting (SLM) has promising prospects in manufacturing customized implants, however the rough surface of SLM titanium specimen can facilitate bacterial adherence and biofilm formation, which is a risk to implant success. Therefore, surface modification is required to enhance its antibacterial efficacy. Sandblasting, anodization and electrochemical deposition were applied to construct a novel composite nanostructure of nanophase calcium phosphate embedded to TiO2 nanotubes on microrough SLM titanium substrates (NTN). NTN samples were compared with TiO2 nanotubes (NT) samples, mechanical polished (MP) samples and untreated SLM titanium samples. Surface characterization were analyzed using scanning electron microscope, energy dispersive spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, a three dimensional profilometer and a contact angle measuring device. Bacteria adhesion assay for bacteria colony counting and bacteria LIVE/DEAD staining was conducted using Streptococcus mutans and Streptococcus sanguinis. Both S. mutans and S. sanguinis adherence on SLM samples were significantly higher than on NTN, NT and MP samples. The antibacterial efficacy of NTN samples was superior compared to NT and had no significant difference with MP samples, despite the fact that NTN samples had much rougher surface than MP samples. This study elucidates an efficient method to enhance antibacterial efficacy on rough SLM surfaces, which contributes to its application in dental and other biomedical implants.