Development of a bioactive glass-based coating for implant application

Objectives: Although bioactive glass-based coating has attracted attention in the biomedical implant field, the adhesion of bioglass particles to titanium is weak and its effect under oral conditions remains unknown. To overcome such problem, this study used the plasma electrolytic oxidation (PEO) as a new route to develop an adherent mimetic bioactive glass coating. The morphology, chemical, mechanical and biological properties of the coating were investigated.

Methods: Commercially pure titanium (cpTi; Φ=10mm) discs were polished and PEO-treated to produce a bioactive glass-based coating (PEO-BG). Machined (cpTi) and sandblasted and acid-etched (SLA) discs were used as controls. Surfaces were characterized by scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), profilometry and wettability. Mechanical properties were assessed using Vickers microhardness, elastic modulus, coating thickness and coefficient of friction. For the biological properties, protein adsorption, hydroxyapatite formation, microbiological adhesion (2 h) and biofilm growth (24 h) were evaluated. Data were analyzed by ANOVA/Tukey HSD test (α=0.05).

Results: PEO-BG coating showed similar chemical composition to bioglass-45S5 (Si=45.2, Ca= 25.1, Na=20.0 and P=9.0 %w) and all bioactive elements were progressively released. PEO-BG surface morphology also presented high roughness, titanium crystalline phases (anatase and rutile) and superhydrophilic characteristic (Θw=0°). Compared with controls, PEO-BG enhanced microhardness, elastic modulus and coefficient of friction favoring higher wear resistance (P<.05). PEO-BG was not detrimental to blood plasma proteins adsorption, presented bioactive behavior and reduced initial adherence and oral biofilm growth compared to SLA surface (P<.05).
Conclusions: Bioglass-based coating was successfully synthesized via PEO on titanium. This new surface treatment was able to enhance the mechanical properties and biological responses compared to that of SLA and machined surfaces, being an alternative for biomedical implants application.