Photoluminescence in the characterization and early detection of biomimetic bone-like apatite formation on the surface of alkaline-treated titanium implant: State of the art

The possibility to use PL monitoring as an effective method and early detection tool of newly formed biomimetic apatite crystals were investigated through the intrinsic luminescence properties of apatite. The PL emission intensity increased as the exposure time in SBF increased. [Display omitted] ► A detectable biomimetic apatite layer was formed on the surface of alkaline-treated titanium implants early after immersion in SBF solution. ► The XRD patterns of the alkaline-treated titanium samples after immersion in SBF solution showed that before 3 days of immersion there is no detectable apatite peak clearly, however, the SEM observations showed that after the first day of immersion biomimetic apatite nanocrystals were formed. ► Early after immersion of titanium samples in the SBF solution, a broad emission peak centered at 592.5 nm was observed for biomimetic apatites as a function of exposure time, and the normalized PL intensity increased as the exposure time increased. Photoluminescence (PL) property is particularly important in the characterization of materials that contain significant proportions of noncrystalline components, multiple phases, or low concentrations of mineral phases. In this research, the ability of biomimetic bone-like apatite deposition on the surface of titanium alloy (Ti6Al4V) substrates in simulated body fluid (SBF) right after alkaline-treatment and subsequent heat-treatment was studied by the inherent luminescence properties of apatite. For this purpose, the metallic substrates were treated in 5 M NaOH solution at 60 °C. Subsequently, the substrates were heat-treated at 600 °C for 1 h for consolidation of the sodium titanate hydrogel layer. Then, they were soaked in SBF for different periods of time. Finally, the possibility to use of PL monitoring as an effective method and early detection tool is discussed. According to the obtained results, it was concluded that the PL emission peak did not have any significant shift to the shorter or higher wavelengths, and the PL intensity increased as the exposure time increased. This research proved that the observed inherent PL of the newly formed apatite coatings might be of specific interest for histological probing and bone remodelling monitoring.