Evaluation of nanodebris produced by in vitro degradation of titanium-based dental implants in the presence of bacteria using single particle and single cell inductively coupled plasma mass spectrometry

The bio-tribocorrosion of metallic materials used for dental implants (Ti and alloys) in the oral environment involves the production of metallic debris not only in the ionic, but also in the nanoparticulate form. The present work shows a systematic evaluation of the detection of Ti-containing nanoparticles in different biological media, including artificial saliva, in the presence of the mucosal bacterium Streptococcus mutans. The studies have been performed using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) complemented with transmission electron microscopy (TEM). The obtained results revealed lower aggregation when suspending standard TiO2 nanoparticles at neutral pH in artificial saliva and no additional effect on the agglomeration or particle size due to the presence of bacteria in the media. Then, different Ti-based dental implants made of an alloy of Ti, Al and V were incubated in the presence of artificial saliva for 48 hours to evaluate the in vitro release of metallic species. The presence of Ti-, Al- and V-containing nanoparticles was observed by SP-ICP-MS and the existence of such nanodebris was confirmed by TEM. The addition of mucosal bacteria to the media caused a significant decrease in the production of nanoparticles due to the formation of a biofilm on the surface of the incubated implants, which was further confirmed by confocal microscopy. The incubation of the implants released nanoparticles with osteoblast cells (Saos-2 cell culture) and further analysis by single-cell (SC)-ICP-MS revealed a significant uptake of the nanostructures by the bone cells with still unknown effects.