Pro-inflammatory effects of TiO₂ nanoparticles observed in human periodontitis model

Objectives: To clarify the mechanism of titanium dioxide nanoparticles (TiO₂ NPs)-enhanced periodontal ligament inflammation, we investigated whether TiO₂ NPs stimulates the production of pro-inflammatory substances in a periodontitis model, i.e., interleukin 1β (IL-1β)-treated human periodontal ligament fibroblast (HPLF).
Methods: The relative viable cell number was determined by MTT method. Extracellular concentration of prostaglandin E₂ (PGE₂) was determined by ELISA. Expression of cyclooxygenase-1 (COX-1) and COX-2 proteins was assessed by Western blot analysis. Fine cellular structure and intracellular incorporation of TiO₂ NPs were observed under transmission electron microscope (TEM).
Results: TiO₂ NPs were incorporated into the vacuoles of HPLF cells. TiO₂ NPs, at non-cytotoxic concentration, significantly enhanced both IL-1β-induced PGE₂ production and COX-1/COX-2 protein expression.
Conclusions: The present study suggests the possible aggravation of periodontitis by TiO₂ NPs, similar to our recent finding in gingivitis model (García-Contreras et al., Biomaterials 57, 33-40, 2015). We recommend careful use of dental materials containing TiO₂ NPs towards patients with periodontitis as well as gingivitis.