Nano‐TiO₂ penetration of oral mucosa: in vitro analysis using 3D organotypic human buccal mucosa models

Abstract

BackgroundOral cavity is a doorway for a variety of products containing titanium dioxide (TiO2) nanoparticles (NPs) (nano‐TiO2) such as food additives, oral healthcare products and dental materials. Their potential to penetrate and affect normal human oral mucosa is not yet determined.ObjectivesTo evaluate the ability of nano‐TiO2 to penetrate the in vitro reconstructed normal human buccal mucosa (RNHBM).Methods RNHBM was generated from primary normal human oral keratinocytes and fibroblasts isolated from buccal oral mucosa of healthy patients (n = 6). The reconstructed tissues were exposed after 10 days to clinically relevant concentrations of spherical or spindle rutile nano‐TiO2 in suspension for short (20 min) and longer time (24 h). Ultrahigh‐resolution imaging (URI) microscopy (CytoViva™, Auburn, AL, USA) was used to assess the depth of penetration into reconstructed tissues.ResultsUltrahigh‐resolution imaging microscopy demonstrated the presence of nano‐TiO2 mostly in the epithelium of RNHBM at both 20 min and 24‐h exposure, and this was shape and doze dependent at 24 h of exposure. The depth of penetration diminished in time at higher concentrations. The exposed epithelium showed increased desquamation but preserved thickness.ConclusionNano‐TiO2 is able to penetrate RNHBM and to activate its barrier function in a doze‐ and time‐dependent manner.

Repeated exposure of Caco-2 versus Caco-2/HT29-MTX intestinal cell models to (nano)silver in vitro: Comparison of two commercially available colloidal silver products

“…CytoViva™ hyperspectral imaging was thus performed on Caco-2 and Caco-2/HT29-MTX cells repeatedly exposed to Mesosilver™ or AgC. CytoViva™ is a high contrast optical dark-field system , used in the nanotoxicology field for imaging TiO2 NPs (Konstantinova et al, 2017) and, more recently, AgNPs (Fizeşan et al, 2019;Mehennaoui et al, 2018). Nanoparticles and other light-scattering objects appear as bright features on a dark background; thus, fluorescent labelling of NPs, which could modify their physico-chemical properties, is not required.…”

Hepato(Geno)Toxicity Assessment of Nanoparticles in a HepG2 Liver Spheroid Model

“…However, when exposing the already formed spheroids for 24 h, NPs were seen only to a depth of 20 µm [26]. Cell types, cell densities, physicochemical characteristics of the NPs (including size distribution) and ion release may influence the penetration inside the spheroid [73][74][75][76][77].…”

Safety of titanium dioxide nanoparticles in cosmetics

“…In humans, a 3D organotypic human buccal mucosa model was used to access nano‐TiO 2 penetration in vitro . Nano‐TiO 2 penetrated the reconstituted human normal buccal epithelium, with most of the particles remaining in the upper third of the epithelial tissue . Another study assessed gastrointestinal absorption of nano‐TiO 2 in vivo : a single dose of nano‐TiO 2 (5 mg/kg bw), dispersed in water, was administered to nine subjects.…”

“…Nano-TiO 2 penetrated the reconstituted human normal buccal epithelium, with most of the particles remaining in the upper third of the epithelial tissue. 43 Another study assessed gastrointestinal absorption of nano-TiO 2 in vivo: a single dose of nano-TiO 2 (5 mg/kg bw), dispersed in water, was administered to nine subjects. Only negligible absorption of nano-TiO 2 via the gastrointestinal tract was observed after 2, 4, 24 and 48 h. 44 Currently available data thus showed nano-TiO 2 penetration through in vitro/ex vivo models of oral mucosa, but negligible nano-TiO 2 absorption, if any, via the gastrointestinal tract after oral exposure to nano-TiO 2 in vivo, either in rats or in humans.…”