Cytotoxicity of pristine and functionalized tungsten disulfide particles in the urinary system

Tungsten disulfide (WS2) particles have excellent lubrication properties and low surface energy. These features are exploited for numerous applications in the biomedical field, from the development of low-friction orthodontic wires to urinary encrustation-resisting coatings. Nevertheless, the cytotoxicity of spherical WS2 particles still remains unclear. We report the biocompatibility of pristine WS2 particles in human urinary bladder cells after the exposure to a wide range of concentrations (from 0 to 100 μg/mL). Based on the cell viability assessments using trypan blue exclusion assay and the PrestoBlue Cell viability reagent after 24, 48, and 72 h exposure, it can be concluded that these particle aggregates, with a diameter of ~ 500 nm, do not show any evidence of alterations or toxicity in the cells, even with high concentrations there exist a 87% of cell viability. Furthermore, due to the predisposition to agglomerate of this material and the possible use as a coating in urinary devices, we functionalized these particles with carboxylic groups. Aggregates with a diameter of ~ 370 nm were obtained. Zeta potential measurements highlighted that carboxylation correctly occurred, showing a switch from ~ + 4 for pristine particles to ~ − 35 for COOH-functionalized ones. Cytotoxic studies with these functionalized WS2 particles also showed good biocompatibility on human urinary bladder cells, with an 86% of viability after incubation with 100 μg/mL of particles over 72 h. These results highlight a good potential of WS2 particles for a future safe application as components of implantable medical devices.