Tolerability of N-chlorotaurine in comparison with routinely used antiseptics: an in vitro study on chondrocytes.

Background: Currently, povidone-iodine (PVP-I) and hydrogen peroxide (H₂O₂) are frequently used antiseptics in joint infections, but the cytotoxic effects of these solutions are already reported. N-chlorotaurine (NCT) shows a broad-spectrum bactericidal activity and is well tolerated in various tissues, but its effect on human chondrocytes is unknown. The purpose of this study was to assess the cytotoxic effect of NCT, PVP-I, and H₂O₂ on human chondrocytes compared to a control group in an in vitro setting to get first indications if NCT might be a promising antiseptic in the treatment of septic joint infections for the future.

Material and methods: Chondrocytes extracted from human cartilage were incubated with various concentrations of NCT, PVP-I, and H₂O₂ for 5 and 30 min respectively. EZ4U cell viability kit was used according to the manufacturer's recommendations determining cell viability. To assess cell viability based on their nuclear morphology, cells were stained with acridine-orange and identified under the fluorescence microscope.

Results: EZ4U kit showed after 5 and 30 min of incubation a significant decrease in cell viability at NCT 1%, NCT 0.1%, PVP-I, and H₂O₂, but not for NCT 0.001% and NCT 0.01%. Acridine-orange staining likewise presented a significant decrease in vital cells for all tested solutions except NCT 0.001% and NCT 0.01% after 5 and 30 min of incubation.

Conclusion: Our results demonstrate that NCT is well tolerated by chondrocytes in vitro at the tested lower NCT concentrations 0.01% and 0.001% in contrast to the higher NCT concentrations 1% and 0.1%, PVP-I (1.1%), and H₂O₂ (3%), for which a significant decrease in cell viability was detected. Considering that the in vivo tolerability is usually significantly higher, our findings could be an indication that cartilage tissue in vivo would tolerate the already clinically used 1% NCT solution. In combination with the broad-spectrum bactericidal activity, NCT may be a promising antiseptic for the treatment of septic joint infections.