The Conditions Matter: The Toxicity of Titanium Trisulfide Nanoribbons to Bacteria E. coli Changes Dramatically Depending on the Chemical Environment and the Storage Time

In this work, we present an analysis of the antibacterial activity of TiS3 nanostructures in water and 0.9% NaCl solution suspensions. TiS3 nanoribbons 1-10 mu m long, 100-300 nm wide, and less than 100 nm thick were produced by the direct reaction of pure titanium powder with elemental sulphur in a quartz tube sealed under vacuum. For the toxicity test of a bioluminescent strain of E. coli we used concentrations from 1 to 0.0001 g L-1 and also studied fresh suspensions and suspensions left for 24 h. The strongest toxic effect was observed in freshly prepared water solutions where the luminescence of bacteria decreased by more than 75%. When saline solution was substituted for water or when the solutions were stored for 24 h it resulted in a considerable decrease in the TiS3 antibacterial effect. The toxicity of TiS3 in water exceeded the toxicity of the reference TiO2 nanoparticles, though when saline solution was used instead of water the opposite results were observed. In addition, we did not find a relationship between the antibacterial activity of water suspensions of nanoribbons and the stability of their colloidal systems, which indicates an insignificant contribution to the toxicity of aggregation processes. In 0.9% NaCl solution suspensions, toxicity increased in proportion to the increase in the zeta potential. We suppose that the noted specificity of toxicity is associated with the emission of hydrogen sulphide molecules from the surface of nanoribbons, which, depending on the concentration, can either decrease or increase oxidative stress, which is considered the key mechanism of nanomaterial cytotoxicity. However, the exact underlying mechanisms need further investigation. Thus, we have shown an important role of the dispersion medium and the period of storage in the antibacterial activity of TiS3 nanoribbons. Our results could be used in nanotoxicological studies of other two-dimensional nanomaterials, and for the development of novel antibacterial substances and other biomedical applications of this two-dimensional material.

Automated summary

In this study, the antibacterial activity of TiS3 nanostructures in water and 0.9% NaCl solution suspensions was analyzed. The results showed that freshly prepared water solutions of TiS3 had the strongest toxicity against E. coli, but the antibacterial effect decreased significantly when the solutions were stored for 24 h or when saline solution was used instead of water. The toxicity of TiS3 in water was higher than that of TiO2 nanoparticles, but the opposite results were observed when saline solution was used. Additionally, there was no correlation between the antibacterial activity of water suspensions of nanoribbons and the stability of their colloidal systems, indicating a negligible contribution of aggregation processes to toxicity. In 0.9% NaCl solution suspensions, toxicity increased proportionally with the increase in zeta potential. It was hypothesized that the specificity of toxicity might be associated with the emission of hydrogen sulphide molecules from the surface of nanoribbons, which could either decrease or increase oxidative stress depending on the concentration. However, further investigation is needed to understand the exact underlying mechanisms. These findings highlight the importance of dispersion medium and storage period in the antibacterial activity of TiS3 nanoribbons, and have implications for nanotoxicological studies and the development of antibacterial substances and biomedical applications.