Cation regulated antibacterial activity of CuS/SnS₂/ZnS/NiS nanomaterials via DHE mediated ROS generation and...

CuS, SnS₂, ZnS and NiS nanoparticles were hydrothermally synthesised and characterised by UV-Visible, FTIR, XRD, HRSEM-EDS, ZETA Potential, BET and AAS-Solubility analytical techniques. SnS₂ showed larger specific surface area of 43.91 m²/g with crystallite size of 5.72 nm and exhibited relatively lower positive zeta potential of 23.63 mV. The ZnS showed lower specific area of 12.86 m²/g with a crystallite size of 15.31 nm and positive zeta potential of 25.34 mV. The AAS solubility test confirmed higher solubility of ZnS, forming free Zn²⁺ ions. The metal sulfides were investigated for antibacterial activity against Salmonella typhi, Staphylococcus aureus, and Vibrio cholera bacteria. The ZnS showed higher antibacterial activity against all bacteria despite a smaller surface area compared to SnS₂. The ROS formation was examined by Dihydroethidium (DHE) method, and bacterial membrane lysis was confirmed by trypan blue staining. The antibacterial efficacy of the investigated metal sulfides followed the order: ZnS > SnS₂>CuS > NiS. Molecular docking was performed to explore the binding ability of metal ions with the protein, compared with experimental results. For the docking studies, DNA gyrase subunit B protein was selected. The docking studies further revealed a higher binding affinity of ZnS compared to other metal sulfides. The binding affinities of ZnS, SnS₂, CuS and NiS were found to be -6.2 kcal/mol, -5.8 kcal/mol, -4.2 kcal/mol, and -5.2 kcal/mol, respectively. Therefore, the present work demonstrates and establishes a clear correlation between the nature of the cation in selected metal sulfides and the observed antibacterial activity through combined laboratory experiments and molecular docking studies.