Cation regulated antibacterial activity of CuS/SnS2/ZnS/NiS nanomaterials via DHE mediated ROS generation and membrane lysis studies: An experimental and computational investigation.

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.