Biocompatible NiTiO3–Dopamine nanocomposites for combating drug-resistant pathogens through membrane disruption and oxidative stress

The rising threat of multidrug-resistant pathogens poses a challenge to public health. Highlighting the urgent need for novel antimicrobial agents, this study reports the synthesis of NiTiO₃ nanoparticles and dopamine-functionalized NiTiO₃ nanocomposites. Structural and elemental confirmation was obtained through XPS studies, which confirmed the presence of Ni²⁺ and Ti⁴⁺ in the nanocomposite, along with C 1s and O 1s peaks corresponding to dopamine coating. Photoluminescence spectra revealed that the NiTiO₃–dopamine nanocomposite exhibits notable green emission bands at 510, 518, and 527 nm which arises from deep-level recombination associated with complex oxygen-related defects like oxygen vacancies. The NiTiO₃-dopamine exhibited enhanced antimicrobial activity against S. aureus, B. subtilis, K. pneumoniae, S. dysenteriae, and C. albicans, compared to NiTiO₃ alone. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays further revealed that NiTiO₃–dopamine achieved MIC at 600 μg/mL and MBC at 1000 μg/mL for K. pneumoniae, outperforming pure NiTiO₃. ROS assays confirmed oxidative stress-mediated antimicrobial action, with ROS levels significantly quenched in the presence of histidine. SEM images of bacterial morphology showed extensive membrane disruption in NiTiO₃–dopamine treated cells. Furthermore, zebrafish embryo assays confirmed excellent biocompatibility of the NiTiO₃–dopamine nanocomposite, with normal development observed up to 72 h post fertilization.