Synthesis and characterization of NiTiO₃-L-ornithine nanoparticles and their antibacterial, antifungal, antioxidant activities, and zebrafish biocompatibility.

The increasing prevalence of antimicrobial resistance and biofilm-associated infections demands multifunctional nanomaterials with improved efficacy and safety. In this study, defect-engineered nickel titanate (NiTiO₃) nanoparticles functionalized with L-Ornithine (NiTiO₃-LO) were synthesized via a co-precipitation approach to enhance antimicrobial performance while maintaining biocompatibility. XRD analysis confirmed phase-pure rhombohedral NiTiO₃ with reduced crystallite size upon functionalization (31.3 ± 2 nm to 26.2 ± 2 nm). XPS and FTIR analyses verified successful LO surface coordination and modulation of oxygen vacancy-related defect states. PL studies revealed defect-mediated green emissions (507-529 nm), indicating stabilized oxygen vacancies after functionalization. NiTiO₃-LO exhibited significantly enhanced antibacterial and antifungal activity, with inhibition zones of 17.9 ± 0.4 mm and 18.9 ± 0.4 mm, respectively. The nanoparticles also demonstrated concentration-dependent antioxidant activity, achieving ~ 63% DPPH scavenging at 100 µg/mL, comparable to Vitamin C (~ 65%). Importantly, zebrafish embryo assays showed no observable developmental toxicity, indicating favourable in vivo biocompatibility. These findings establish NiTiO₃-LO as a defect-modulated, multifunctional nanoplatform integrating antimicrobial, antioxidant, and biocompatible properties for potential biomedical applications.