Synergistic Biocidal Effects of Curcumin, Chitosan, and Nickel Titanate-Based Nanohybrids for Enhanced Antibacterial and Anticancer Therapies

Microbial infections and colorectal cancer are significant contributors to mortality and morbidity, necessitating prompt action. In the present work, NiTiO₃ (NT), curcumin-loaded NiTiO₃ (CUNT), chitosan-loaded NiTiO₃ (CHNT), and both curcumin and chitosan-loaded NiTiO₃ (CUCHNT) hybrid nanomaterials (HNMs) were systematically prepared using <i>Psidium guajava</i> leaf extract. PXRD studies revealed that NT, CUNT, CHNT, and CUCHNT exhibited a rhombohedral structure with the <i>R</i>3̅ space group with mean crystallite sizes of ∼66.41, ∼61.94, ∼61.65, and ∼65.12 nm, respectively. Band gap energies were estimated as ∼3.10, ∼3.15, ∼3.14, and ∼3.15 eV for NT, CUNT, CHNT, and CUCHNT, respectively. Antibacterial efficacies of synthesized HNMs were analyzed against both Gram-positive (G+) and Gram-negative (G-) bacteria using the well diffusion method, and the zone of inhibition (ZOI) exhibited by NT, CUNT, CHNT, and CUCHNT against <i>Staphylococcus aureus</i> were 11.5, 13, 12, and 17.5 mm, respectively; those of <i>Staphylococcus pneumoniae</i> were 9, 13.5, 11, and 14 mm, respectively; those of <i>Klebsiella pneumoniae</i> were 10, 9.5, 10, and 17 mm, respectively; and those of <i>Escherichia coli</i> were 11, 11.5, 13, and 16.5 mm, respectively. ZOI results showed that CUCHNT HNMs have superior antibacterial efficacies for all tested bacterial strains compared to NT, CUNT, and CHNT. Cytotoxic capabilities of the synthesized HNMs were analyzed using the MTT assay against the HCT-116 colorectal carcinoma cell line. All HNMs showed significant anticancer activity, with CUCHNT exhibiting the most pronounced activity, having an IC₅₀ value of 87 μg/mL. Morphological changes and cell death mechanisms of synthesized HNMs were studied using dual AO/EtBr, H₂DCFDA, and JC-1 staining. These findings emphasize that biosynthesized CUCHNT HNMs using <i>P. guajava</i> leaf extract could be a potential therapeutic agent for antimicrobial and anticancer applications.