UV-Induced Antibacterial Activity of Green-Synthesized TiO2 Nanoparticles for the Potential Reuse of Raw Surface and Underground Water

The pollution of raw surface and underground water with pharmaceutical compounds has an impact on increasing the resistance of pathogenic microorganisms. Environmental challenges include investigating a novel and cost-effective therapeutic approach for the bactericidal treatment of water supplies. Ethyl acetate extracts from three marine algae (Caulerpa racemosa, Codium fragile, and Cystoseira myrica) obtained from the Red Sea (Hurghada, Egypt) were used for the green synthesis of TiO₂ nanoparticles (TiO₂-NPs). A highly crystalline nanoparticle structure with a stable tetragonal anatase structure was obtained; the mean concentrations were 2.43 to 6.09?×?10⁸ NPs/mL and the average particle size was 125–131 nm. In ultrapure water, the TiO₂-NPs were confirmed to be a stable solution following zeta potential analysis. UV light (λ?=?350 nm) for 2 h was used to activate the TiO₂-NPs before the antibacterial activity tests. The application of UV-activated TiO₂-NPs for 4 h treatments demonstrated promising bactericidal activity, with a 73.08% reduction in Salmonella typhi and a 91.51% reduction in Enterobacter ludwigii. Antibiofilm activities against the reference strains Salmonella typhi NCTC 12023/ATTC and Morganella morganii ATCC25829 and the bacterial isolates Klebsiella pneumoniae, Enterobacter ludwigii, and Enterococcus faecium were tested. The TiO₂-NPs were nontoxic against the human normal cell line RPE1. Regarding the treatment of total and fecal coliform, in addition to fecal streptococci, in raw surface and underground water, the UV-activated TiO₂-NPs prepared from the ethyl acetate extracts of Caulerpa racemosa showed high applicability. The present study offered insights into the nature and development of nontoxic and green TiO₂-NP formulations for use as modern antibacterial alternatives against coliforms in aquatic systems.