Green synthesis of silver titanium dioxide nanocomposites functionalized with chitosan for enhanced antimicrobial and antioxidant activity.

This study reports the green synthesis of silver-titanium dioxide nanocomposites functionalized with chitosan (CS@Ag-TiO₂ NCs) using Moringa oleifera leaf extract (MOLE) as a natural reducing and stabilizing agent. The novelty of this work lies in integrating MOLE-mediated Ag-TiO₂ formation with chitosan surface functionalization to develop a bioactive nanocomposite with improved surface properties and biological performance compared with uncoated Ag-TiO₂ NCs. The synthesized nanocomposites were characterized using UV-Vis spectroscopy, FTIR, DLS, zeta potential, TEM, SEM, and EDX analyses. TEM and SEM showed irregular and predominantly spherical particles with sizes of 10-50 nm for Ag-TiO₂ NCs and 20-80 nm for CS@Ag-TiO₂ NCs. Zeta potential analysis confirmed surface charge reversal after chitosan coating, from -33.17 ± 1.46 mV for Ag-TiO₂ NCs to + 32.47 ± 3.21 mV for CS@Ag-TiO₂ NCs, supporting successful surface functionalization. CS@Ag-TiO₂ NCs showed stronger antioxidant activity than Ag-TiO₂ NCs, with IC₅₀ values of 4.27 and 6.14 µg/mL, respectively. The chitosan-functionalized nanocomposite also showed improved preliminary in vitro antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, with inhibition zones of 17 ± 1.0, 20 ± 1.5, and 16 ± 1.0 mm, respectively. These findings suggest that MOLE-assisted green synthesis combined with chitosan functionalization is a promising strategy for developing Ag-TiO₂-based nanocomposites with enhanced antioxidant and antimicrobial potential.