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

Abstract

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.