Evaluation of the Antimicrobial Activity of Bimetallic TiO2-ZnO Nanoparticles Phytosynthesized with Ruta graveolens Extract Supported on a Chitosan Film

In this work, bimetallic TiO₂-ZnO nanoparticles were phytosynthesized in molar ratios of 1Ti:1Zn, 2Ti:1Zn, and 1Ti:2Zn, using plant extract of <i>Ruta graveolens</i> leaves as reductant agent. The TiO₂-ZnO nanoparticles were supported on chitosan films at concentrations of 0.1 and 0.2% (<i>w</i>/<i>v</i>). The resulting films were characterized by FTIR, TGA-DT and DSC analysis, confirming an adequate impregnation of the nanoparticles in the polymeric matrix and stability against temperature variations, while swelling tests revealed good structural strength without appreciable deformation. The antimicrobial activity of the membranes was evaluated by the disk diffusion method (Kirby-Bauer) against <i>Escherichia coli</i>, <i>Staphylococcus aureus</i> and <i>Candida albicans</i>. It was observed that the membranes having nanoparticles of stoichiometric ratios 1Ti:1Zn and 2Ti:1Zn presented higher microbicidal activity, especially against Gram-positive bacteria and yeast. The microbicidal effect of TiO₂-ZnO nanoparticles varies with each strain. The inhibition halo of the 2Ti:1Zn sample grow up to 14% in most tests, while the 1Ti:2Zn sample produces the smallest halo for <i>E</i>. <i>coli</i> and <i>C</i>. <i>albicans</i>; however, for <i>S</i>. <i>aureus</i>, the halo improves by up to 33%. This phenomenon is attributed to the stoichiometric arrangement capable of inducing oxidative stress. The results show the potential of chitosan films impregnated with TiO₂-ZnO NPs as functional materials for biomedical applications, especially in the development of dressings with enhanced antimicrobial properties.