Bacteria- and Fungicidal Action of Ag, Au, ZnO, SiO₂ Nanoparticles in Presence of Carboxylic Acid in Polymer Matrix

Polymer nanocomposites based on different nanoparticles are intensively investigated for biomedical application due to the plenty of unique antimicrobial properties to gram-positive, gram-negative pathogens and fungi. Antibacterial and antifungal activity against wide range of microorganisms as well as the long-term activity (for a few months) is the main advantage of nanocomposites. The paper describes results of antifungal and antibacterial effects exhibited by acrylic nanocomposites contained Ag, Au, SiO₂, ZnO nanoparticles. Agar diffusion test was carried out for the nanomaterial bioactivity study. Candida albicans (C. albicans) and Aspergillus fumigatus (A. fumigatus) strain of fungi and staphylococci were used as a test objects. We found the strong antifungal and antibacterial activity of ZnO nanoparticles at presence of polymerized carboxylic acid in polymer matrix and the absence of such effects for pH neutral matrix. Possible explanations of semiconductor oxide nanoparticles antifungal and antibacterial activity were discussed in detail and related to the result of consequent chemical mechanism of water photolysis on semiconductor oxide nanoparticle surface, hydrogen peroxide production, its chemical reaction with polymer matrix, depolymerization, production of monomeric carboxylic acid and its reaction with Zn on nanoparticles surface and, finally, production of Zn organic salt, acting as biocidal agent. Nanocomposite weight loss measurements and pH changes processing by water confirm proposed explanation.