Stable Colloidal Copper Nanoparticles Functionalized with Siloxane Groups and Their Microbicidal Activity

Abstract

The emergence and spread of pathogenic microbes with resistance to multiple antibiotics necessitates the development of new broad-spectrum microbicides. Metal nanoparticles are one such microbicide and they have been recognized for their potential value in fighting harmful microbes. In this work, we show the preparation and antimicrobial characterization of copper nanoparticles, with a small percentage of copper (I) oxide, synthesized by a chemical method based on a bottom-up approach in a nonaqueous medium. In particular, we developed a new route to stabilize the copper nanoparticles, synthesized in ethanol, using an aminosilane as a capping agent. The particles were later centrifuged and suspended in ethylene glycol. The morphology, structure and stability of the Cu-APTMS NPs were characterized by UV?Vis and FTIR spectroscopy, TEM, AFM and GI-XRD techniques. The presence of colloidal nanoparticles was found 4 months after synthesization and a characteristic absorption LSPR band was registered in the UV?Vis spectrum. The Cu-APTMS NPs showed a significant in vitro degradation activity against bacterial DNA, which is important in vivo microbicidal activity. The Cu-APTMS NPs showed a strong bactericidal effect against planktonic forms of Gram-negative (Pseudomonas aeruginosa and enterohemorrhagic Escherichia coli) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. This bactericidal effect was also observed to severely limit the viability and germination proficiency of spores of the food-poisoning and gas-gangrene producer Clostridium perfringens. In addition, pathogenic fungi (Candida tropicalis and Fusarium verticillioides) were irreversibly deactivated by treatment with Cu-APTMS NPs.