Tuning antibacterial efficacy against Pseudomonas aeruginosa by using green AgNPs in chitosan thin films as a plastic alternative

Abstract

Nanotechnology advancements have facilitated the development of eco-friendly strategies to combat bacterial infections caused by antibiotic-resistant pathogens. This study promotes a green method for the synthesis of silver nanoparticles (AgNPs) utilizing Eucalyptus globulus leaf extracts as an alternative to traditional colloidal AgNPs obtained through chemical synthesis, investigating their antibacterial efficacy against Pseudomonas aeruginosa and their impact on the expression of bacterial virulence factors (pyocyanin, pyoverdine, rhamnolipids). This work demonstrates that: i. while colloidal AgNPs showed ineffective up to 120 μM, green AgNPs had a bactericidal effect already at 20 μM, without impacting bacterial virulence factors at sub-inhibitory concentrations; ii. the polyphenolic shell surrounding green AgNPs could play a crucial role in the antibacterial mechanisms, with a pro-oxidant action confirmed by a greater sensitivity to hydrogen peroxide (H₂O₂); iii. AgNPs improved the antibacterial properties of chitosan when incorporated into thin films. Consequently, an environmentally friendly nanocomposite film with antibacterial and antibiofilm properties was produced, which holds promise for application in food packaging to mitigate the emergence of microbial contamination in food products.