Synthesis of Eco-friendly Silver Nanoparticles (AgNPs) by Lacticaseibacillus rhamnosus for Combating Antibiotic Resistance and Boosting Antioxidant Activity

Abstract

Antimicrobial resistance (AMR) is an imperative global health threat, prompting the need to design novel therapeutic options. In this work, silver nanoparticles (AgNPs) were biosynthesised from Lacticaseibacillus rhamnosus using a green synthesis method. Characterisation was ensured by a colour change visible to the naked eye and a UV–Visible absorption maximum at 429 nm. The antimicrobial activity of the biosynthesised AgNPs (AgNPs-LR) was tested against standard and multidrug-resistant (MDR) strains of bacteria through agar well diffusion and MIC assays. The findings showed potent, dose-dependent antibacterial potential, with clear zones of inhibition recorded in Escherichia coli (ESBL, 19 mm) and Klebsiella pneumoniae (MDR, 17 mm) at 150 µL. MIC analysis showed high sensitivity in E. coli and Pseudomonas aeruginosa ATCC strains (MIC <2 µg/mL), whereas Serratia marcescens and K. pneumoniae (MDR) were inhibited at ≤8 µg/mL, validating the broad-spectrum potential of AgNPs-LR, especially against Gram-negative and MDR pathogens. Gram-positive strains manifested variable resistance, suggesting the necessity for further optimisation of formulation. Moreover, AgNPs-LR manifested concentration-dependent antioxidant activity in the DPPH radical scavenging assay, exhibiting comparable performance to ascorbic acid at elevated concentrations. The above findings reinforce the dual functionality of AgNPs-LR as a potent antimicrobial and antioxidant compound, and thus underscore its potential as a viable candidate for the fight against AMR and oxidative stress management in biomedical applications.