South Asian Journal of Research in Microbiology

Aims: This study aimed to synthesize silver nanoparticles (AgNPs) using Lactobacillus gasseri and to evaluate their antimicrobial, anti-biofilm, and cytotoxic properties after formulation into a Carbopol-based nanoemulsion.

Study Design: This was an experimental laboratory-based study involving synthesis, physicochemical characterization, and biological evaluation of silver nanoparticles.

Place and Duration of Study: Conducted at the Department of Biotechnology, Centre for Bioscience and Nanoscience Research from March to April 2025.

Methodology: Silver nanoparticles were synthesized using the probiotic strain Lactobacillus gasseri through a green synthesis approach and embedded into Carbopol 940 hydrogel. Characterization was performed using UV-Visible spectroscopy (200–600 nm), FTIR spectroscopy (4000–400 cm⁻¹), and FESEM, confirming the formation of spherical nanoparticles ranging from 60 to 140 nm. Anti-biofilm activity was assessed via crystal violet assay against bacterial biofilms at varying nanoparticle concentrations (10–50 µg/mL). Cytotoxicity was tested using the MTT assay on mammalian cells across concentrations ranging from 2 to 10 µg/mL.

Results: Biofilm inhibition increased in a dose-dependent manner, with maximum inhibition of 55.96% observed at 50 µg/mL (OD 0.181 vs. control OD 0.411). Cytotoxicity analysis revealed a mild reduction in cell viability, with values ranging from 11.26% to 19.56% as concentration increased from 2 µg/mL to 10 µg/mL. The results suggest that biosynthesized AgNPs are both biologically active and relatively safe at lower concentrations. Statistical analysis confirmed a significant inverse relationship between nanoparticle concentration and cell viability.

Conclusion: The study demonstrates that Lactobacillus gasseri-mediated green synthesis of AgNPs, followed by incorporation into a Carbopol-based Nano emulsion, yields a biocompatible formulation with promising antimicrobial and anti-biofilm efficacy. The moderate cytotoxicity observed at higher concentrations highlights the need for dose optimization to balance therapeutic benefits with safety. These findings indicate that the developed nanoemulsion holds strong potential for biomedical applications such as wound healing and prevention of biofilm-associated infections on medical devices.