Green fabrication and antibacterial evaluation of lysozyme-immobilized cysteine-capped silver nanoparticles.

Abstract

Aim: The broad-spectrum antibacterial properties of silver nanoparticles (AgNPs) are attracting increasing attention as a means to combat drug-resistant infections. Herein, we describe the green production of AgNPs with minimal environmental impact by using plant components as reducing agents.

Methods and results: Hibiscus rosa sinensis flower extract was used to form AgNPs from a 1 mM solution of silver nitrate. The NPs were cysteine-stabilized, on which hen egg white lysozyme was immobilized. The NPs, as analyzed by SEM, were nearly spherical. The size of the Cys-NPs, as measured by TEM, ranged from 12.52 nm to 27.20 nm, with an average size of 22.83, and the size of Lys-Cys-AgNPs ranged from 16.32 nm to 44.60 nm, with an average size of 30.30 nm. The enzyme assay for Lys-Cys-AgNPs demonstrated an effective activity of approximately 80.8 ± 3.6% compared to free lysozyme, and the immobilization efficiency was calculated to be 66.8%. MIC of Lys-Cys-AgNPs against E. coli (8.5 μg/mL), P. aeruginosa (12 μg/mL), S.aureus (6 μg/mL) and S. mutans (5.5 μg/mL). The antibacterial activity of Lys-Cys-AgNPs combined with streptomycin was evaluated against E. coli, P. aeruginosa, S. aureus, and S. mutans using the agar well diffusion method. The zones of inhibition observed were 11.00 ± 0.31 mm, 8.00 ± 0.11 mm, 8.00 ± 0.14 mm and 18.00 ± 0.65 mm, respectively.

Conclusion: Green-synthesized, cysteine-stabilized silver nanoparticles functionalized with lysozyme demonstrated enhanced antibacterial efficacy against both Gram-positive and Gram-negative pathogens. These findings highlight their potential as an eco-friendly and effective nanobiotherapeutic strategy to combat drug-resistant infections.