Novel Lignin-Capped Silver Nanoparticles against Multidrug-Resistant Bacteria

Area of Science:

• Nanotechnology
• Materials Science
• Microbiology

Background:

• Antibiotic resistance is a growing global health crisis, necessitating new antimicrobial strategies.
• Multidrug-resistant (MDR) bacteria cause severe infections, increasing hospital stays and healthcare costs.
• Developing agents that overcome bacterial resistance and prevent further evolution is crucial.

Purpose of the Study:

• To synthesize and characterize stable, biocompatible silver-lignin nanoparticles (NPs) using a green synthesis method.
• To evaluate the antibacterial efficacy of silver-lignin NPs against a range of MDR clinical isolates.
• To assess the biocompatibility and anti-inflammatory potential of silver-lignin NPs.

Main Methods:

• Green synthesis of silver nanoparticles using lignin as reducing and capping agents.
• Characterization of silver-lignin NPs for size, stability, and biocompatibility.
• Testing antibacterial activity against MDR clinical isolates (e.g., *Staphylococcus aureus*, *Pseudomonas aeruginosa*) and assessing THP-1 cell viability.
• Measuring IL-10 cytokine secretion from THP-1 cells.
• Analyzing gene expression changes in *P. aeruginosa* upon exposure to silver-lignin NPs.

Main Results:

• Stable, biocompatible silver-lignin NPs (approx. 20 nm) were synthesized, showing no agglomeration after one year.
• Effective inhibition of MDR bacterial growth was observed at non-cytotoxic concentrations for human cells.
• Silver-lignin NPs significantly increased IL-10 secretion, indicating anti-inflammatory properties.
• Sublethal exposure to silver-lignin NPs upregulated efflux pump genes but downregulated other membrane protein genes in *P. aeruginosa*.

Conclusions:

• Silver-lignin NPs present a promising dual-action agent for combating MDR bacterial infections.
• The green synthesis approach offers a sustainable method for producing effective antimicrobial nanomaterials.
• Further research into the mechanisms of action and therapeutic applications is warranted.