# Biogenic Gold Nanocrystals Knock Down Pseudomonas aeruginosa Virulence via Quorum-Sensing and Antibiofilm Potential

## TL;DR

This study shows that biogenic gold nanocrystals can reduce the virulence and biofilm formation of Pseudomonas aeruginosa by interfering with quorum-sensing mechanisms.

## Contribution

The novel contribution is the use of biogenic gold nanocrystals to inhibit quorum-sensing and biofilm formation in Pseudomonas aeruginosa.

## Key findings

- BGNCs inhibited quorum-sensing in Chromobacterium violaceum and Pseudomonas aeruginosa.
- BGNCs suppressed virulence-related gene expression in Pseudomonas aeruginosa.
- BGNCs show potential as nontoxic agents for surface sterilization in hospital infections.

## Abstract

Multidrug resistance has also been accompanied by the prolonged use of antibiotics that makes complications in treatment. Biofilm in pathogenic bacteria is the most serious challenge linked with chronic illnesses and also contributes to virulence and drug resistance. Several bacterial pathogens employ the Quorum-sensing (QS) mechanism to coordinate their collective behaviors like bioluminescence, virulence, and biofilm formation. Therefore, agents that inhibit or interfere with bacterial QS and biofilm formation are emerging as a new class of next-generation antibacterial. Recently, nanoparticles have been employed to improve the efficacy of existing antibacterial agents. In the present study, gold nanocrystals were synthesized by using Koelreuteria paniculata (KP) leaf extract. Synthesized nanocrystals were characterized by a face-centered cubic structure of ~20 nm by XRD, FTIR, Zeta sizer, and TEM. Biogenic Gold nanocrystals (BGNCs) exhibited extended QS inhibition in bio-indicator strains Chromobacterium violaceum and Pseudomonas aeruginosa biosensor strains. BGNCs strongly suppressed QS-controlled violacein production in C. violaceum CV026, and elastase, protease, pyocyanin, alginate, and biofilm formation in P. aeruginosa (PA01). In addition, BGNCs notably suppressed the relative expression of PA01 quorum sensing, biofilm-forming, and virulence-regulating genes, as quantified by qRT-PCR. As a result of the broad-spectrum suppression of QS and biofilm by BGNCs, it is anticipated that these nontoxic bioactive nanocrystals can be employed as surface sterilization agents in nosocomial infections.