Abstract
The present study evaluated the efficacy of Y2O3:Tb (core) and Y2O3:Tb@SiO2 nanospheres (core/shell NSs) against virulence functions regulated by quorum sensing (QS) and biofilm formation in pathogenic bacteria. Scanning electron microscope (SEM) images were used to study the size, shape, and morphology. The images clearly displayed spherical shaped, mono-dispersed particles with narrow size distribution and an average grain size of 110–130 nm. The chemical composition of the samples was determined by using energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). We determined the impact of core and core/shell NSs on QS using sensor strains of Chromobacterium violaceum CVO26 and Pseudomonas aeruginosa PAO1 in a comparative study. Sub-MICs of core and core/shell NSs substantially suppressed QS-controlled violacein production in C. violaceum. Similar concentration-dependent effect of sub-MICs of synthesized core and core/shell NSs was observed in the QS-regulated virulence functions (elastase, total protease, pyocyanin production, swarming motility, and exopolysaccharide production) in PAO1. A concentration-dependent decrease (14–60%) was recorded in the biofilm forming capability of PAO1, upon treatment with core and core/shell NSs. Moreover, core/shell NSs were more effective in inhibiting biofilm at higher tested concentrations as compared to core-NSs. The synthesized NSs demonstrated significantly impaired attachment of cells to the microtiter plate indicating that NSs target biofilm inhibition at the attachment stage. Based on these results, we predict that core and core/shell NSs may be an alternative to combat the threat of drug-resistant pathogenic bacteria.
Highlights
The present study evaluated the efficacy of Y2O3:Tb and Y2O3:Tb@SiO2 nanospheres against virulence functions regulated by quorum sensing (QS) and biofilm formation in pathogenic bacteria
The depletion of the antibiotic arsenal and the continuous rise in resistance has led to the exploration of novel antibacterial therapeutics that are refractory to the development of antibiotic resistance mechanisms[2,3,4]
Targeting QS is advantageous over conventional anti-bacterial strategies, as the former treatment does not involve the suppression of bacterial growth and does not exert a selective pressure, which may lead to the development of resistance[12,13]
Summary
The present study evaluated the efficacy of Y2O3:Tb (core) and Y2O3:Tb@SiO2 nanospheres (core/ shell NSs) against virulence functions regulated by quorum sensing (QS) and biofilm formation in pathogenic bacteria. Targeting QS is advantageous over conventional anti-bacterial strategies, as the former treatment does not involve the suppression of bacterial growth and does not exert a selective pressure, which may lead to the development of resistance[12,13] In this context, the use of nanomaterials as potential quorum sensing inhibitors (QSIs) against nosocomial pathogens including Pseudomonas aeruginosa, is being explored by researchers[14]. We chemically synthesized and characterized the core and core/shell NSs. Scanning electron microscopic images and X-ray photoelectron spectroscopy were used to determine the size, shape, surface morphology and chemical composition of the prepared NSs. In a comparative study, we evaluated the efficacy of core and core/shell NSs against QS mediated virulence factors and biofilm formation in gram-negative pathogens. These findings suggest that chemically synthesized metal oxide NSs could be exploited in medical settings as well in the food & beverage industries for removal of microorganisms
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