Abstract
Plant-based synthesis of eco-friendly nanoparticles has widespread applications in many fields, including medicine. Biofilm—a shield for pathogenic microorganisms—once formed, is difficult to destroy with antibiotics, making the pathogen resistant. Here, we synthesized gold nanoparticles (AuNPs) using the stem of an Ayurvedic medicinal plant, Tinospora cordifolia, and studied the action of AuNPs against Pseudomonas aeruginosa PAO1 biofilm. The synthesized AuNPs were characterized by techniques such as ultraviolet-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray diffraction, X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. The AuNPs were spherically shaped with an average size of 16.1 nm. Further, the subminimum inhibitory concentrations (MICs) of AuNPs (50, 100, and 150 µg/mL) greatly affected the biofilm-forming ability of P. aeruginosa, as observed by crystal violet assay and SEM, which showed a decrease in the number of biofilm-forming cells with increasing AuNP concentration. This was further justified by confocal laser scanning microscopy (CLSM), which showed irregularities in the structure of the biofilm at the sub-MIC of AuNPs. Further, the interaction of AuNPs with PAO1 at the highest sub-MIC (150 µg/mL) showed the internalization of the nanoparticles, probably affecting the tendency of PAO1 to colonize on the surface of the nanoparticles. This study suggests that green-synthesized AuNPs can be used as effective nano-antibiotics against biofilm-related infections caused by P. aeruginosa.
Highlights
Pseudomonas aeruginosa is an opportunistic pathogen and has become a model organism for biofilm research
Biofilms, formed by some microorganisms, are complex communities covered by self-made exopolysaccharide (EPS) layers, which are irreversibly attached to these surfaces [6]
The stem of T. cordifolia was collected from the nearby area of Aligarh, Uttar Pradesh, India
Summary
Pseudomonas aeruginosa is an opportunistic pathogen and has become a model organism for biofilm research. The ability of P. aeruginosa to form biofilms is a major virulence factor and is associated with nosocomial infections. Modification of enzymes, target-site mutation, and efflux pumps are important factors that contribute to the development of antibiotic resistance [4]. This bacterium can form biofilms on different surfaces, such as mucus plugs of cystic fibrosis patients, contaminated catheters, and contact lenses [5]. Biofilms, formed by some microorganisms, are complex communities covered by self-made exopolysaccharide (EPS) layers, which are irreversibly attached to these surfaces [6]. A mature biofilm has a suitable bacterial communication system inside the EPS layers. The mechanism of QS is directly involved with the formation of biofilms in different bacterial species, including P. aeruginosa [7,8]
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