Antibiofilm Activity Of Silver Nanoparticles Research Articles

In vitro evaluation of antimicrobial and antibiofilm potentials of silver nanoparticles biosynthesised by Streptomyces griseorubens

This study was performed to determine the antimicrobial and antibiofilm activities of silver nanoparticles (AgNPs) biosynthesised using Streptomyces griseorubens AU2 isolated from soil. The antimicrobial activity of the AgNPs was determined by agar well diffusion, disc diffusion and broth microdilution methods. Diameters of the zone of inhibition results clearly displayed that the microbially biosynthesised AgNPs have potent antimicrobial activity against Candida albicans, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of the nanoparticles that had been determined by broth microdilution method were found to be 20 and 50 µg/ml for C. albicans, B. subtilis and S. aureus; 10 and 20 µg/ml for E. coli and P. aeruginosa, respectively. For determining the effect of AgNPs on biofilm formation under in vitro conditions, MIC and subMICs were studied on P. aeruginosa and S. aureus biofilms by using microplate biofilm assay. Treatment of the AgNPs resulted in a decrease in the biofilm formation of S. aureus and P. aeruginosa as 26.52 and 25.50%, respectively. As a result of this study, it can be suggested that actinobacterially synthesised AgNPs have an effective potential to be used for pharmaceutical applications against multi-resistant microorganisms.

TTC- Based Test as an Efficient Method to Determine Antibiofilm Activity of Silver Nanoparticles

Among metal nanoparticles, silver nanoparticles are a widely used in various life sectors such as in biomedical applications, air and water purification, food production, cosmetics, garments and in various household products. There are several methods for production of silver nanoparticles. Generally, silver nanoparticles can be prepared by chemical methods such as chemical reduction and electrochemical techniques, physical methods, and biological methods such as the use of microorganisms. The biological route of synthesis provides a great diversity in choice for its raw materials such as bacteria, algae, fungi and plants. The aim of the study was to evaluate the tetrazolium/formazan test as a method to determine antibiofilm activity of biological synthetized silver nanoparticles. In this study Bacillus subtilis grown on brewery effluent and produced biosurfactant was used for silver nanoparticles (Ag-NPs) synthesis. The culture supernatants were used in synthesis of Ag-NPs. The formation of nanoparticles accompanied by colour changes of the used reaction system was confirmed by UV-vis spectroscopy. The bacteria isolated from the biofilm of water supply system were used in the evaluation of the antibiofilm activity of biologically synthetized Ag-NPs. To compare the results the commonly used crystal violet assay (CV) for biofilm analysis was applied.

Synergistic antibacterial and antibiofilm activity of silver nanoparticles biosynthesized by lignin-degrading fungus

The fabrication of silver nanoparticles (Ag-NPs) through green chemistry is an emerging area in the field of medical nanotechnology. Ag-NPs were fabricated by enzymatic reduction of AgNO3 using two lignin-degrading fungus Aspergillus flavus (AfAg-NPs) and Emericella nidulans (EnAg-NPs). The prepared Ag-NPs were characterized by different spectroscopic techniques. Antibacterial activity of prepared Ag-NPs was demonstrated against selected Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus) bacteria in the term of minimum bactericidal concentration (MBC) and susceptibility constant (Z). The synergistic antibacterial activity of Ag-NPs with four conventional antibiotics was also determined by the fractional inhibitory concentration index (FICI) using the checkerboard microdilution method. The antibiofilm potential of Ag-NPs was also tested. The plasmon surface resonance of biosynthesized Ag-NPs shows its characteristic peaks at UV and visible region (~450 and 280 nm). Fourier transform infrared spectrometer (FTIR) analysis confirms the nature of the capping agents as protein (enzyme) and indicates the role of protein (enzyme) in reduction of silver ions. The average particle size and charge of synthesized Ag-NPs was ~100 nm and ~−20 mV, respectively. X-ray diffraction (XRD) and TEM analysis confirmed the purity, shape, and size (quasi-spherical, hexagonal, and triangular) of Ag-NPs. Energy-dispersive X-ray spectroscopy (EDX) data validate the biological synthesis of Ag-NPs. Low MBC and high susceptibility constant indicate the high antimicrobial strength of biosynthesized Ag-NPs. The antibacterial analysis demonstrates the synergistic antimicrobial activity of Ag-NPs with antibiotics. This study also shows that biosynthesized Ag-NPs have ability to inhibit the biofilm formation by 80–90 %. The Aspergillus flavus and Emericella nidulans-mediated biosynthesized Ag-NPs have significant antimicrobial activity and demonstrate synergistic effect in combination with antibiotics. It suggests that nanoparticles can be effectively used in combination with antibiotics to improve the efficacy of antibiotics against pathogenic microbes. The substantial antibiofilm efficiency of biosynthesized Ag-NPs would also be helpful against sensitive and multidrug-resistant strains.

Enhanced antibacterial and anti-biofilm activities of silver nanoparticles against Gram-negative and Gram-positive bacteria.

Silver nanoparticles (AgNPs) have been used as antibacterial, antifungal, antiviral, anti-inflammtory, and antiangiogenic due to its unique properties such as physical, chemical, and biological properties. The present study was aimed to investigate antibacterial and anti-biofilm activities of silver nanoparticles alone and in combination with conventional antibiotics against various human pathogenic bacteria. Here, we show that a simple, reliable, cost effective and green method for the synthesis of AgNPs by treating silver ions with leaf extract of Allophylus cobbe. The A. cobbe-mediated synthesis of AgNPs (AgNPs) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the antibacterial and anti-biofilm activity of antibiotics or AgNPs, or combinations of AgNPs with an antibiotic was evaluated using a series of assays: such as in vitro killing assay, disc diffusion assay, biofilm inhibition, and reactive oxygen species generation in Pseudomonas aeruginosa, Shigella flexneri, Staphylococcus aureus, and Streptococcus pneumonia. The results suggest that, in combination with antibiotics, there were significant antimicrobial and anti-biofilm effects at lowest concentration of AgNPs using a novel plant extract of A. cobbe, otherwise sublethal concentrations of the antibiotics. The significant enhancing effects were observed for ampicillin and vancomycin against Gram-negative and Gram-positive bacteria, respectively. These data suggest that combining antibiotics and biogenic AgNPs can be used therapeutically for the treatment of infectious diseases caused by bacteria. This study presented evidence of antibacterial and anti-biofilm effects of A. cobbe-mediated synthesis of AgNPs and their enhanced capacity against various human pathogenic bacteria. These results suggest that AgNPs could be used as an adjuvant for the treatment of infectious diseases.

Anti-biofilm activity of silver nanoparticles against different microorganisms

Biofilms confer protection from adverse environmental conditions and can be reservoirs for pathogenic organisms and sources of disease outbreaks, especially in medical devices. The goal of this research was to evaluate the anti-biofilm activities of silver nanoparticles (AgNPs) against several microorganisms of clinical interest. The antimicrobial activity of AgNPs was tested within biofilms generated under static conditions and also under high fluid shears conditions using a bioreactor. A 4-log reduction in the number of colony-forming units of Pseudomonas aeruginosa was recorded under turbulent fluid conditions in the CDC reactor on exposure to 100 mg ml−1 of AgNPs. The antibacterial activity of AgNPs on various microbial strains grown on polycarbonate membranes is reported. In conclusion, AgNPs effectively prevent the formation of biofilms and kill bacteria in established biofilms, which suggests that AgNPs could be used for prevention and treatment of biofilm-related infections. Further research and development are necessary to translate this technology into therapeutic and preventive strategies.

Silver nanoparticles: influence of stabilizing agent and diameter on antifungal activity against Candida albicans and Candida glabrata biofilms

The purpose of this work was to evaluate the size-dependent antifungal activity of different silver nanoparticles (SN) colloidal suspensions against Candida albicans and Candida glabrata mature biofilms. The research presented herein used SN of three different average sizes (5, 10 and 60 nm), which were synthesized by the reduction of silver nitrate through sodium citrate and which were stabilized with ammonia or polyvinylpyrrolidone. Minimal inhibitory concentration (MIC) assays were performed using the microdilution methodology. The antibiofilm activity of SN was determined by total biomass quantification (by crystal violet staining) and colony forming units enumeration. MIC results showed that all SN colloidal suspensions were fungicidal against the tested strains at very low concentrations (0·4-3·3 μg ml(-1) ). With regard to biomass quantification, SN colloidal suspensions were very effective only against C. glabrata biofilms, achieving biomass reductions around 90% at a silver concentration of 108 μg ml(-1) . In general, all SN suspensions promoted significant log(10) reduction of the mean number of cultivable biofilm cells after exposure to silver concentrations at or higher than 108 μg ml(-1) . Moreover, the results showed that the particle size and the type of stabilizing agent used did not interfere in the antifungal activity of SN against Candida biofilms. This study suggests that SN have antifungal therapeutic potential, but further studies are still required namely regarding formulation and delivery means. SN may contribute to the development of new strategies for the improvement of oral health and quality of life particularly of the complete denture wearers.

Assessment of antibacterial activity of silver nanoparticles on Pseudomonas aeruginosa and its mechanism of action

Antimicrobial activity of silver nanoparticles is gaining importance due its broad spectrum of targets in cell compared to conventional antimicrobial agents. In this context, a UV photo-reduction method was used for the synthesis and the nanoparticles were characterized by UV–Visible spectroscopy, transmission electron microscopy, atomic force microscopy and thermogravimetric analysis techniques. The antibacterial activity of the synthesized silver nanoparticles was evaluated both in liquid and solid growth media employing various susceptibility assays on Pseudomonas aeruginosa, a ubiquitous bacterium. The dose dependent growth suppression by nanoparticles was studied with well diffusion method. By broth dilution method, the minimum inhibitory concentration (MIC) was found to be 2 μg/ml. It was observed that the bactericidal effect depends both on nanoparticle concentration and number of bacteria present. In our study, we could demonstrate the complete antibiofilm activity of silver nanoparticles at a concentration as low as 1 μg/ml. Our observations substantiated the association of reactive oxygen species and cell membrane damage in the antibacterial mechanism of silver nanoparticles. Our findings suggested that these nanoparticles can be exploited towards the development of potential antibacterial coatings for various biomedical and environmental applications.

Silver nanoparticles as an alternative strategy against bacterial biofilms.

Biofilms are complex bacterial communities that resist the action of antibiotics and the human immune system. Bacteria within biofilms are the cause of numerous, almost impossible to eradicate, persistent infections. Biofilms can form on many medical devices and implants, and so have an enormous impact on medicine. Due to the lack of effective anti-biofilm antibiotics, novel alternative compounds or strategies are urgently required. This review describes some of the latest approaches in the field of biofilm treatment. New anti-biofilm technologies target different stages in the biofilm formation process. Some act to modify the colonized biomaterials to make them resistant to biofilm formation. One potentially important candidate treatment uses silver nanoparticles that show anti-bacterial and anti-biofilm activity. The biological action of nano-silver is complex and seems to involve a number of pathways. However, there have been few reports on the anti-biofilm activity of silver nanoparticles and the precise mechanism underlying their action remains unresolved. Here, we describe some anti-biofilm approaches employing AgNPs and consider the challenges and problems that need to be addressed in order to make silver nanoparticles a part of an effective anti-biofilm strategy.