Browsing by Author "Peiris, M. M. K."

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Bacterial enzyme-mediated synthesis of silver nanoparticles and antimicrobial activity
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Peiris, M. M. K.; Gunasekara, T. D. C. P.; Jayaweera, P. M.; Fernando, S. S. N.
Extracellular synthesis of silver nanoparticles (AgNPs) using bacteria has been explored for their unique physicochemical properties. Studies have shown that nitrate reductase enzyme catalyzes the bioreduction of Ag+ to Ag0 and formation of AgNPs. The objective of this study was to detect the presence/absence of nitrate reductase enzyme in selected bacteria and to study the formation of AgNPs. The antimicrobial activity of the biosynthesized AgNPs was also examined. Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Acinetobacter baumannii (confirmed clinical strain) and Staphylococcus aureus ATCC 25923 were cultured in Nutrient broth. After 72 h of incubation, AgNO3 was added into the culture supernatant. AgNP formation was confirmed by Energy Dispersive X-ray analysis (EDX) and Transmission Electron Microscopy (TEM). For the nitrate reductase assay, heavy inocula of the above selected bacteria were inoculated in Nitrate broth and incubated at 37°C for 24 h. One dropper full of sulfanilic acid and α-naphthylamine were added to each tube and the colour change was observed. If no color change was observed a small amount of zinc (Zn) powder was added and the color change was observed. Well-diffusion method was performed to study the antimicrobial activity of the synthesized AgNPs against E. coli ATCC 25922, S. aureus ATCC 25923, P. aeruginosa ATCC 27853, Candida albicans ATCC 10231 and selected clinical isolates of P. aeruginosa, S. aureus and C. albicans. Positive controls were 0.5% AgNO3 and chemically synthesized AgNPs (0.436 mg/ml). All biosynthesized AgNPs were spherical in shape. The average sizes of the NPs were 11.14 ± 6.59 nm (S. aureus-NPs 0.435 mg/ml), 11.71 ± 2.73 nm (P. aeruginosa-NPs 0.45 mg/ml), 12.87 ± 2.95 nm (E. coli-NPs 0.99 mg/ml) and 12.22 ± 2.45 nm (A. baumannii-NPs 0.665 mg/ml). In general, zones of inhibition (ZOIs) given for chemically synthesized AgNPs, were higher than biosynthesized NPs. According to the well diffusion results, AgNPs produced by S. aureus resulted in the largest ZOI against the selected pathogens. Biosynthesized AgNPs were highly effective against Gram negative bacteria compared to Gram positive bacterial and fungal species, as well as Candida albicans, which were opportunistic pathogens. A. baumannii, E. coli and S.aureus, except P. aeruginosa, gave red colour after adding the two reagents and when Zn dust was added to P. aeruginosa, no colour change was observed. AgNP synthesis with a narrow size distribution was observed for all tested bacterial strains. AgNPs of S. aureus gave highest ZOI. Nitrate reduction was observed with all organisms. Further characterization of NPs is required to study the physical properties of silver NPs
Biosynthesis of silver nanoparticles using Camonea bifida leaf extract and investigation of antimicrobial properties
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayawardena, Y. R.; Senevirathna, J. Y.; Peiris, M. M. K.
Silver nanoparticles (AgNPs) have been used in nanomedicine as an alternative antimicrobial agent and disinfectant. The biological synthesis of silver nanoparticles has gained much attention due to its eco-friendly and less toxic nature. The present study was focused on the biosynthesis of AgNPs using Camonea bifida leaf extract and the investigation of their antimicrobial and antibiofilm properties. Aqueous leaf extract (5 g/100 mL) of Camonea bifida was subjected to heat treatment at 60􀁱C. For the optimization of synthesis, parameters including AgNO3 concentration, AgNO3: plant extract ratio, and reaction temperature were studied. The formation of AgNPs was confirmed by the UV-Visible absorption spectrum. Particle characterization was performed using Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and stability study. Antimicrobial activity was studied using well diffusion method against Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 1706), Candida glabrata (ATCC 90030), Candida albicans (ATCC 10231), and Candida tropicalis (ATCC 13803). Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were performed for Staphylococcus aureus and Pseudomonas aeruginosa. Gentamicin (600 μg/mL) and Fluconazole (500 μg/mL) were used as positive controls. The antibiofilm activity of AgNPs against Pseudomonas aeruginosa and Candida glabrata was performed using crystal violet assay. Color change and UV-Visible peak around 450 nm confirmed the formation of AgNPs. FT-IR spectrum indicated the presence of different functional groups of biomolecules such as O-H, C-H, C=O, C-N on the surface of AgNPs. The phytochemical analysis confirmed the presence of flavonoids, phenols, tannins, terpenoids, and chalcones as reducing and capping agents. TEM and SEM results indicated spherical-shaped AgNPs with an average size of 34 nm. AgNPs were stable for more than 4 weeks under room conditions. Pseudomonas aeruginosa (15.0±0.0 mm) and Staphylococcus aureus (16.0±0.6 mm) showed the highest sensitivity towards AgNPs while Escherichia coli showed moderate results (12.7±0.9 mm). Klebsiella pneumoniae and other Candida species did not respond except Candida tropicalis (10.3±0.3 mm). MIC and MBC of AgNPs against Staphylococcus aureus were 20.6 μg/mL and 41.3 μg/mL. MIC and MBC of AgNPs against Pseudomonas aeruginosa were 5.2 μg/mL and 10.3 μg/mL respectively. The percentage inhibition of biofilm formation of Pseudomonas aeruginosa and Candida glabrata was 69% and 61% respectively for 650 μg/mL AgNPs concentration. The overall results indicated the potential of using Camonea bifida mediated AgNPs as a promising antimicrobial and antibiofilm agent.
TiO2 nanoparticles from bakers’ yeast: a potent antimicrobial
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Peiris, M. M. K.; Gunasekara, T. D. C. P.; Jayaweera, P. M.; Fernando, S. S. N.
Titanium dioxide (TiO2) is commonly applied in food industry, cosmetics and pharmaceuticals due to its photocatalytic activity, stability, optical and electronic properties and biocidal activity. TiO2 nanoparticles (NPs) can be synthesized by conventional chemical, physical and biological methods. In this study, TiO2 NPs were biosynthesized using Baker’s yeast (Y-TiO2) and characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray analysis (EDX). Antimicrobial activity was studied using plate coating method with and without sunlight exposure. XRD pattern confirmed the formation of pure anatase TiO2 nanoparticles. The porous surface of yeast cells act as the site for Ti3+ nucleation. According to EDX data, Ti (Atomic percentage of 20.89%), O (70.95%), P (5.78%) and N (2.38%) were the key elements in the sample. TEM imaging revealed that the nanoparticles were spherical with an average size of 6.7 ± 2.2 nm. The photocatalytic activity of TiO2 NPs was studied by monitoring the degradation of Methylene blue dye. Fifty percent of dye degradation was observed within 15 min of UV exposure. This study is the first report on antimicrobial study of yeastmediated TiO2 NPs synthesized using TiCl3. Antimicrobial activity of TiO2 nanoparticles was high against selected Gram positive bacteria and Candida albicans compared to Gram negative bacteria in the presence or absence of exposure to sunlight. The percentage reduction of colony forming units (CFU/mL) after exposure to Y-TiO2 NPs following 30 min of sunlight exposure significantly reduced S . aureus ATCC 25923 (77%), MRSA clinical isolate (97%) and C . albicans ATCC 10231 (95%) compared to the control due to the photocatalytic activity. The percentage reduction of CFU/mL for gram negative bacteria P . aeruginosa ATCC 27853, E . coli ATCC 25922 and A . baumannii clinical isolate were 58%, 46% and 50% respectively after exposure to sunlight. Y-TiO2 NPs showed antimicrobial activity in the absence of exposure to sunlight under room conditions. After 30 min of contact with Y-TiO2 NPs, percentage inhibition of S . aureus (20%), MRSA (25%), C . albicans (74%), P . aeruginosa (30%), E . coli (26 %) and A . baumannii (23%) were lower compared to sunlight exposure. Sunlight exposure has enhanced antimicrobial activity of TiO2 NPs. The outcomes indicate the significant physical properties and the impact of yeast-mediated TiO2 nanoparticles as a novel antimicrobial.
Zinc oxide nanoparticles synthesized using Camonea bifida leaf extract as a potential antimicrobial and antibiofilm agent
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayalath, C. N.; Kaluarachchi, D. U.; Peiris, M. M. K.
Metal nanoparticles have gained much attention in the biomedical field due to excellent biocompatibility and less toxicity. Zinc oxide nanoparticles (ZnO NPs) have exhibited excellent therapeutic value by acting antimicrobial, anti-cancer, anti-diabetic and anti-inflammatory agent. ZnO NPs are also effective in combating biofilm-associated infections. Only a few investigations have been performed on NP synthesis using C. bifida. This study was conducted to evaluate the in vitro antibiofilm and antimicrobial activity of Camonea bifida-derived ZnO NPs. C. bifida leaf extract was prepared by boiling 2g of dried leaves powder in 40 ml of distilled water at 60oC for 30 minutes. ZnO nanoparticles were synthesized using (Zn(CH3CO2)2) as the reducing agent for Zinc ions. The effect of reaction parameters including zinc acetate (Zn(CH3CO2)2) concentration, leaf extract: Zn(CH3CO2)2 ratio and reaction temperature were optimized to achieve higher yield using UV-Visible spectroscopy ((Zn(CH3CO2)2 concentration: 0.1-0.5 M), leaf extract: Zn(CH3CO2)2 ratio 1:9, 1:7, 1:5, 1:3, 1:1 and reaction temperature : 0oC, 30oC, 40oC, 60oC, 80oC). Nanoparticles were characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy (FT-IR). The antimicrobial activity of ZnO NPs was studied against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 1706), Pseudomonas aeruginosa (ATCC 27853), Candida albicans (ATCC 10231), Candida glabrata (ATCC 90030), Candida tropicalis (ATCC 13803). Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were studied. Gentamicin (600μg/mL) and Fluconazole (500μg/mL) were the positive controls for bacteria and fungi respectively. Negative control was sterile distilled water. Antibiofilm activity of ZnO NPs was assessed using crystal violet assay for P. aeruginosa and C. glabrata. The optimum conditions were 0.3M Zn(CH3CO2)2, 1:3 ratio and 40℃. UV-Visible peak around 390 nm and precipitate formation confirmed the ZnO NP formation. ZnO NPs were spherical and irregularly shaped and were in the range of 60-70 nm. Functional groups attached on to the surface of NPs such as -OH and -C-H were revealed by FT-IR spectrum. According to UV-Visible spectra, ZnO NPs were stable for 2 months. All selected organisms were susceptible to ZnO NPs. Higher zones of inhibition were given by P. aeruginosa (30.7±0.3 mm), S. aureus (25.7±0.3 mm) and among fungi, C. tropicalis (27.7±0.3 mm). Both the MIC and MBC of ZnO NPs against S. aureus and P. aeruginosa were 3.6 mg/mL. ZnO NPs inhibited the biofilm formation of P. aeruginosa and C. glabrata by 68% and 52% respectively at 28.4 mg/mL concentration. S. aureus, P. aeruginosa and C. tropicalis showed higher susceptibility against the NPs. The highest antibiofilm activity of ZnO NPs was reported against P. aeruginosa. Results suggest that ZnO NPs are an effective antimicrobial and antibiofilm agent against tested pathogenic microorganisms.