Antibacterial effect of silver nanoparticles against Bacillus sp. under plasmon resonance condition

Background: According to the recent studies, the antibacterial activities of silver nanoparticles (Ag-NPs) were studied on Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. In this study antibacterial effect of silver nanoparticles that used for coating textiles, on E.coli and S.aureus was investigated. Methods: Silver nanoparticles were coated on textile fabric by corona treatment and the antibacterial properties of fabrics were quantitatively evaluated by using a Gram-positive bacterium S. aureus and Gram-negative bacterium E. coli. Results: The textiles coated with silver nanoparticles had favorable antimicrobial effect against both E. coli and S. aureus. The value of antibacterial activity was appropriated with corona power and deposition that was used for absorption of Silver nanoparticle on samples. Conclusions: These results suggest that silver nanoparticles could be used as an effective antibacterial material.

Circadian factors PER1, PER2, ARNTL and CLOCK are important molecular components of biological clock system and play a fundamental role in the metabolism at both the behavioral and molecular levels and potentially have great importance for understanding metabolic health and disease, because disturbance the circadian processes lead to developing of different pathology. The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronics, home products, and for water disinfection, but little is yet known about their toxicity. These nanoparticles induce blood-brain barrier destruction, astrocyte swelling, cause degeneration of neurons and impair neurodevelopment as well as embryonic development. We studied the expression of genes encoded the key molecular components of circadian clock system in different rat organs after intratracheally instilled silver nanoparticles which quite rapidly translocate from the lungs into the blood stream and accumulate in different tissues. We have shown that silver nanoparticles significantly affect the expression levels of PER1, PER2, ARNTL and CLOCK mRNA in different rat tissues in time-dependent and tissue-specific manner. High level of PER1, ARNTL and CLOCK mRNA expression was observed in the lung on the 1st 3rd and 14th day after treatment of rats with silver nanoparticles. At the same time, the expression level of PER1 mRNA in the brain and liver increases predominantly on the 1st and 14th day but decreases in the testis. Significant increase of the expression level of PER2 and ARNTL mRNA was detected only in the brain of treated by silver nanoparticles rats. Besides that, intratracheally instilled silver nanoparticles significantly reduced the expression levels of CLOCK mRNA in the brain, heart and kidney. No significant changes in the expression level of PER2 mRNA were found in the lung, liver, heart and testis, except kidney where this mRNA expression decreases on the 3rd and 14th day after treatment of rats with silver nanoparticles. It was also shown that expression level of PFKFB4, a key enzyme of glycolysis regulation, gradually reduces in the brain from 1st to 14th day being up to 4 fold less on 14th day after treatment of animals with silver nanoparticles. Thus, the intratracheally instilled silver nanoparticles significantly affect the expression of PER1, PER2, ARNTL, and CLOCK genes which are an important molecular component of circadian clock system. This is because a disruption of the circadian processes leads to a development of various pathologic processes. The results of this study clearly demonstrate that circadian genes could be a sensitive test for detection of silver nanoparticles toxic action and suggest that more caution is needed in biomedical applications of silver nanoparticles as well as higher level of safety in silver nanoparticles production industry.

Polyhexamethylene biguanide (PHMB), a broad spectrum disinfectant against many pathogens, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles. The particles formed were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering, electrophoretic mobility, and TEM to measure their morphology and surface chemistry. PHMB-functionalized silver nanoparticles were then evaluated for their antimicrobial activity against a gram-negative bacterial strain, Escherichia coli. These silver nanoparticles were found to have about 100 times higher bacteriostatic and bactericidal activities, compared to the previous reports, due to the combined antibacterial effect of silver nanoparticles and PHMB. In addition to other applications, PHMB-functionalized silver nanoparticles would be extremely useful in textile industry due to the strong interaction of PHMB with cellulose fabrics.

Objective: To evaluate the antimicrobial properties and dental pulp stem cells (DPSCs) cytotoxicity of synthesized carboxymethyl cellulose-silver nanoparticles impregnated on titanium plates. Material and methods: The antibacterial effect of silver nanoparticles in a carboxymethyl cellulose matrix impregnated on titanium plates (Ti-AgNPs) in three concentrations: 16%, 50% and 100% was determined by adding these to bacterial cultures of Streptococcus mutans and Porphyromonas gingivalis. The Ti-AgNPs cytotoxicity on DPSCs was determined using a fluorimetric cytotoxicity assay with 0.12% chlorhexidine as a positive control. Results: Silver nanoparticles in all concentrations were antimicrobial, with concentrations of 50% and 100% being more cytotoxic with 4% cell viability. Silver nanoparticles 16% had a cell viability of 95%, being less cytotoxic than 0.12% chlorhexidine. Conclusions: Silver nanoparticles are a promising structure because of their antimicrobial properties. These have high cell viability at a concentration of 16%, and are less toxic than chlorhexidine.

This study evaluates the antibacterial effect of silver nanoparticles against two clinically significant bacterial species: Escherichia coli and Klebsiella pneumoniae. Bacterial isolates are collected from AlShaheed Ghazi Al-Hariri Hospital for Specialized Surgeries in Baghdad, and activated using Brain Heart Infusion (BHI) broth. They are then cultured on MacConkey and Nutrient agar media. Both species have demonstrated lactose fermentation, as evidenced by the change in the MacConkey medium to a pink color. Silver nanoparticles are prepared in four concentrations (0.0100 g, 0.0150 g, 0.0200 g, and 0.0500 g) dissolved in 100 ml of dimethyl sulfoxide (DMSO), and their antibacterial activity is tested by using the well diffusion method. After 24 hours of incubation, E. coli has showed a clear inhibition zone of 4 cm at the highest concentration, indicating strong sensitivity to the nanoparticles. In contrast, K. pneumoniae has exhibited no inhibition zones at any concentration, suggesting resistance under the same conditions. These findings highlight the species-specific antibacterial activity of silver nanoparticles. The effective inhibition observed against E. coli but not against K. pneumoniae emphasizes the need for further research to optimize nanoparticle formulations or to explore their combined use with antibiotics to enhance antimicrobial efficacy.

Antimicrobial/antifungal effects of silver nanoparticles obtained with a novel electrochemical method on <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Escherichia</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coli</i> , <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Staphylococcus</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">aureus</i> , <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Aspergillus</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">niger</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Penicillium</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">phoeniceum</i> cultures have been studied. The tests conducted have demonstrated that synthesized silver nanoparticles - when added to water paints or cotton fabrics - show a pronounced antibacterial/antifungal effect.

The growing challenge posed by antimicrobial resistance (AMR) has prompted the exploration of innovative approaches to combat bacterial infections. Among these, long-chain fatty acids (LCFAs) and liposomes loaded with LCFAs (LipoFAs) have emerged as promising contenders against AMR. However, existing research primarily focuses on evaluating their antibacterial impacts on bacteria using biological methods. The design of these agents often relies on traditional assay methods that fail to accurately replicate the complexity of bacterial membranes, including the presence of charged phospholipids, nanometer dimensions, and other intricacies within the bacterial membranes. While it is known that LCFAs and LipoFAs exhibit membrane-active modes of action against the bacterial membranes, the detailed mechanisms of their interactions with membranes remain unclear. Herein, the development of a systematic analytical framework using supported lipid bilayer (SLB) platforms was reported to investigate how LCFAs, specifically linolenic acid (LNA), linoleic acid (LLA), and oleic acid (OA), and LipoFAs, including LNA-loaded liposomes (lipoLNA), LLA-loaded liposomes (LipoLLA), and OA-loaded liposomes (LipoOA), interact with model membrane systems. The central hypothesis of this thesis posits that SLBs can serve as predictive models for determining the antimicrobial efficacy and mechanisms of action (MOA) of LCFAs and LipoFAs. To test this hypothesis, single-component and multi-component SLBs, designed to closely mimic the composition and structure of bacterial membranes, were fabricated to study membrane interactions. Biophysical experimental findings revealed that LCFAs induce tubular formations and exhibit critical micelle concentration (CMC)-dependent membrane-disruptive behavior on single-component SLBs. Additionally, LNA and LLA exhibited interaction behaviors correlated with the CMC on multi-component bacterial membrane SLBs, leading to membrane remodeling and morphological changes at concentrations above CMC values. In contrast, OA exhibited CMC-independent activity, showing membrane insertion into the model membrane platform. LNA and LLA exhibited bactericidal effects, enhancing membrane permeability and ATP leakage, while OA, characterized by CMC-independent activity profile, exhibited potent bactericidal effects by penetrating the SLBs effectively, increasing membrane permeability and ATP leakage. The observed activities of LCFAs on S. aureus correlated with their behavior on Gram-positive bacterial model membranes, highlighting the significance of multiple-component model systems in understanding antimicrobial activity. The study also explored the mechanistic interactions between LipoFAs and model bacterial membranes, revealing that LipoLNA and LipoLLA, encapsulated with FAs with higher degrees of unsaturation, induced a curved membrane surface morphology due to higher curvature stress, potentially increasing membrane permeability and leakage of intracellular ATP. These changes correlated with stronger bacteriostatic and bactericidal effects on S. aureus MW2. Overall, this research contributes to the ongoing efforts to combat AMR by elucidating the efficacy of antimicrobial agents and highlights the potential of using biologically relevant model membrane systems to develop innovative strategies for designing effective therapeutic agents in healthcare and biotechnology.

The synthesis of silver nanoparticles and some metallic nano particles is emerging area of research in the field of science and technology due to their potential application especially in the field of biotechnology and biomedical sciences. In this study silver nano particles were synthesized from Penicillium madriti (MTCC2804) by extracellular method. The change in colour of the solution indicated the formation of nanoparticles. The nanoparticles were further confirmed by uv-vis spectrophotometry, Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM). The antibacterial activity of these nano particles were tested against various pathogenic bacteria like E coli, Staphylococcus auras, Klebsiella, Vibrio cholerae and Proteus vulgaris. After this these nanoparticles have been compared with ofloxacin and sparfloxacin.

A combined use of silver nanoparticles (AgNPs) with different types of disinfectants as antimicrobial might be useful in mitigating the problem of development of bacterial resistance with a strong enhancement of the biocidal effect of disinfectants. To evaluate the biocidal activity of silver nanoparticles and its loaded forms, five commercial disinfectants (quaternary ammonium compounds (benzalkonium chloride (BC) and TH4+), Virkon®S, sodium hypochlorite, and hydrogen peroxide (H2O2)) were used against Listeria monocytogenes (L. monocytogenes) isolates at different concentrations and exposure times to reveal intra-species variability and the percentage of resistance to antimicrobial agents used. Therefore, a total of 260 specimens from animal and human stool as well as environmental samples from dairy cattle farms were cultured for isolation of L. monocytogenes. Thereafter, bacterial isolates were identified using PCR. Silver nanoparticle was synthesized using chemical reduction. Both silver nanoparticles and its loaded forms were characterized by transmission electron microscopy (TEM). The sensitivity test of 60 strains of L. monocytogenes bacteria to AgNPs and its loaded forms was evaluated using broth macrodilution method. Virkon®S/AgNPs 2.0% exhibited the highest bactericidal effect (100%) against L. monocytogenes strains followed by H2O2/AgNPs 5.0% and TH4+/AgNPs 1.0% (90% each). Furthermore, the percentage of resistance of L. monocytogenes was 0.0% to both H2O2/AgNPs 5.0% and Virkon®S/AgNPs 2.0%. In conclusion, monitoring the main source of contamination with Listeria monocytogenes in dairy cattle farms is an essential factor to achieve an efficient control. Moreover, the use of the disinfectants, Virkon®S 2.0%, H2O2 5.0%, and TH4+1.0%, loaded on silver nanoparticles composite had the strong bactericidal effect against L. monocytogenes.

Silver nanoparticles are the most important nanoparticles in connection with the antimicrobial effect. Nowadays, the green synthesis of various types of nanoparticles is rapid, effective and produce less toxic nanoparticles often with specific properties. In our experiment we have developed and described in details various types of silver nanoparticles synthesized chemically or by the green synthesis. Nine different silver nanoparticles were synthesized, three by citrate method at different pHs (8; 9; 10), four using gallic acid at alkaline pHs (10; 11), and two by green synthesis using green tea and coffee extracts, both at pH 9. Characterisation of silver nanoparticles was performed using dynamic light scattering, scanning electron microscopy, and ultraviolet-visible absorption spectroscopy. Silver nanoparticles prepared by green synthesis showed the highest antioxidant activity and also ability for quenching of free radicals. Antibacterial activity of silver nanoparticles was determined on bacterial cultures such as Staphylococcus aureus and Escherichia coli. Silver nanoparticles synthesized using green tea and coffee extracts showed the highest antibacterial activity for both bacterial strains. Minimal inhibition concentration for both strains was found to be 65 μM at each silver nanoparticle synthesized using green synthesis.

The bactericidal action of silver (0) nanoparticles and amoxicillin on Escherichiacoli is studied, respectively. Increasing concentration of both amoxicillin(0–0.525 mg ml−1) and silvernanoparticles (0–40 µg ml−1) showed a higher antibacterial effect in Luria–Bertani (LB) medium. Escherichia colicells have different bactericidal sensitivity to them. When amoxicillin and silvernanoparticles are combined, it results in greater bactericidal efficiency on Escherichiacoli cells than when they were applied separately. Dynamic tests on bacterialgrowth indicated that exponential and stationary phases are greatly decreased anddelayed in the synergistic effect of amoxicillin and silver nanoparticles. In addition,the effect induced by a preincubation with silver nanoparticles is examined. Theresults show that solutions with more silver nanoparticles have better antimicrobialeffects. One hypothesized mechanism is proposed to explain this phenomenon.

In vitro and in vivo antibacterial activity of silver nanoparticles (AgNPs) against pathogenic bacteria has been demonstrated. Gram (+) and Gram (-) bacteria, including multidrug-resistant species, are susceptible to AgNPs' antibacterial effects. AgNPs have several concurrent mechanisms of action, and they work effectively with other antibacterial agents, such as antibiotics or chemical compounds, against infections like Esecheria coli and Staphylococcus aureus. Due to their unique characteristics, silver nanoparticles are perfect for use in healthcare and biomedical products where they can successfully treat or prevent infections. AgNPsʹ demonstrated genuine properties and significant potential for the development and improvement of novel antimicrobial agents, drug-delivery formulations, identification, detection, and diagnosis platforms, biomaterial and medical device coverings, tissue restoration and regeneration materials, complex healthcare condition schemes and strategies, and performance-enhanced therapeutic alternatives. The purpose of this review was to give a comprehensive discussion of the present state of the art in using the most relevant types of silver nanoparticles as antibacterial agents. This review aims to identify factors influencing the antibacterial impacts of silver nanoparticles and to highlight the benefits of using AgNPs as new antibacterial agents in addition to antibiotics, which will decrease the dosage necessary and avoid secondary effects combined with both. This is due to the need for new, effective, and efficient antibacterial agents.

Due to the wide applications of silver nanoparticles (AgNPs), research on their ecological synthesis has been extensive in recent years. In our study, biogenic silver nanoparticles were synthesized extracellularly using the white rot fungus Trametes versicolor via two cultivation methods: static and shaking. The cell filtrate of the fungus was used as a reducing agent in the process of nanoparticle synthesis. Characterization of the obtained nanoparticles was carried out using UV–VIS spectroscopy and scanning electron microscopy. The biosynthesized nanoparticles have antimicrobial potential against pathogenic bacteria, particularly in Gram-negative strains. The bactericidal effect was obtained for E. coli at a concentration of 7 µg/mL. The use of higher concentrations of compounds was necessary for Gram-positive bacteria. Taking into account the problem of the risk of cytotoxicity of AgNPs, combined therapy using a phytochemical was used for the first time, which was aimed at reducing the doses of nanoparticles. The most representative synergistic effect was observed in the treatment of 5 µg/mL silver nanoparticles in combination with 15 µg/mL ursolic acid against E. coli and P. aeruginosa with a bactericidal effect. Moreover, the coadministration of nanoparticles considerably reduced the growth of both Staphylococcus strains, with a bactericidal effect against S. aureus. The viability test confirmed the strong synergistic effect of both tested compounds. Silver nanoparticles synthesized using the T. versicolor showed excellent antibacterial potential, which opens perspectives for future investigations concerning the use of the nanoparticles as antimicrobials in the areas of health.

Research designed to prevent human beings from being infected by microorganisms such as bacteria, molds, yeasts, and viruses from the living environment has attracted tremendous interest. Therefore, many researchers have tried to develop novel and effective antimicrobial materials with free of resistance and low cost [1, 2]. One of the most widely used antibacterial materials is based on silver (silver ions or silver nanoparticles) which exhibits strong biocidal effects towards a broad range of microorganisms, along with advantages such as a lack of odor, taste, and color [3– 6]. Until now, various routes for preparing antimicrobial silver compounds or silver nanoparticles (NPs) have been reported [7, 8]. Especially, silver NPs have more severe effects on bacterial cells than silver ions [9]. However, silver NPs are easily aggregated which causes the deterioration of their chemical properties and decreases their antimicrobial properties. Moreover, the fate of silver NPs for biological applications is still debatable [10, 11]. In addition, some synthetic methods of silver NPs as antimicrobial materials are time-consuming and require expensive instruments. In addition, silver NPs can easily become aggregated, which causes the deterioration of their chemical properties and decreases their antimicrobial properties. To solve these problems, silver has been introduced onto stable supporting materials, in which the antimicrobial mechanism is closely related to the release of silver ions. These methods have several advantages, such as sustained antibacterial effects based on the release of silver ions, good mechanical properties and inexpensive and easy manufacturing processes for industrial applications [12–17]. Recently, many different methods have been proposed to introduce silver NPs into polymers. Among the various polymers, polystyrene (PS)–divinylbenzene (DVB) porous resin is particularly useful, due to its large surface area, chemical stability, and low cost. Moreover, silver NPs can be easily embedded on it after sulfonation, and their size and the loading amount can be adjusted by changing of reaction condition [18]. The deposition of silver on polymer materials has been enhanced by the activation of the surface-functional groups. Among the various functional groups, sulfonated groups are good candidates to introduce silver NPs for the purpose of producing antibacterial materials. Recently, we introduced silver NPs into sulfonated PS–DVB resins (4–8 lm) with mild reduction using the polyol method for use as surface-enhanced Raman scattering (SERS) active materials for multiplex protein analysis [18, 19]. In this study, silver NPs embedded into ion-exchange resin (Ag-IER) (ca. 0.9 mm) were readily prepared by the polyol method and characterized by several instrumental analyses, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray emission (EDX), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Then, their anti-bacterial activity was tested using Escherichia coli, which is well known as indicator bacteria. Moreover, we investigated their antibacterial effect at a low silver loading level and silver ion release conditions. B.-H. Jun J. Y. Kim H.-J. Park J. Yoon Y.-S. Lee (&) School of Chemical and Biological Engineering, Seoul National University, Seoul 151-747, Korea e-mail: yslee@snu.ac.kr

Silver nanoparticles (colloidal silver) have a bactericidal effect against a variety of bacteria, fungi and viruses. They are promising for biomedical applications due to the limited toxicity against eukaryotic cells. Important role in the silver nanoparticles production have various microorganisms including lactic acid bacteria of the genus Lactobacillus. Probiotic Lactobacillus species are good candidates for nanoparticles producing in the laboratory and in industrial scale, too. The aim of this work was to test the production of colloidal silver nanoparticles with probiotic species Lactobacillus casei. Nanoparticles production was tested in the reaction mixtures (phosphate buffer, glucose, bacterial cells) upon addition of varying concentrations of AgNO3 (1 - 4mM). Production of the silver nanoparticles was proven by screening of reaction mixtures by Transmission electron microscopy. Level of Ag+ ions utilization to nanoparticles was analysed by optical emission spectrometry. Results showed high efficiency of nanosilver production with narrow size distribution of nanoparticles (12 - 27nm).