Silver nanoparticles restrict microbial growth by promoting oxidative stress and DNA damage

Nanocomposites: silver nanoparticles and bacteriocins obtained from lactic acid bacteria against multidrug-resistant Escherichia coli and Staphylococcus aureus

Drug-resistant bacteria such as Escherichia coli and Staphylococcus aureus represent a global health problem that requires priority attention. Due to the current situation, there is an urgent need to develop new, more effective and safe antimicrobial agents. Biotechnological approaches can provide a possible alternative control through the production of new generation antimicrobial agents, such as silver nanoparticles (AgNPs) and bacteriocins. AgNPs stand out for their antimicrobial potential by employing several mechanisms of action that can act simultaneously on the target cell such as the production of reactive oxygen species and cell wall rupture. On the other hand, bacteriocins are natural peptides synthesized ribosomally that have antimicrobial activity and are produced, among others, by lactic acid bacteria (LAB), whose main mechanism of action is to produce pores at the level of the cell membrane of bacterial cells. However, these agents have disadvantages. Nanoparticles also have limitations such as the tendency to form aggregates, which decreases their antibacterial activity and possible cytotoxic effects, and bacteriocins have a narrow spectrum of action, require high doses to be effective, and can be degraded by proteases. Given these limitations, nanoconjugates of these two agents have been developed that can act synergistically in the control of pathogenic bacteria resistant to antibiotics. This review focuses on knowing relevant aspects of the antibiotic resistance of E. coli and S. aureus, the characteristics of these new generation antibacterial agents, and their effect alone or forming nanoconjugates that are more effective against the multiresistant mentioned bacteria.

Plackett-Burman screening of physico-chemical variables affecting Citrus peel-mediated synthesis of silver nanoparticles and their antimicrobial activity

With the growing resistance of pathogenic microbes to traditional drugs, biogenic silver nanoparticles (SNPs) have recently drawn attention as potent antimicrobial agents. In the present study, SNPs synthesized with the aid of orange (Citrus sinensis) peel were engineered by screening variables affecting their properties via Plackett-Burman design. Among the variables screened (temperature, pH, shaking speed, incubation time, peel extract concentration, AgNO3 concentration and extract/AgNO3 volume ratio), pH was the only variable with significant effect on SNPs synthesis. Therefore, SNPs properties could be enhanced to possess highly regular shape with zeta size of 11.44 nm and zeta potential of - 23.7 mV. SNPs purified, capped and stabilized by cloud point extraction technique were then checked for their antimicrobial activity against Bacillus cereus, Listeria innocua, Listeria monocytogenes, Staphylococcus aureus, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhimurium and Candida albicans. The maximum antimicrobial activity of SNPs was recorded against E. coli, L. monocytogenes and C. albicans with clear zone diameter of 33.2, 31.8 and 31.7 mm, respectively. Based on minimum inhibition concentration and minimum bactericidal concentration of SNPs (300 mg/l) as well as their effect on respiratory chain dehydrogenases, cellular sugar leakage, protein leakage and lipid peroxidation of microbial cells, E. coli was the most affected. Scanning electron microscopy, protein banding and DNA fragmentation proved obvious ultrastructural and molecular alterations of E. coli treated with SNPs. Thus, biogenic SNPs with enhanced properties can be synthesized with the aid of Citrus peel; and such engineered nanoparticles can be used as potent antimicrobial drug against E. coli.

Effect of membrane depolarization against Aspergillus niger GM31 resistant by ultra nanoclusters characterized by Ag2+ and Ag3+ oxidation state

To date, the impossibility of treating resistant forms of bacteria and fungi (AMR) with traditional drugs is a cause for global alarm. We have made the green synthesis of Argirium silver ultra nanoclusters (Argirium-SUNCs) very effective against resistant bacteria (< 1 ppm) and mature biofilm (0.6 ppm). In vitro and preclinical tests indicate that SUNCs are approximately 10 times less toxic in human cells than bacteria. Unique chemical-physical characteristics such as particle size < 2 nm, a core composed of Ag⁰, and a shell of Ag ⁺, Ag²⁺ , Ag³⁺ never observed before in stable form in ultra pure water, explain their remarkable redox properties Otto Cars (Lancet Glob. Health 9:6, 2021). Here we show that Argirium-SUNCs have strong antimicrobial properties also against resistant Aspergillus niger GM31 mycelia and spore inactivation (0.6 ppm). The membrane depolarization is a primary target leading to cell death as already observed in bacteria. Being effective against both bacteria and fungi Argirium-SUNCs represent a completely different tool for the treatment of infectious diseases.

Biogenic nanosilver bearing antimicrobial and antibiofilm activities and its potential for application in agriculture and industry

Introduction

Due to the increasing resistance of bacteria and fungi to antimicrobials, it is necessary to search for effective alternatives to prevent and treat pathogens causing diseases in humans, animals, and plants. In this context, the mycosynthesized silver nanoparticles (AgNPs) are considered as a potential tool to combat such pathogenic microorganisms.

Methods

AgNPs were synthesized from Fusarium culmorum strain JTW1 and characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Nanoparticle Tracking Analysis (NTA), Dynamic Light Scattering (DLS) and Zeta potential measurement. The minimum inhibitory (MIC) and biocidal concentrations (MBC) were determined against 13 bacterial strains. Moreover, the combined effect of AgNPs with antibiotics (streptomycin, kanamycin, ampicillin, tetracycline) was also studied by determining the Fractional Inhibitory Concentration (FIC) index. The anti-biofilm activity was examined by crystal violet and fluorescein diacetate (FDA) assays. Furthermore, antifungal activity of AgNPs was evaluated against a panel of phytopathogenic fungi viz., Botrytis, Colletotrichum, Fusarium, Phoma, Sclerotinia, and an oomycete pathogen Phytophthora by agar well-diffusion and micro-broth dilution method to evaluate the minimal AgNPs concentrations that inhibit fungal spore germination.

Results

Fungi-mediated synthesis resulted in the formation of small (15.56 ± 9.22 nm), spherical and stable (zeta potential of - 38.43 mV) AgNPs with good crystallinity. The results of FTIR spectroscopy indicated the presence of various functional groups, namely hydroxyl, amino, and carboxyl ones, from the biomolecules on the surface of AgNPs. The AgNPs showed antimicrobial and antibiofilm formation activities against Gram-positive and Gram-negative bacteria. The values of MIC and MBC ranged between 16-64 and 32-512 μg mL^-1, respectively. The enhanced effect of AgNPs in combination with antibiotics was confirmed against human pathogens. The highest synergistic effect (FIC = 0.0625) was demonstrated by the combination of AgNPs with streptomycin against two strains of Escherichia coli (ATCC 25922 and ATCC 8739), followed by Klebsiella pneumoniae and Pseudomonas aeruginosa (FIC = 0.125). Enhanced effects of AgNPs with ampicillin were also shown against Staphylococcus aureus ATCC 25923 (FIC = 0.125) and P. aeruginosa (FIC = 0.25), as well as kanamycin against S. aureus ATCC 6538 (FIC = 0.25). The crystal violet assay revealed that the lowest concentration of AgNPs (0.125 μg mL^-1) reduced the development of biofilms of Listeria monocytogenes and Salmonella enterica, while the maximum resistance was shown by Salmonella infantis, its biofilm was reduced after exposure to a concentration of 512 μg mL^-1. A high inhibitory effect on the activity of bacterial hydrolases was observed by the FDA assay. AgNPs at a concentration of 0.125 μg mL^-1 reduced the hydrolytic activity of all biofilms formed by the tested pathogens, except E. coli ATCC 25922, P. aeruginosa, and Pectobacterium carotovorum (efficient concentration was 2-fold higher, at 0.25 μg mL^-1), while the hydrolytic activity of E. coli ATCC 8739, Salmonella infantis and S. aureus ATCC 6538 was suppressed after treatment with AgNPs at concentrations of 0.5, 2 and 8 μg mL^-1, respectively. Moreover, AgNPs inhibited fungal growth and spore germination of Botrytis cinerea, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs against spores of these fungal strains were determined at 64, 256, and 32 μg mL^-1, and zones of growth inhibition were 4.93, 9.54, and 3.41 mm, respectively.

Discussion

Fusarium culmorum strain JTW1 was found to be an eco-friendly biological system for an easy, efficient and inexpensive synthesis of AgNPs. In our study, the mycosynthesised AgNPs demonstrated remarkable antimicrobial (antibacterial and antifungal) and antibiofilm activities against a wide range of human and plant pathogenic bacteria and fungi singly and in combination with antibiotics. These AgNPs could be applied in medicine, agriculture, and food industry to control such pathogens that cause numerous human diseases and crop losses. However, before using them extensive animal studies are required to evaluate the toxicity, if any.

Histological Injury to Rat Brain, Liver, and Kidneys by Gold Nanoparticles is Dose-Dependent

Gold nanoparticles (GNPs) possess various interesting plasmonic properties that can provide a variety of diagnostic and therapeutic functionalities for biomedical applications. Compared to other inorganic metal nanoparticles (NPs), GNPs are less toxic and more biocompatible. However, the in vivo toxicity of gold nanoparticles on humans can be significant due to the size effect. This work aims to study the effect of multiple doses of small-size (≈20 nm) GNPs on the vital organs of Wistar rats. The study includes the oxidative stress in vital organs (liver, brain, and kidney) caused by GNPs and histopathology analysis. The rats were given a single caudal injection of NPs dispersed in PBS at 25, 50, 100, and 250 mg/kg of body weight. After sacrifice, both plasma and organs were collected for the determination of oxidant/antioxidant markers and histological studies. Our data show the high sensitivity of oxidative stress parameters to the GNPs in the brain, liver, and kidneys. However, the response to this stress is different between the organs and depends upon the antioxidant defense, where GSH levels control the MDA and PCO levels. Histological alterations are mild at 25, 50, and 100 mg/kg but significant at higher concentrations of 250 mg/kg. Therefore, histological impairments are shown to be dependent on the dose of GNPs. The results contribute to the understanding of oxidative stress and cellular interaction induced by nanoparticles.

Nanocomposites of Graphene Oxide-Silver Nanoparticles for Enhanced Antibacterial Activity: Mechanism of Action and Medical Textiles Coating

The resistance of microorganisms to antibiotics is a crucial problem for which the application of nanomaterials is among a growing number of solutions. The aim of the study was to create a nanocomposite (composed of graphene oxide and silver nanoparticles) with a precise mode of antibacterial action: what enables textiles to be coated in order to exhibit antibacterial properties. A characterization of nanomaterials (silver nanoparticles and graphene oxide) by size distribution, zeta potential measurements, TEM visualization and FT-IR was performed. The biological studies of the nanocomposite and its components included the toxicity effect toward two pathogenic bacteria species, namely Pseudomonas aeruginosa and Staphylococcus aureus, interaction of nanomaterials with the outer layer of microorganisms, and the generation of reactive oxygen species and lipid peroxidation. Afterwards, antibacterial studies of the nanocomposite’s coated textiles (cotton, interlining fabric, polypropylene and silk) as well as studies of the general toxicity towards a chicken embryo chorioallantoic membrane model were conducted. The toxicity of the nanocomposite used was higher than its components applied separately (zones of growth inhibition for P. aeruginosa for the final selected concentrations were as follows: silver nanoparticles 21 ± 0.7 mm, graphene oxide 14 ± 1.9 mm and nanocomposite 23 ± 1.6 mm; and for S. aureus were: silver nanoparticles 27 ± 3.8 mm, graphene oxide 14 ± 2.1 mm, and nanocomposite 28 ± 0.4 mm. The viability of P. aeruginosa and S. aureus after treatment with selected GO-Ag decreased to 27% and 31%, respectively, compared to AgNPs, when the viability of both species was 31% and 34%, accordingly). The coated textiles showed encouraging antibacterial features without general toxicity towards the chicken embryo chorioallantoic membrane model. We demonstrated that graphene oxide might constitute a functional platform for silver nanoparticles, improving the antibacterial properties of bare silver. Due to the application of the nanocomposite, the textiles showed promising antibacterial features with a low general toxicity, thereby creating a wide possibility for them to be used in practice.

Current approaches for the exploration of antimicrobial activities of nanoparticles

Infectious diseases of bacterial and viral origins contribute to substantial mortality worldwide. Collaborative efforts have been underway between academia and the industry to develop technologies for a more effective treatment for such diseases. Due to their utility in various industrial applications, nanoparticles (NPs) offer promising potential as antimicrobial agents against bacterial and viral infections. NPs have been established to possess potent antimicrobial activities against various types of pathogens due to their unique characteristics and cell-damaging ability through several mechanisms. The recently accepted antimicrobial mechanisms possessed by NPs include metal ion release, oxidative stress induction, and non-oxidative mechanisms. Another merit of NPs lies in the low likelihood of the development of microbial tolerance towards NPs, given the multiple simultaneous mechanisms of action against the pathogens targeting numerous gene mutations in these pathogens. Moreover, NPs provide a fascinating opportunity to curb microbial growth before infections: this outstanding feature has led to their utilization as active antimicrobial agents in different industrial applications, e.g. the coating of medical devices, incorporation in food packaging, promoting wound healing and encapsulation with other potential materials for wastewater treatment. This review discusses the progress and achievements in the antimicrobial applications of NPs, factors contributing to their actions, mechanisms underlying their efficiency, and risks of their applications, including the antimicrobial action of metal nanoclusters (NCs). The review concludes with a discussion of the restrictions on present studies and future prospects of nanotechnology-based NPs development.

The use of antimicrobial-impregnated fabrics in health services: an integrative review

Objective:

to analyze evidence concerning the feasibility of antimicrobial-impregnated fabrics in preventing and controlling microbial transmission in health services.

Method:

an integrative review using the following databases: MEDLINE (via PubMed), Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, and Latin American and Caribbean Health Sciences Literature (LILACS), regardless of language and date of publication. Seven studies were included in the analysis to verify the types of fabrics and substances used to impregnate the fabrics, applicability in health services, and decrease in microbial load.

Results:

silver nanoparticles and copper oxide are the main antimicrobial substances used to impregnate the fabrics. The patients’ use of these fabrics, such as in bed and bath linens and clothing, was more effective in reducing antimicrobial load than in health workers’ uniforms.

Conclusion:

the use of these antimicrobial-impregnated textiles, especially by patients, is a viable alternative to prevent and control microbial transmission in health services. Implementing these fabrics in health workers’ uniforms requires further studies, however, to verify its effectiveness in decreasing microbial load in clinical practice.

Transformation of Biowaste for Medical Applications: Incorporation of Biologically Derived Silver Nanoparticles as Antimicrobial Coating

Nanobiotechnology has undoubtedly influenced major breakthroughs in medical sciences. Application of nanosized materials has made it possible for researchers to investigate a broad spectrum of treatments for diseases with minimally invasive procedures. Silver nanoparticles (AgNPs) have been a subject of investigation for numerous applications in agriculture, water treatment, biosensors, textiles, and the food industry as well as in the medical field, mainly due to their antimicrobial properties and nanoparticle nature. In general, AgNPs are known for their superior physical, chemical, and biological properties. The properties of AgNPs differ based on their methods of synthesis and to date, the biological method has been preferred because it is rapid, nontoxic, and can produce well-defined size and morphology under optimized conditions. Nevertheless, the common issue concerning biological or biobased production is its sustainability. Researchers have employed various strategies in addressing this shortcoming, such as recently testing agricultural biowastes such as fruit peels for the synthesis of AgNPs. The use of biowastes is definitely cost-effective and eco-friendly; moreover, it has been reported that the reduction process is simple and rapid with reasonably high yield. This review aims to address the developments in using fruit- and vegetable-based biowastes for biologically producing AgNPs to be applied as antimicrobial coatings in biomedical applications.

COVID-19 and a novel initiative to improve safety by 3D printing personal protective equipment parts from computed tomography

BACKGROUND

Powered air-purifying respirators are in short supply and can break down with extended use. Replacement parts can become hard to acquire. The aim of this study was to create an innovative quality improvement proof of concept using rapid prototyping.

METHODS

Here we report three cases of 3D printed powered air-purifying respirator parts. 3D printing was performed on all parts using fused deposition modeling with standard polylactic acid, in the same way that presurgical models would be created. Measurements using an electronic caliper as well as CT scans were used to compare an original part to its corresponding 3D printed parts for accuracy.

RESULTS

Electronic caliper and computed tomography measurements both showed accuracy consistant with current published norms.

CONCLUSIONS

Ultimately, there will be questions surrounding intellectual property, effectiveness and potential long-term safety for these types of 3D printed parts. Future research should look into the addition of specific nanoparticles from the position of cost, efficacy, safety and improved accuracy.

Quercetin Caused Redox Homeostasis Imbalance and Activated the Kynurenine Pathway (Running Title: Quercetin Caused Oxidative Stress)

The search for new and better antimicrobial therapy is a continuous effort. Quercetin is a polyphenol with promising antimicrobial properties. However, the understanding of its antimicrobial mechanism is limited. In this study, we investigated the biochemical mechanistic action of quercetin as an antibacterial compound. Isolates of Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, and Staphylococcus aureus were initially exposed to quercetin for antibacterial evaluation. Subsequently, S. aureus (Gram-positive) and E. coli (Gram-negative) cells were exposed to quercetin with or without ascorbic acid, and cells were harvested for selected biochemical assays. These assays included redox homeostasis (lipid peroxidation, total thiol, total antioxidant capacity), nitric oxide, and kynurenine concentration as well as DNA fragmentation. The results revealed that quercetin caused lipid peroxidation in the bacterial isolates. Lipid peroxidation may indicate ensuing oxidative stress resulting from quercetin treatment. Furthermore, tryptophan degradation to kynurenine was activated by quercetin in S. aureus but not in E. coli, suggesting that local L-tryptophan concentration might become limiting for bacterial growth. These findings, considered together, may indicate that quercetin restricts bacterial growth by promoting oxidative cellular stress, as well as by reducing the local L-tryptophan availability by activating the kynurenine pathway, thus contributing to our understanding of the molecular mechanism of the antimicrobial action of quercetin.

The Potential of Silver Nanoparticles for Antiviral and Antibacterial Applications: A Mechanism of Action

Rapid development of nanotechnology has been in high demand, especially for silver nanoparticles (AgNPs) since they have been proven to be useful in various fields such as medicine, textiles, and household appliances. AgNPs are very important because of their unique physicochemical and antimicrobial properties, with a myriad of activities that are applicable in various fields, including wound care management. This review aimed to elucidate the underlying mechanisms of AgNPs that are responsible for their antiviral properties and their antibacterial activity towards the microorganisms. AgNPs can be synthesized through three different methods-physical, chemical, and biological synthesis-as indicated in this review. The applications and limitations of the AgNPs such as their cytotoxicity towards humans and the environment, will be discussed. Based on the literature search obtained, the properties of AgNPs scrutinizing the antibacterial or antiviral effect shown different interaction towards bacteria which dependent on the synthesis processes followed by the morphological structure of AgNPs.

Chemo-Protective Potential of Cerium Oxide Nanoparticles against Fipronil-Induced Oxidative Stress, Apoptosis, Inflammation and Reproductive Dysfunction in Male White Albino Rats

Fipronil (FIP) is an insecticide commonly used in many fields, such as agriculture, veterinary medicine, and public health, and recently it has been proposed as a potential endocrine disrupter. The purpose of this study was to inspect the reproductive impacts of FIP and the possible protective effects of cerium nanoparticles (CeNPs) on male albino rats. Rats received FIP (5 mg/kg bwt; 1/20 LD₅₀), CeNPs (35 mg/kg bwt) and FIP+CeNPs per os daily for 28 days. Serum testosterone levels, testicular oxidative damage, histopathological and immunohistochemical changes were evaluated. FIP provoked testicular oxidative damage as indicated by decreased serum testosterone (≈60%) and superoxide dismutase (≈50%), glutathione peroxidase activity (≈46.67%) and increased malondialdehyde (≈116.67%) and nitric oxide (≈87.5%) levels in testicular tissues. Furthermore, FIP induced edematous changes and degeneration within the seminiferous tubules, hyperplasia, vacuolations, and apoptosis in the epididymides. In addition, FIP exposure upregulated interleukin-1β (IL-1β), nitric oxide synthase 2 (NOS), caspase-3 (Casp3) and downregulated the Burkitt-cell lymphomas (BCL-2), inhibin B proteins (IBP), and androgen receptor (Ar) mRNA expressions Casp3, nitric oxide synthase (iNOS), ionized calcium-binding adapter molecule 1(IBA1), and IL-1β immunoreactions were increased. Also, reduction of proliferating cell nuclear antigen (PCNA), mouse vasa homologue (MVH), and SOX9 protein reactions were reported. Interestingly, CeNPs diminished the harmful impacts of FIP on testicular tissue by decreasing lipid peroxidation, apoptosis and inflammation and increasing the antioxidant activities. The findings reported herein showed that the CeNPs might serve as a supposedly new and efficient protective agent toward reproductive toxicity caused by the FIP insecticide in white male rats.