Biosynthesized silver nanoparticles: are they effective antimicrobials?

A Novel Ag@AgCl Nanoparticle Synthesized by Arctic Marine Bacterium: Characterization, Activity and Mechanism

An additive- and pollution-free method for the preparation of biogenic silver and silver chloride nanoparticles (Ag@AgCl NPs) was developed from the bacteria Shewanella sp. Arc9-LZ, which was isolated from the deep sea of the Arctic Ocean. The optimal synthesizing conditions were explored, including light, pH, Ag⁺ concentration and time. The nanoparticles were studied by means of ultraviolet-visible (UV-Vis) spectrophotometry, energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometers (ICP-OES). The transmission electron microscope (TEM) showed that the nanoparticles were spherical and well dispersed, with particle sizes less than 20.00 nm. With Ag@AgCl nanoparticles, the kinetic rate constants for congo red (CR) and rhodamine B (RhB) dye degradation were 2.74 × 10^-1 min^-1 and 7.78 × 10^-1 min^-1, respectively. The maximum decolourization efficiencies of CR and RhB were 93.36% and 99.52%, respectively. Ag@AgCl nanoparticles also showed high antibacterial activities against the Gram-positive and Gram-negative bacteria. The Fourier transform infrared spectroscopy (FTIR) spectrum indicated that the O-H, N-H and -COO- groups in the supernatant of Arc9-LZ might participate in the reduction, stabilization and capping of nanoparticles. We mapped the schematic diagram on possible mechanisms for synthesizing Ag@AgCl NPs.

Investigation into the Antibacterial Mechanism of Biogenic Tellurium Nanoparticles and Precursor Tellurite

Antibacterial tellurium nanoparticles have the advantages of high activity and biocompatibility. Microbial synthesis of Te nanoparticles is not only a green technology but builds new ecological relationships in diverse environments. However, the antibacterial mechanism of Te nanoparticles is largely unclear. In this study, we report the bacterial synthesis of rod-shaped Te nanoparticles (BioTe) with high antibacterial activity against Escherichia coli. Morphology and permeability examination indicates that membrane damage is the primary reason for the antibacterial activity of BioTe, rather than ROS production and DNA damage. Moreover, a comparison of transcriptome and relative phenotypes reveals the difference in antibacterial mechanisms between BioTe and tellurite. Based on our evidence, we propose an antibacterial mode of rod-shaped BioTe, in which positively charged BioTe interact with the cell membrane through electrostatic attraction and then penetrate the membrane by using their sharp ends. In contrast, tellurite toxicity might be involved in sulfur metabolism.

Microbe-fabricated nanoparticles as potent biomaterials for efficient food preservation

In recent years, cutting-edge nanotechnology research has revolutionized several facets of the food business, including food processing, packaging, transportation, preservation, and functioning. Nanotechnology has beginning to loom large in the food business as the industry's demand for biogenic nanomaterial grows. The intracellular and extracellular synthesis of metal, metal oxide, and other essential NPs has recently been explored in a variety of microorganisms, including bacteria, actinomycetes, fungi, yeasts, microalgae, and viruses. These microbes produce a variety extracellular material, exopolysaccharides, enzymes, and secondary metabolites which play key roles in synthesizing as well as stabilizing the nanoparticle (NPs). Furthermore, genetic engineering techniques can help them to improve their capacity to generate NPs more efficiently. As a result, using microorganisms to manufacture NPs is unique and has a promising future. Microbial-mediated synthesis of NPs has lately been popular as a more environmentally friendly alternative to physical and chemical methods of nanomaterial synthesis, which require higher prices, more energy consumption, and more complex reaction conditions, as well as a potentially dangerous environmental impact. It is critical to consider regulatory measures implemented at all stages of the process, from production through refining, packaging, preservation, and storage, when producing bionanomaterials derived from culturable microbes for efficient food preservation. The current review discusses the synthesis, mechanism of action, and possible food preservation uses of microbial mediated NPs, which can assist to minimize food deterioration from the inside out while also ensuring that food is safe and free of contaminants. Despite the numerous benefits, there are looming debates concerning their usage in food items, particularly regarding its aggregation in human bodies and other risks to the environment. Other applications and impacts of these microbe-fabricated NPs in the context of future food preservation prospects connected with regulatory problems and potential hazards are highlighted.

Facile Green Synthesis of Silver Nanoparticles Using Aqueous Leaf Extract of Origanum majorana with Potential Bioactivity against Multidrug Resistant Bacterial Strains

The high prevalence of nosocomial bacterial resistance contributes to significant mortality and morbidity around the world; thus, finding novel antibacterial agents is of vital concern. Accordingly, the present study attempted to synthesize silver nanoparticles (AgNPs) using a green approach. Aqueous leaf extract of Origanum majorana was used to synthesize AgNPs and the antibacterial efficiency against multidrug resistant bacterial strains was detected. Characterization of the biogenic AgNPs was performed using ultraviolet-visible spectrophotometry (UV-Vis), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis, and X-ray diffraction analysis (XRD). The disc diffusion method was used to detect the antibacterial activity of AgNPs against three nosocomial multidrug-resistant strains. Preliminary UV-Vis analysis revealed the biosynthesis of AgNPs due to peak formation at 374 nm, corresponding to the surface plasmon resonance (SPR) of biogenic AgNPs. TEM micrographs detected the synthesis of small AgNPs with an average particle size of 26.63 nm. EDX analysis revealed the presence of the following elements: oxygen (3.69%), carbon (2.93%), aluminum (1.29), silicon (2.83%), chloride (17.89%), and silver (71.37%). Furthermore, XRD analysis revealed the presence of diffraction peaks at 2 theta (θ) degrees of 38.18°, 44.36°, 64.35°, and 77.54°, assigned to the planes of silver crystals (111), (200), (220), and (311), respectively. Collectively, these findings affirm the synthesis of biogenic AgNPs with potential physicochemical characteristics. The antimicrobial efficiency of the biogenic AgNPs indicated that Klebsiella pneumoniae strain was the most susceptible strain at concentrations of 50 and 100 µg/disk, with inhibitory zones of 21.57 and 24.56 mm, respectively. The minimum inhibitory concentration (MIC) of AgNPs against Klebsiella pneumoniae strain was found to be 10 µg/mL, while the minimum bactericidal concentration (MBC) was found to be 20 µg/mL. In conclusion, aqueous leaf extract of O. majorana mediated synthesis of small sized AgNPs, with potential antimicrobial effectiveness against multidrug-resistant bacterial pathogens.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

Silver nanoparticles from residual biomass: Biosynthesis, characterization and antimicrobial activity

The industrial effluent contaminated with organic pollutants has been causing an increase in the toxicity of the ecosystem, causing a great environmental impact. Thus, the present work aims the green synthesis of silver nanoparticles (AgNPs) from Aloe vera, its characterization and antimicrobial activity against Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 25923). AgNPs were characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Zeta Potential (ZP) and N₂ porosimetry (BET/BJH method). Antimicrobial activity were carried out by Minimal Inhibitory Concentration (MIC) method. The XRD demonstrated characteristic peaks of AgNPs at 38.29°; 44.55° and 64.81°, and SEM-EDS micrographs showed that AgNPs produced by biomolecules of Aloe vera extract resulted in a weight concentration around 92.59% silver, 7.15% oxygen and 0.26% chlorine. Regarding zeta potential, all samples showed negative electric charge (around -35.3 mV), while N₂ porosimetry resulted in a surface specific area of 6.09 m² g^-1, with a volume and diameter pore of 0.032 cm³ g^-1 and 33.47, respectively. Antimicrobial activity was observed at 15.62 µg mL^-1 and 31.25 µg mL^-1 for P. aeruginosa and S. aureus, respectively. Thus, AgNPs can be considered a promising nanoparticle for degradation of organic pollutants in aqueous solution as well as an adjuvant for treatment of microbial infections.

Biosynthesis of silver nanoparticles using Haloferax sp. NRS1: image analysis, characterization, in vitro thrombolysis and cytotoxicity

Haloferax sp strain NRS1 (MT967913) was isolated from a solar saltern on the southern coast of the Red Sea, Jeddah, Saudi Arabia. The present study was designed for estimate the potential capacity of the Haloferax sp strain NRS1 to synthesize (silver nanoparticles) AgNPs. Biological activities such as thrombolysis and cytotoxicity of biosynthesized AgNPs were evaluated. The characterization of silver nanoparticles biosynthesized by Haloferax sp (Hfx-AgNPs) was analyzed using UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The dark brown color of the Hfx-AgNPs colloidal showed maximum absorbance at 458 nm. TEM image analysis revealed that the shape of the Hfx-AgNPs was spherical and a size range was 5.77- 73.14 nm. The XRD spectra showed a crystallographic plane of silver nanoparticles, with a crystalline size of 29.28 nm. The prominent FTIR peaks obtained at 3281, 1644 and 1250 cm^{- 1} identified the Functional groups involved in the reduction of silver ion reduction to AgNPs. Zeta potential results revealed a negative surface charge and stability of Hfx-AgNPs. Colloidal solution of Hfx-AgNPs with concentrations ranging from 3.125 to 100 μg/mL was used to determine its hemolytic activity. Less than 12.5 μg/mL of tested agent showed no hemolysis with high significant decrease compared with positive control, which confirms that Hfx-AgNPs are considered non-hemolytic (non-toxic) agents according to the ISO/TR 7405-1984(f) protocol. Thrombolysis activity of Hfx-AgNPs was observed in a concentration-dependent manner. Further, Hfx-AgNPs may be considered a promising lead compound for the pharmacological industry.

Antimicrobial activity of camphor tree silver nano-particles against foulbrood diseases and finding out new strain of Serratia marcescens via DGGE-PCR, as a secondary infection on honeybee larvae

American foulbrood (AFB) and European foulbrood (EFB) are the two major bacterial diseases affecting honeybees, leading to a decrease in viability of the hive, decreasing honey production, and resulting in significant economic losses to beekeepers. Due to the inefficiency and/or low efficacy of some antibiotics, researches with nanotechnology represent, possibly, new therapeutic strategies. Nanostructure drugs have presented some advantagesover the conventional medicines, such as slow, gradual and controlled release, increased bioavailability, and reduced side-effects. In this study, different infected larvae were collected from two apiaries; the combs that had symptoms of American and European foulbrood were isolated. In vitro antimicrobial activity of camphor tree silver nano-particles against foulbrood diseases were characterized using UV-Vis spectrophotometry and scanning electron microscope (SEM) that proves the formation of silver nanoparticles with size range 160-660 nm. The antimicrobial activity of the silver nanoparticles was tested using agar diffusion assay and proved their ability to effectively cease the pathogenic bacterial growth in both AFB and EFB. DGGE-PCR technique has been applied for the identification of un-common bacterial infections honeybees depending on 16S rRNA amplification from their total extracted DNA and has been identified as Serratia marcescens (TES), deposited in GenBank with a new accession number (MT240613). The results were confirmed strain has been detected by DGGE-PCR analysis causing uniquely infected brood that was attacked by the American Foulbrood It could be concluded that greenly synthesized silver nanoparticles is projected to be used as effective treatment for honeybee bacterial diseases. These material need more investigations under field conditions and study the possibility of its residues in honeybee products such as honey, and beeswax.

Silver bionanoparticles toxicity in trophoblast is mediated by nitric oxide and glutathione pathways

Silver bionanoparticles (AgNPs) biosynthesized by Pseudomonas aeruginosa culture supernatant have an important antibacterial activity mediated by ROS increase; however their toxicity in human cells is not known. Due to the high susceptibility of the developing tissues to xenobiotics, the aim of this study was to investigate the AgNPs effect on first trimester human trophoblasts. The HTR8/SVneo cell line was treated with AgNPs (0.3-1.5 pM), for 6 and 24 h. Cell viability, reactive nitrogen and oxygen species (RNS and ROS) production, nitric oxide synthase expression, antioxidant defenses and biomolecule damage were evaluated. The exposure to AgNPs produced changes in HTR8/SVneo cell morphology and decreased cell viability. Alterations in redox balance were observed, with an increase in ROS and RNS levels, and NOS2 protein expression. Superoxide dismutase and catalase augmented their activity accompanied with a decreased in glutathione content and glutathione S-transferase activity. Protein oxidation and genotoxic damage were observed at concentrations greater than 0.6 pM. The pre-incubation with l-NMMA, NAC, mannitol and peroxidase demonstrated that AgNPs-induced cytotoxicity was not mediated by HO and H₂O₂, but nitric oxide and glutathione pathways were implicated in cell death. Since reported AgNPs microbicidal mechanism is mediated by increasing ROS (mainly HO and H₂O₂) without an increase in RNS, this work indicates an interesting difference in the reactive species and oxidative pathways involved in AgNPs toxicity in eukaryotic and prokaryotic cells. Highlighting the importance of toxicity evaluation to determine the safety of AgNPs with pharmaceutical potential uses.

Biocompatible exosomes nanodrug cargo for cancer cell bioimaging and drug delivery

Therapy against cancer remains a daunting issue for human health, despite remarkable innovations in many areas of pathology. In situ biosynthesized nanoclusters bestow a novel remedy for carcinogenic cell imaging. Exosomes have received special attention as an efficient tool for the diagnosis of various diseases, including cancers. All types of cells (healthy or diseased) generate exosomes, making them significantly unique for relevant disease diagnosis and treatment. In this contribution, we exploit the possibility of utilizing the exosomes to facilitate chemotherapeutics, viz. the combination of doxorubicin (Dox) and biosynthesized silver nanoclusters in cancer cells. Our study showed a new facile way for bioimaging of cancer cells using biosynthesized silver-DNA nanoclusters, and thus further targeting cancer cells using the relevant cancer exosomes as drug delivery cargo. After isolating exosomes from neoplastic cells, i.e. HeLa, loaded with the drug, and treating other neoplastic cells with cargo-loaded isolated exosomes, we found that cargo-loaded isolated exosomes can readily enter into the targeted cancer cells and efficiently kill these neoplastic cells. This raises the possibility of acting as a novel facile modality for target cancer theranostics with high efficiency and biocompability.

Successful in-vivo treatment of mice infected with Candida glabrata using silver nanoparticles

The current study describes the production of silver nanoparticles (AgNPs) to treat Candida glabrata infections. The method involved incubation of silver nitrate (AgNO3) with Aspergillus terreus using a green and straightforward route. The production of AgNPs was confirmed through a color change from transparent yellow to brown as well as by ultraviolet-visible (UV-VIS) spectroscopy. The surface morphology of AgNPs was assessed using a scanning electron microscope. The antifungal activity of AgNPs against C. glabrata was investigated in the serum of 20 infected mice. The mice were divided into four groups, and the level of cytokines: IL-4 and IFN-γ were examined after 21 days. The atomic force microscopy confirmed that the average diameter of AgNPs was 25.1 nm, which is appropriate for delivering silver nanoparticles to treat animals' infection. The concentration of cytokines IL-4 and IFN-γ were significantly (P < 0.05) higher in the C. glabrata-infected group than in the control group. While the cytokines level remained close to average concentration in mice administrated with AgNPs, such a result was comparable with the fourth group of mice (Candida-treated Aspergillus) after treatment with AgNPs.

Biogenic synthesis of silver nanoparticles using Gliocladium deliquescens and their application as household sponge disinfectant

The topic of this investigation was to evaluate the microbial contamination of household sponges, biosynthesize of silver nanoparticles (Ag NPs) by Gliocladium deliquescens cell-free supernatant, and estimate the efficiency of Ag NPs as an acceptable disinfectant. The 2³ factorial design was applied for the optimization of Ag NPs synthesis. Silver nitrate (AgNO₃) concentration was the main positive impact on Ag NP biosynthesis. Various gamma irradiation doses were used in Ag NP production where the highest yield production was at 25.0 kGy. Ag NPs were characterized by UV-Vis. spectroscopy, The Fourier-transform infrared spectroscopy analysis (FTIR), dynamic light scattering (DLS), X-ray diffraction (XRD), and transmission electron microscope (TEM). Ag NPs were monodispersed spherical-shaped with 9.68 nm mean size. Two hundred sponge samples that were collected from different Egyptian household furniture and kitchens were highly contaminated by various contaminants including Salmonella spp., Staphylococcus spp., coliform bacteria, Gram-negative bacteria, yeasts, and molds. Ag NPs showed functional antimicrobial activity against all the microbial contaminants; Salmonella spp. was completely inhibited by Ag NP (50.0 μg/mL) treatment. The Ag NPs have the maximum inhibition zone against Salmonella spp. (14 mm) compared with the Staphylococcus spp. (12.3 mm). The minimum inhibitory concentration (MIC) of Ag NPs against Salmonella spp. and Staphylococcus spp. were 6.25 μg/ mL and 12.5 μg/ mL, respectively. The antibiofilm activity of Ag NPs was the highest at the concentration of 50.0 μg/mL recording 63.3 % for Salmonella spp. and 54.5 % for Staphylococcus spp. Ag NPs may find potent disinfectant applications for household purposes.

Bacteriostatic effects of nanometer silver disinfectant on the biofilms in dental unit water lines

Background/purpose

Dental unit water lines (DUWLs) may be contaminated by aerobic bacteria in clinical settings and comprehensive disinfecting methods should be considered without delay. Herein, this study aims to investigate the timeliness and dynamic bacteriostatic effects of different forms of nanometer silver (NMS) disinfectant on bio-film in DUWLs.

Materials and methods

Bacterial DUWLs samples were respectively treated with different NMS forms, including liquid phase and solid phase at the concentrations of 0.25%, 0.5%, 1% and 2% and their bacteriostatic effects were observed at the 1st, 4th, 7th, 14th, ^28th day.

Results

The bacteriostatic effects of liquid phase NMS at all concentrations were unsatisfactory and the bacteriostatic rate was only 20% at the 1st day. However, there appeared massive bacteria growth at the 4th, 7th, 14th, 28th day. Comparatively, no bacteria growth was found at the 1st, 4th, 7th, 14th, ^28th day after sterilizing with different concentrations of solid phase NMS and the bacteriostatic rate was 100%.

Conclusion

Microbial contamination in DUWLs can be disinfected by different NMS forms, among which solid phase NMS is more bactericidal against bacteria bio-films, demonstrating significant roles of solid phase NMS in preventing DUWL contamination.

Production, characterization and antibacterial activity of silver nanoparticles produced by Fusarium oxysporum and monitoring of protein-ligand interaction through in-silico approaches

The present study envisages biological production of silver nanoparticles using Fusarium oxysporum and in-silico identification of the antibacterial activity of the nanoparticles using protein-ligand interaction studies. The morphology of the nanoparticles was variable, with majority of them spherical in the size range 1-50 nm. For in-silico studies, two microorganisms, Escherichia coli and Pseudomonas aeruginosa were selected and metal docking was carried out using the licensed software SYBYL X 1.1.1. The ligand docked deeply into the binding pockets of the outer membrane proteins (OMPs) of both E. coli and P. aeruginosa. The results showed that silver may prove to be a strong antibacterial agent against both the pathogens, with the antibacterial action of silver being greater in the case of P. aeruginosa. The results obtained through in-silico studies were further validated by in-vitro approaches on both solid and liquid media to confirm the results obtained by in-silico analysis. The corroboration of in-silico and in-vitro results amply demonstrates the immense antibacterial potential of silver nanoparticles against the selected pathogens.

Silver nanoparticles induce Egr-1-dependent psoriasin expression via the ERK and p38 pathways

BACKGROUND

Silver nanoparticles (Ag-NPs) can prevent bacterial infection and improve cutaneous wound healing owing to their antimicrobial activity. However, the mechanism of their antimicrobial activity is poorly understood.

AIM

To determine the mechanistic relationship between Ag-NP treatment and expression of psoriasin.

METHODS

Human epidermal keratinocytes, neonatal (HEKn) were used. Psoriasin mRNA expression was measured by reverse transcription PCR and real-time PCR. Western blotting was performed to verify expression of early growth response-1 (Egr-1) and psoriasin, and phosphorylation of mitogen-activated protein kinase (MAPK). Psoriasin promoter activity by Egr-1 was detected by a luciferase assay.

RESULTS

Treatment of HEKn with Ag-NPs induced psoriasin mRNA and protein expression. Upregulation of psoriasin promoter activity was also observed in the luciferase assay. Ag-NPs increased Egr-1 expression, promoter activity and nuclear translocation in HEKn. Psoriasin luciferase activity was increased in HEKn transfected with Egr-1 pcDNA 3.1. Ag-NPs activated MAPK pathways including the extracellular signal-regulated kinase (ERK), p38, and c-Jun-N-terminal kinase (JNK) pathways. The upregulation of Egr-1 expression by Ag-NP stimulation was inhibited by ERK and p38 inhibitors, but not by a JNK inhibitor. Psoriasin expression was reduced in Egr-1 small interfering RNA-transfected HEKn.

CONCLUSIONS

Ag-NP treatment induces upregulation of psoriasin expression through Egr-1 expression. We suggest that the ERK and p38 pathways are involved in Egr-1-dependent psoriasin expression.

Comparison of Antimicrobial Properties of Silver Nanoparticles Synthesized from Selected Bacteria

Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions and the microbial source. The antimicrobial activity of AgNPs biosynthesized by Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Acinetobacter baumannii (confirmed clinical isolate) were investigated in this study. Biosynthesis conditions (AgNO3 concentration, pH, incubation temperature and incubation time) were optimized to obtain the maximum AgNP yield. Presence of AgNPs was confirmed by observing a characteristic UV-Visible absorbance peak in 420-435 nm range. AgNP biosynthesis was optimal at 0.4 g/L AgNO3 concentration under alkaline conditions at 60-70 °C. The biosynthesized AgNPs showed higher stability compared to chemogenized AgNPs in the presence of electrolytes. AgNPs synthesized by P. aeruginosa were the most stable while NPs of S. aureus were the least stable. AgNPs synthesized by P. aeruginosa and S. aureus showed good antimicrobial potential against E. coli, P. aeruginosa, S. aureus, MRSA and Candida albicans. AgNPs synthesized by S. aureus had greater antimicrobial activity. The antimicrobial activity of NPs may vary depending on the size and the morphology of NPs.

Biofabrication of silver nanoparticles using bacteria from mangrove swamp

The last decade has observed a rapid advancement in utilising biological system towards bioremediation of metal ions in the form of respective metal nanostructures or microstructures. The process may also be adopted for respective metal nanoparticle biofabrication. Among different biological methods, bacteria-mediated method is gaining great attention for nanoparticle fabrication due to their eco-friendly and cost-effective process. In the present study, silver nanoparticle (AgNP) was synthesised via continuous biofabrication using Aeromonas veronii, isolated from swamp wetland of Sunderban, West Bengal, India. The biofabricated AgNP was further purified to remove non-conjugated biomolecules using size exclusion chromatography, and the purified AgNPs were characterised using UV-visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy (TEM). Additionally, the presence of proteins as capping and stabilising agents was confirmed by the amide-I and amide-II peaks in the spectra obtained using attenuated total reflection Fourier transform infrared spectroscopy. The size of biofabricated AgNP was 10-20 nm, as observed using TEM. Additionally, biofabricated AgNP shows significant antibacterial potential against E. coli and S. aureus. Hence, biofabricated AgNP using Aeromonas veronii, which found resistant to a significant concentration of Ag ion, showed enhanced antimicrobial activity compared to commercially available AgNP.

Emphasized Mechanistic Antimicrobial Study of Biofunctionalized Silver Nanoparticles on Model Proteus mirabilis

Antimicrobial study of biofunctionalized silver nanoparticles has been done with the emphasis on its mechanism on both gram positive and negative bacteria. The biofunctionalized silver nanoparticles are employed considering their importance in green chemistry with respect to easy synthesis, usefulness, and economic synthetic procedure involved. The stability of these nanoparticles was determined by zeta potential analyzer. The probable mechanism of antibacterial activity was performed on Proteus mirabilis by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDAX) study which does not show the presence of silver. The free radicals generated by silver nanoparticles were responsible for lethal antibacterial activity by rupturing the cell surface which causes improper nutrient and signal supply. Free radical scavenging efficacy of silver nanoparticles was confirmed by 1,1-Diphenyl-2-picrylhydrazyl (DPPH) method. AgNP enhanced the membrane leakage of reducing sugars by destroying the proteins existing on the cell wall. These nanoparticles are found to be toxic against human pathogens and are highly effective on Staphylococcus aureus. The effect of silver nanoparticles is concentration dependent and independent of the type of strains used.

Antibacterial, Antiproliferative, and Immunomodulatory Activity of Silver Nanoparticles Synthesized with Fucans from the Alga Dictyota mertensii

In this study, we aimed to synthesize silver nanoparticles containing fucans from Dictyota mertensii (Martius) Kützing using an environmentally friendly method and to characterize their structure as well as antiproliferative, immunomodulatory, and antibacterial effects. Fucan-coated silver nanoparticles (FN) were characterized by Fourier-transform infrared analysis, dynamic light scattering, zeta potential, atomic force microscopy, energy dispersive X-ray spectroscopy, and inductively coupled plasma emission spectrometry. They were evaluated for their effect on cell viability, minimum inhibitory bactericidal concentration, and release of nitric oxide and cytokines. The FN were successfully synthesized using an environmentally friendly method. They were size-stable for 16 months, of a spherical shape, negative charge (-19.1 mV), and an average size of 103.3 ± 43 nm. They were able to inhibit the proliferation of the melanoma tumor cell line B16F10 (60%). In addition, they had immunomodulatory properties: they caused an up to 7000-fold increase in the release of nitric oxide and cytokines (IL-10; IL-6 and TNF-α) up to 7000 times. In addition, the FN showed inhibitory effect on Gram-positive and -negative bacteria, with MIC values of 50 µg/mL. Overall, the data showed that FN are nanoparticles with the potential to be used as antitumor, immunomodulatory, and antibacterial agents.