Two-Phase Bactericidal Mechanism of Silver Nanoparticles against Burkholderia pseudomallei

Precision-engineered metal and metal-oxide nanoparticles for biomedical imaging and healthcare applications

The growing field of nanotechnology has witnessed numerous advancements over the past few years, particularly in the development of engineered nanoparticles. Compared with bulk materials, metal nanoparticles possess more favorable properties, such as increased chemical activity and toxicity, owing to their smaller size and larger surface area. Metal nanoparticles exhibit exceptional stability, specificity, sensitivity, and effectiveness, making them highly useful in the biomedical field. Metal nanoparticles are in high demand in biomedical nanotechnology, including Au, Ag, Pt, Cu, Zn, Co, Gd, Eu, and Er. These particles exhibit excellent physicochemical properties, including amenable functionalization, non-corrosiveness, and varying optical and electronic properties based on their size and shape. Metal nanoparticles can be modified with different targeting agents such as antibodies, liposomes, transferrin, folic acid, and carbohydrates. Thus, metal nanoparticles hold great promise for various biomedical applications such as photoacoustic imaging, magnetic resonance imaging, computed tomography (CT), photothermal, and photodynamic therapy (PDT). Despite their potential, safety considerations, and regulatory hurdles must be addressed for safe clinical applications. This review highlights advancements in metal nanoparticle surface engineering and explores their integration with emerging technologies such as bioimaging, cancer therapeutics and nanomedicine. By offering valuable insights, this comprehensive review offers a deep understanding of the potential of metal nanoparticles in biomedical research.

A Comprehensive Review of Silver and Gold Nanoparticles as Effective Antibacterial Agents

The increasing threat from antibiotic-resistant bacteria has necessitated the development of novel methods to counter bacterial infections. In this context, the application of metallic nanoparticles (NPs), especially gold (Au) and silver (Ag), has emerged as a promising strategy due to their remarkable antibacterial properties. This review examines research published between 2006 and 2023, focusing on leading journals in nanotechnology, materials science, and biomedical research. The primary applications explored are the efficacy of Ag and Au NPs as antibacterial agents, their synthesis methods, morphological properties, and mechanisms of action. An extensive review of the literature on NPs synthesis, morphology, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and effectiveness against various Gram(+/-) bacteria confirms the antibacterial efficacy of Au and Ag NPs. The synthesis methods and characteristics of NPs, such as size, shape, and surface charge, are crucial in determining their antibacterial activity, as these factors influence their interactions with bacterial cells. Furthermore, this review underscores the urgent necessity of standardizing synthesis techniques, MICs, and reporting protocols to enhance the comparability and reproducibility of future studies. Standardization is essential for ensuring the reliability of research findings and accelerating the clinical application of NP-based antimicrobial approaches. This review aims to propel NP-based antimicrobial strategies by elucidating the properties that enhance the antibacterial activity of Ag and Au NPs. By highlighting their inhibitory effects against various bacterial strains and relatively low cytotoxicity, this work positions Ag and Au NPs as promising materials for developing antibacterial agents, making a significant contribution to global efforts to combat antibiotic-resistant pathogens.

Resistance mechanisms of Saccharomyces cerevisiae against silver nanoparticles with different sizes and coatings

To investigate the underlying resistance mechanisms of Saccharomyces cerevisiae against Ag-NPs with different particle sizes and coatings, transcriptome sequencing (RNA-seq) technology was used to characterize the transcriptomes from S. cerevisiae exposed to 20-PVP-Ag, 100-PVP-Ag, 20-CIT-Ag and 100-CIT-Ag, respectively. The steroid biosynthesis was found as a general pathway for Ag-NPs stress responding, in which ERG6 and ERG3 were inhibited and ERG11, ERG25 and ERG5 were significantly up-regulated to resist the stress by supporting the later mutation and resistance and modulate drug efflux indirectly. The resistance mechanism of S. cerevisiae to 20-PVP-Ag seems different from that of 100-PVP-Ag, 20-CIT-Ag and 100-CIT-Ag. Under the 20-PVP-Ag, transmembrane transporter activity, transition metal ion homeostasis and oxidative phosphorylation pathway were main resistance pathways to enhance cell transport processes. While 100-PVP-Ag, 20-CIT-Ag and 100-CIT-Ag mainly impacted RNA binding, structural constituent of ribosome and ribosome pathway which can provide more energy to maintain the number and function of protein in cells. This study reveals the differences in resistance mechanisms of S. cerevisiae to Ag-NPs with different particle sizes and coatings, and explains several main regulatory mechanisms used to respond to silver stress. It will provide theoretical basis for the study of chemical risk assessment.

Antimicrobial, Antibiofilm, and Anticancer Activities of Syzygium aromaticum Essential Oil Nanoemulsion

In the current study, clove oil nanoemulsion (CL-nanoemulsion) and emulsion (CL-emulsion) were prepared through an ecofriendly method. The prepared CL-nanoemulsion and CL-emulsion were characterized using dynamic light scattering (DLS) and a transmission electron microscope (TEM), where results illustrated that CL-nanoemulsion droplets were approximately 32.67 nm in size and spherical in shape, while CL-nanoemulsion droplets were approximately 225.8 nm with a spherical shape. The antibacterial activity of CL-nanoemulsion and CL-emulsion was carried out using a microbroth dilution method. Results revealed that the preferred CL-nanoemulsion had minimal MIC values between 0.31 and 5 mg/mL. The antibiofilm efficacy of CL-nanoemulsion against S. aureus significantly decreased the development of biofilm compared with CL-emulsion. Furthermore, results illustrated that CL-nanoemulsion showed antifungal activity significantly higher than CL-emulsion. Moreover, the prepared CL-nanoemulsion exhibited outstanding antifungal efficiency toward Candida albicans, Cryptococcus neoformans, Aspergillus brasiliensis, A. flavus, and A. fumigatus where MICs were 12.5, 3.12, 0.78, 1.56, and 1.56 mg/mL, respectively. Additionally, the prepared CL-nanoemulsion was analyzed for its antineoplastic effects through a modified MTT assay for evaluating apoptotic and cytotoxic effects using HepG2 and MCF-7 cell lines. MCF-7 breast cancer cells showed the lowest IC50 values (3.4-fold) in CL-nanoemulsion relative to that of CL-emulsion. Thus, CL-nanoemulsion induces apoptosis in breast cancer cells by inducing caspase-8 and -9 activity and suppressing VEGFR-2. In conclusion, the prepared CL-nanoemulsion had antibacterial, antifungal, and antibiofilm as well as anticancer properties, which can be used in different biomedical applications after extensive studies in vivo.

Efflux systems as a target for anti-biofilm nanoparticles: perspectives on emerging applications

INTRODUCTION

Understanding the role of efflux pumps in biofilm resistance provides valuable insights for developing effective therapeutic strategies. Drugs designed for targeting efflux pumps in drug design holds promise for combating biofilm-related infections. Nanoparticles offer unparalleled advantages in designing drugs targeting efflux pumps.

AREAS COVERED

This review rigorously examines the existing body of knowledge on the prospective targeting of efflux pumps using metal-based nanoparticles. It includes and analyses the pertinent research findings sourced from the PubMed and SciFinder databases. It covers the experimental studies on efflux inhibition by nanoparticles and provides detailed analyses of their mechanisms of action, elucidating their interactions with the efflux system and their influence on biofilm formation and persistence.

EXPERT OPINION

The potential of nanoparticles to act as potent antibacterial agents through efflux pump inhibition remains tantalizing, although hindered by limited mechanistic understanding. From the burgeoning research landscape nanoparticles emerge as a novel direction for shaping antimicrobial drug design. Notably, beyond their contribution to drug resistance, efflux pumps play a pivotal role in biofilm development. The deliberate disruption of these pumps can effectively reduce biofilm adhesion and maturation. More details however are needed to exploit this potential.

Analysis of Capped Silver Nanoparticles Combined with Imipenem against Different Susceptibility Profiles of Klebsiella pneumoniae

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic bacterium that has drawn attention due to its resistance to carbapenem antibiotics. The treatment of patients with severe infections has been challenging. Thus, silver nanoparticles (AgNPs) have been applied for their antimicrobial effects. This work aims to analyze the synergistic effect of the carbapenem antibiotic Imipenem with AgNPs against different susceptibility clinical profiles of K. pneumoniae. The silver nanoparticles were synthesized by bottom-up methodology and capped with alpha-lipoic acid. Susceptibility tests were performed using four K. pneumoniae strains with different susceptibility profiles to Imipenem. The strains were induced to form a biofilm for 48 h. Crystal violet and Resazurin assays were performed to determine biofilm formation and minimal inhibitory concentration, respectively. The reduction in Imipenem concentration with the association of nanoparticles was found in all strains studied in planktonic form, and the synergism between silver nanoparticles and Imipenem was demonstrated through the analysis of the fractional inhibitory concentration index. The viability percentage was reduced at rates ≥80% in the biofilm analysis, characterized by the minimal biofilm inhibitory concentration. The study’s proposed association resulted in inhibitory effects on different K. pneumoniae profiles, both in planktonic forms and biofilm, with peculiar behavior in the Imipenem-resistant profile.

TA-AgNPs/Alginate Hydrogel and Its Potential Application as a Promising Antibiofilm Material against Polymicrobial Wound Biofilms Using a Unique Biofilm Flow Model

The presence of biofilm within a chronic wound may delay the healing process. Thus, control of biofilm formation and providing bactericidal effect are crucial factors for wound healing management. Alginate-based nanocomposite hydrogels have been suggested as dressing materials for wound treatment, which are employed as a biocompatible matrix. Therefore, in this study, we aimed to develop a biocompatible antimicrobial wound dressing containing AgNPs and demonstrate its efficacy against polymicrobial wound biofilms by using a biofilm flow device to simulate a chronic infected, exuding wound and specific wound environment. The results from agar well diffusion, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays showed that TA-AgNPs exhibited antibacterial activity against wound pathogens. Additionally, the Minimum Biofilm Eradication Concentration assay (MBEC) demonstrated it could impair biofilm formation. Importantly, our TA-AgNPs/Alginate hydrogel clearly showed antibacterial activities against Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa. Furthermore, we used the biofilm flow device to test the topical antimicrobial hydrogel against a three-species biofilm. We found that TA-AgNPs/Alginate hydrogel significantly showed a 3-4 log reduction in bacterial numbers when applied with multiple doses at 24 h intervals, and was especially effective against the chronic wound pathogen P. aeruginosa. This work highlighted that the TA-AgNPs/Alginate hydrogel is a promising material for treating complex wound biofilms.

Leveraging the potential of silver nanoparticles-based materials towards sustainable water treatment

Increasing demand of pure and accessible water and improper disposal of waste into the existing water resources are the major challenges for sustainable development. Nanoscale technology is an effective approach that is increasingly being applied to water remediation. Compared to conventional water treatment processes, silver nanotechnology has been demonstrated to have advantages due to its anti-microbial and oligodynamic (biocidal) properties. This review is focused on environmentally friendly green syntheses of silver nanoparticles (AgNPs) and their applications for the disinfection and microbial control of wastewater. A bibliometric keyword analysis is conducted to unveil important keywords and topics in the utilisation of AgNPs for water treatment applications. The effectiveness of AgNPs, as both free nanoparticles (NPs) or as supported NPs (nanocomposites), to deal with noxious pollutants like complex dyes, heavy metals as well as emerging pollutants of concern is also discussed. This knowledge dataset will be helpful for researchers to identify and utilise the distinctive features of AgNPs and will hopefully stimulate the development of novel solutions to improve wastewater treatment. This review will also help researchers to prepare effective water management strategies using nano silver-based systems manufactured using green chemistry.

Synthesis of Silver Nanocomposite Based on Carboxymethyl Cellulose: Antibacterial, Antifungal and Anticancer Activities

Traditional cancer treatments include surgery, radiation, and chemotherapy. According to medical sources, chemotherapy is still the primary method for curing or treating cancer today and has been a major contributor to the recent decline in cancer mortality. Nanocomposites based on polymers and metal nanoparticles have recently received the attention of researchers. In the current study, a nanocomposite was fabricated based on carboxymethyl cellulose and silver nanoparticles (CMC-AgNPs) and their antibacterial, antifungal, and anticancer activities were evaluated. The antibacterial results revealed that CMC-AgNPs have promising antibacterial activity against Gram-negative (Klebsiella oxytoca and Escherichia coli) and Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus). Moreover, CMC-AgNPs exhibited antifungal activity against filamentous fungi such as Aspergillus fumigatus, A. niger, and A. terreus. Concerning the HepG2 hepatocellular cancer cell line, the lowest IC₅₀ values (7.9 ± 0.41 µg/mL) were recorded for CMC-AgNPs, suggesting a strong cytotoxic effect on liver cancer cells. As a result, our findings suggest that the antitumor effect of these CMC-Ag nanoparticles is due to the induction of apoptosis and necrosis in hepatic cancer cells via increased caspase-8 and -9 activities and diminished levels of VEGFR-2. In conclusion, CMC-AgNPs exhibited antibacterial, antifungal, and anticancer activities, which can be used in the pharmaceutical and medical fields.

Design, Characterization, and Antibacterial Performance of MAPLE-Deposited Coatings of Magnesium Phosphate-Containing Silver Nanoparticles in Biocompatible Concentrations

Bone disorders and traumas represent a common type of healthcare emergency affecting men and women worldwide. Since most of these diseases imply surgery, frequently complicated by exogenous or endogenous infections, there is an acute need for improving their therapeutic approaches, particularly in clinical conditions requiring orthopedic implants. Various biomaterials have been investigated in the last decades for their potential to increase bone regeneration and prevent orthopedic infections. The present study aimed to develop a series of MAPLE-deposited coatings composed of magnesium phosphate (Mg₃(PO₄)₂) and silver nanoparticles (AgNPs) designed to ensure osteoblast proliferation and anti-infective properties simultaneously. Mg₃(PO₄)₂ and AgNPs were obtained through the cooling bath reaction and chemical reduction, respectively, and then characterized through X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Selected Area Electron Diffraction (SAED). Subsequently, the obtained coatings were evaluated by Infrared Microscopy (IRM), Fourier-Transform Infrared Spectroscopy (FT-IR), and Scanning Electron Microscopy (SEM). Their biological properties show that the proposed composite coatings exhibit well-balanced biocompatibility and antibacterial activity, promoting osteoblasts viability and proliferation and inhibiting the adherence and growth of Staphylococcus aureus and Pseudomonas aeruginosa, two of the most important agents of orthopedic implant-associated infections.

Andrographolide stabilized-silver nanoparticles overcome ceftazidime-resistant Burkholderia pseudomallei: study of antimicrobial activity and mode of action

Burkholderia pseudomallei (B. pseudomallei) is a Gram-negative pathogen that causes melioidosis, a deadly but neglected tropical disease. B. pseudomallei is intrinsically resistant to a growing list of antibiotics, and alternative antimicrobial agents are being sought with urgency. In this study, we synthesize andrographolide-stabilized silver nanoparticles (andro-AgNPs, spherically shaped with 16 nm average diameter) that show excellent antimicrobial activity against B. pseudomallei, including ceftazidime-resistant strains, being 1-3 orders of magnitude more effective than ceftazidime and 1-2 orders of magnitude more effective than other green-synthesized AgNPs. The andro-AgNPs are meanwhile non-toxic to mammalian cell lines. The mode of action of Andro-AgNPs toward B. pseudomallei is unraveled by killing kinetics, membrane neutralization, silver ions (Ag+) release, reactive oxygen species (ROS) induction, membrane integrity, and cell morphology change studies. The antimicrobial activity and mode of action of andro-AgNPs against B. pseudomallei reported here may pave the way to alternative treatments for melioidosis.

Bell Shape Curves of Hemolysis Induced by Silver Nanoparticles: Review and Experimental Assay

The hemolytic activity assay is a versatile tool for fast primary toxicity studies. This work presents a systematic study of the hemolytic properties of ArgovitTM silver nanoparticles (AgNPs) extensively studied for biomedical applications. The results revealed an unusual and unexpected bell-shaped hemolysis curve for human healthy and diabetic donor erythrocytes. With the decrease of pH from 7.4 and 6.8 to 5.6, the hemolysis profiles for AgNPs and AgNO3 changed dramatically. For AgNPs, the bell shape changed to a step shape with a subsequent sharp increase, and for AgNO3 it changed to a gradual increase. Explanations of these changes based on the aggregation of AgNPs due to the increase of proton concentration were suggested. Hemolysis of diabetic donor erythrocytes was slightly higher than that of healthy donor erythrocytes. The meta-analysis revealed that for only one AgNPs formulation (out of 48), a bell-shaped hemolysis profile was reported, but not discussed. This scarcity of data was explained by the dominant goal of studies consisting in achieving clinically significant hemolysis of 5-10%. Considering that hemolysis profiles may be bell-shaped, it is recommended to avoid extrapolations and to perform measurements in a wide concentration interval in hemolysis assays.

Broad Spectrum Anti-Bacterial Activity and Non-Selective Toxicity of Gum Arabic Silver Nanoparticles

Silver nanoparticles (AgNPs) are the most commercialized nanomaterials and presumed to be biocompatible based on the biological effects of the bulk material. However, their physico-chemical properties differ significantly to the bulk materials and are associated with unique biological properties. The study investigated the antimicrobial and cytotoxicity effects of AgNPs synthesized using gum arabic (GA), sodium borohydride (NaBH4), and their combination as reducing agents. The AgNPs were characterized using ultraviolet-visible spectrophotometry (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The anti-bacterial activity was assessed using agar well diffusion and microdilution assays, and the cytotoxicity effects on Caco-2, HT-29 and KMST-6 cells using MTT assay. The GA-synthesized AgNPs (GA-AgNPs) demonstrated higher bactericidal activity against all bacteria, and non-selective cytotoxicity towards normal and cancer cells. AgNPs reduced by NaBH4 (C-AgNPs) and the combination of GA and NaBH4 (GAC-AgNPs) had insignificant anti-bacterial activity and cytotoxicity at ≥50 µg/mL. The study showed that despite the notion that AgNPs are safe and biocompatible, their toxicity cannot be overruled and that their toxicity can be channeled by using biocompatible polymers, thereby providing a therapeutic window at concentrations that are least harmful to mammalian cells but toxic to bacteria.

A Biological Study of Anisotropic Silver Nanoparticles and Their Antimicrobial Application for Topical Use

The excessive use of antibiotics in both human and veterinary medicine has contributed to the development and rapid spread of drug resistance in bacteria. Silver nanoparticles (AgNPs) have become a tool of choice that can be used to treat these resistant bacteria. Several studies have shown that AgNPs have antibacterial and wound healing properties. In this study, we evaluated the biological activity of anisotropic AgNPs to develop an antimicrobial gel formulation for treating wound infections. We showed that some anisotropic AgNPs (S2) have an effective antibacterial activity against bacterial pathogens and low cytotoxicity to keratinocytes and fibroblasts in vitro. The MIC and MBC values were in the range of 2-32 µg/mL, and cytotoxicity had IC₅₀ values of 68.20 ± 9.71 µg/mL and 68.65 ± 10.97 µg/mL against human keratinocyte and normal human dermal fibroblast cells, respectively. The anisotropic AgNPs (S2) were used as a gel component and tested for antibacterial activity, including long-term protection, compared with povidone iodine, a common antiseptic agent. The results show that the anisotropic AgNPs can inhibit the growth of most tested bacterial pathogens and provide protection longer than 48 h, whereas povidone iodine only inhibits the growth of some bacteria. This study suggests that anisotropic AgNPs could be used as an alternative antimicrobial agent for treating bacterial skin infection and as a wound healing formulation.

Green Synthesis and Characterization of Carboxymethyl Cellulose Fabricated Silver-Based Nanocomposite for Various Therapeutic Applications

Purpose

The current study proposed the simple, eco-friendly and cost-effective synthesis of carboxymethyl cellulose (CMC) structured silver-based nanocomposite (CMC-AgNPs) using Syzygium aromaticum buds extract.

Methods

The CMC-AgNPs were characterized by ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transmission infra-red (FTIR), energy-dispersive X-ray (EDX), and dynamic light scattering (DLS) techniques. The synthesized nanocomposites were evaluated for their bactericidal kinetics, in-vivo anti-inflammatory, anti-leishmaniasis, antioxidant and cytotoxic activities using different in-vitro and in-vivo models.

Results

The spherical shape nanocomposite of CMC-AgNPs was synthesized with the mean size range of 20–30 nm, and the average pore diameter is 18.2 nm while the mean zeta potential of −31.6 ± 3.64 mV. The highly significant (P < 0.005) antibacterial activity was found against six bacterial strains with the ZIs of 24.6 to 27.9 mm. More drop counts were observed in Gram-negative strains after 10 min exposure with CMC-AgNPs. Significant damage in bacterial cell membrane was also observed in atomic force microscopy (AFM) after treated with CMC-AgNPs. Nanocomposite showed highly significant anti-inflammatory activity in cotton pellet induced granuloma model (Phase I) in rats with the mean inhibitions of 43.13% and 48.68% at the doses of 0.025 and 0.05 mg/kg, respectively, when compared to control. Reduction in rat paw edema (Phase II) was also highly significant (0.025 mg/kg; 42.39%; 0.05 mg/kg, 47.82%). At dose of 0.05 mg/kg, CMC-AgNPs caused highly significant decrease in leukocyte counts (922 ± 83), levels of CRP (8.4 ± 0.73 mg/mL), IL-1 (177.4 ± 21.3 pg/mL), IL-2 (83.7 ± 11.5 pg/mL), IL-6 (83.7 ± 11.5 pg/mL) and TNF-α (18.3 ± 5.3 pg/mL) as compared to control group. CMC-AgNPs produced highly effective anti-leishmaniasis activity with the viable Leishmania major counts decreased up to 36.7% within 24 h, and the IC₅₀ was found to be 28.41 μg/mL. The potent DPPH radical scavenging potential was also observed for CMC-AgNPs with the IC₅₀ value of 112 μg/mL. Furthermore, the cytotoxicity was assessed using HeLa cell lines with the LC₅₀ of 108.2 μg/mL.

Conclusion

The current findings demonstrate positive attributes of CMC fabricated AgNPs as a promising antibacterial, anti-inflammatory, anti-leishmaniasis, and antioxidant agent with low cytotoxic potential.

Silver Nanoparticles Enhance Antimicrobial Efficacy of Antibiotics and Restore That Efficacy against the Melioidosis Pathogen

Melioidosis is an infectious disease caused by Gram-negative bacillus bacteria Burkholderia pseudomallei. Due to the emerging resistance of B. pseudomallei to antibiotics including ceftazidime (CAZ), the development of novel antibiotics and alternative modes of treatment has become an urgent issue. Here, we demonstrated an ability to synergistically increase the efficiency of antibiotics through their combination with silver nanoparticles (AgNPs). Combinations of four conventional antibiotics including CAZ, imipenem (IMI), meropenem (MER), and gentamicin sulfate (GENT) with starch-stabilized AgNPs were tested for their antibacterial effects against three isolates of B. pseudomallei. The combination of each antibiotic with AgNPs featured fractional inhibitory concentration (FIC) index values and fractional bactericidal concentration (FBC) index values ranging from 0.312 to 0.75 µg/mL and 0.252 to 0.625 µg/mL, respectively, against the three isolates of B. pseudomallei. The study clearly showed that most of the combinatorial treatments exhibited synergistic antimicrobial effects against all three isolates of B. pseudomallei. The highest enhancing effect was observed for GENT with AgNPs. These results confirmed the combination of each antibiotic with AgNPs restored their bactericidal potency in the bacterial strains that had previously been shown to be resistant to the antibiotics. In addition, morphological changes examined by SEM confirmed that the bacterial cells were severely damaged by combinations at the FBC level. Although bacteria produce fibers to protect themselves, ultimately the bacteria were killed by the antibiotic-AgNPs combinations. Overall, these results suggest the study of antibiotic-AgNPs combinations as an alternative design strategy for potential therapeutics to more effectively combat the melioidosis pathogen.

Prevention of nosocomial transmission and biofilm formation on novel biocompatible antimicrobial gloves impregnated with biosynthesized silver nanoparticles synthesized using Eucalyptus citriodora leaf extract

Failure in the prevention of cross-transmission from contaminated gloves has been recognized as an important factor that contributes to the spread of several healthcare-associated infections. Ex situ coating process with silver nanoparticles (AgNPs) using Eucalyptus citriodora ethanolic leaf extract as reducing and capping agents to coat glove surfaces has been developed to prevent this mode of transmission. Elemental analysis of coated gloves showed 24.8 Wt% silver densely adhere on the surface. The coated gloves fully eradicated important hospital-acquired pathogens including Gram-positive bacteria, Gram-negative bacteria, and yeasts within 1 h. The coated gloves showed significant reduction, an average of five logs when tested against all standard strains and most clinical isolates (p < 0.01). Following prolonged exposure, the coating significantly reduced the numbers of most adhered pathogenic species, compared with uncoated gloves (p < 0.0001). AgNPs-coated gloves reduced microbial adhesion of mixed-species biofilms. A series of contamination and transmission assays demonstrated no transmission of viable organisms. Biocompatibility analysis confirmed high viability of HaCaT and L929 cells at all concentrations of AgNPs tested. The coated gloves were non-toxic with direct contact with L929 cells. The highly efficacious AgNPs-coated gloves potentially provide additional protection against transmission of healthcare-associated infections.

Hemolysis of Human Erythrocytes by Argovit™ AgNPs from Healthy and Diabetic Donors: An In Vitro Study

The use of nanomaterials is becoming increasingly widespread, leading to substantial research focused on nanomedicine. Nevertheless, the lack of complete toxicity profiles limits nanomaterials' uses, despite their remarkable diagnostic and therapeutic results on in vitro and in vivo models. Silver nanoparticles (AgNPs), particularly Argovit™, have shown microbicidal, virucidal, and antitumoral effects. Among the first-line toxicity tests is the hemolysis assay. Here, the hemolytic effect of Argovit™ AgNPs on erythrocytes from one healthy donor (HDE) and one diabetic donor (DDE) is evaluated by the hemolysis assay against AgNO3. The results showed that Argovit™, in concentrations ≤24 µg/mL of metallic silver, did not show a hemolytic effect on the HDE or DDE. On the contrary, AgNO3 at the same concentration of silver ions produces more than 10% hemolysis in both the erythrocyte types. In all the experimental conditions assessed, the DDE was shown to be more prone to hemolysis than the HDE elicited by Ag+ ions or AgNPs, but much more evident with Ag+ ions. The results show that Argovit™ is the least hemolytic compared with the other twenty-two AgNP formulations previously reported, probably due to the polymer mass used to stabilize the Argovit™ formulation. The results obtained provide relevant information that contributes to obtaining a comprehensive toxicological profile to design safe and effective AgNP formulations.

Green Synthesized Silver Nanoparticles: Antibacterial and Anticancer Activities, Biocompatibility, and Analyses of Surface-Attached Proteins

The increasing number of multi-drug-resistant bacteria and cancer cases, that are a real threat to humankind, forces research world to develop new weapons to deal with it. Biogenic silver nanoparticles (AgNPs) are considered as a solution to this problem. Biosynthesis of AgNPs is regarded as a green, eco-friendly, low-priced process that provides small and biocompatible nanostructures with antimicrobial and anticancer activities and potential application in medicine. The biocompatibility of these nanoparticles is related to the coating with biomolecules of natural origin. The synthesis of AgNPs from actinobacterial strain was confirmed using UV-Vis spectroscopy while their morphology, crystalline structure, stability, and coating were characterized using, transmission electron microscopy (TEM), X-ray diffraction (XRD), Zeta potential and Fourier transform infrared spectroscopy (FTIR). Antibacterial activity of biogenic AgNPs was evaluated by determination of minimum inhibitory and minimum biocidal concentrations (MIC and MBC) against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The potential mechanism of antibacterial action of AgNPs was determined by measurement of ATP level. Since the use of AgNPs in biomedical applications depend on their safety, the in vitro cytotoxicity of biosynthesized AgNPs on MCF-7 human breast cancer cell line and murine macrophage cell line RAW 264.7 using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, cell lactate dehydrogenase (LDH) release and measurement of reactive oxygen species (ROS) level were assessed. The nanoparticle protein capping agent that can be involved in reduction of silver ions to AgNPs and their stabilization was identified using LC-MS/MS. Nanoparticles were spherical in shape, small in size (mean 13.2 nm), showed crystalline nature, good stability (-18.7 mV) and presence of capping agents. They exhibited antibacterial activity (MIC of 8-128 μg ml^-1, MBC of 64-256 μg ml^-1) and significantly decreased ATP levels in bacterial cells after treatment with different concentrations of AgNPs. The in vitro analysis showed that the AgNPs demonstrated dose-dependent cytotoxicity against RAW 264.7 macrophages and MCF-7 breast cancer cells but higher against the latter than the former. Cell viability decrease was found to be 42.2-14.2 and 38.0-15.5% while LDH leakage 14.6-42.7% and 19.0-45.0%, respectively. IC₅₀ values calculated for MTT assay was found to be 16.3 and 12.0 μg ml^-1 and for LDH assay 102.3 and 76.2 μg ml^-1, respectively. Moreover, MCF-7 cells released a greater amount of ROS than RAW 264.7 macrophages during stimulation with all tested concentrations of AgNPs (1.47-3.13 and 1.02-2.58 fold increase, respectively). The SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) analysis revealed the presence of five protein bands at a molecular weight between 31.7 and 280.9 kDa. These proteins showed the highest homology to hypothetical proteins and porins from E. coli, Delftia sp. and Pseudomonas rhodesiae. Based on obtained results it can be concluded that biogenic AgNPs were capped with proteins and demonstrated potential as antimicrobial and anticancer agent.

Green Synthesized Silver Nanoparticles: Antibacterial and Anticancer Activities, Biocompatibility, and Analyses of Surface-Attached Proteins

The increasing number of multi-drug-resistant bacteria and cancer cases, that are a real threat to humankind, forces research world to develop new weapons to deal with it. Biogenic silver nanoparticles (AgNPs) are considered as a solution to this problem. Biosynthesis of AgNPs is regarded as a green, eco-friendly, low-priced process that provides small and biocompatible nanostructures with antimicrobial and anticancer activities and potential application in medicine. The biocompatibility of these nanoparticles is related to the coating with biomolecules of natural origin. The synthesis of AgNPs from actinobacterial strain was confirmed using UV-Vis spectroscopy while their morphology, crystalline structure, stability, and coating were characterized using, transmission electron microscopy (TEM), X-ray diffraction (XRD), Zeta potential and Fourier transform infrared spectroscopy (FTIR). Antibacterial activity of biogenic AgNPs was evaluated by determination of minimum inhibitory and minimum biocidal concentrations (MIC and MBC) against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The potential mechanism of antibacterial action of AgNPs was determined by measurement of ATP level. Since the use of AgNPs in biomedical applications depend on their safety, the in vitro cytotoxicity of biosynthesized AgNPs on MCF-7 human breast cancer cell line and murine macrophage cell line RAW 264.7 using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, cell lactate dehydrogenase (LDH) release and measurement of reactive oxygen species (ROS) level were assessed. The nanoparticle protein capping agent that can be involved in reduction of silver ions to AgNPs and their stabilization was identified using LC-MS/MS. Nanoparticles were spherical in shape, small in size (mean 13.2 nm), showed crystalline nature, good stability (-18.7 mV) and presence of capping agents. They exhibited antibacterial activity (MIC of 8-128 μg ml-1, MBC of 64-256 μg ml-1) and significantly decreased ATP levels in bacterial cells after treatment with different concentrations of AgNPs. The in vitro analysis showed that the AgNPs demonstrated dose-dependent cytotoxicity against RAW 264.7 macrophages and MCF-7 breast cancer cells but higher against the latter than the former. Cell viability decrease was found to be 42.2-14.2 and 38.0-15.5% while LDH leakage 14.6-42.7% and 19.0-45.0%, respectively. IC50 values calculated for MTT assay was found to be 16.3 and 12.0 μg ml-1 and for LDH assay 102.3 and 76.2 μg ml-1, respectively. Moreover, MCF-7 cells released a greater amount of ROS than RAW 264.7 macrophages during stimulation with all tested concentrations of AgNPs (1.47-3.13 and 1.02-2.58 fold increase, respectively). The SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) analysis revealed the presence of five protein bands at a molecular weight between 31.7 and 280.9 kDa. These proteins showed the highest homology to hypothetical proteins and porins from E. coli, Delftia sp. and Pseudomonas rhodesiae. Based on obtained results it can be concluded that biogenic AgNPs were capped with proteins and demonstrated potential as antimicrobial and anticancer agent.

Colorimetric detection of Hg(II) by γ-aminobutyric acid-silver nanoparticles in water and the assessment of antibacterial activities

In this work, we report the synthesis of silver nanoparticles (AgNPs) via a wet-chemical reduction procedure using citrate (Cit) and γ-aminobutyric acid (GABA) as stabilizers. The formation of GABA-Cit@AgNPs was confirmed by UV-vis spectroscopy with a surface plasmon resonance band at 393 nm clearly confirming the formation of silver nanoparticles. AgNPs were characterized using UV-vis spectroscopy, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential. The as-prepared AgNPs can be used for the detection of hazardous mercury ions (Hg²⁺) in water by colorimetric method with a limit of detection (LOD) and limit of quantitation (LOQ) of 2.37 μM and 3.99 μM, respectively. The linear working range for Hg²⁺ detection is 5-35 μM and the sensor probe was applied to investigate Hg²⁺ in real drinking water samples with satisfied results. Rapid response to Hg²⁺ is also observed when the nanoparticles are composited within hydrogels. Moreover, GABA-Cit@AgNPs shows antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The fast and sensitive response of the proposed Hg²⁺ sensor, together with its antibacterial activities, makes GABA-Cit@AgNPs potentially applicable for the development of cheap, portable, colorimetric sensors in fieldwork.

Antimicrobial nanomedicine for ocular bacterial and fungal infection

Ocular infection induced by bacteria and fungi is a major cause of visual impairment and blindness. Topical administration of antibiotics remains the first-line treatment, as effective eradication of pathogens is the core of the anti-infection strategy. Whereas, eye drops lack efficiency and have relatively low bioavailability. Intraocular injection may cause concurrent ocular damage and secondary infection. In addition, antibiotic-based management can be limited by the low sensitivity to multidrug-resistant bacteria. Nanomedicine is proposed as a prospective, effective, and noninvasive platform to mediate ocular delivery and combat pathogen or even resistant strains. Nanomedicine can not only carry antimicrobial agents to fight against pathogens but also directly active microbicidal capability, killing pathogens. More importantly, by modification, nanomedicine can achieve enhanced residence time and release time on the cornea, and easy penetration through corneal tissues into anterior and posterior segments of the eye, thus improving the therapeutic effect for ocular infection. In this review, several categories of antimicrobial nanomedicine are systematically discussed, where the efficiency and possibility of further embellishment and improvement to adapt to clinical use are also investigated. All in all, novel antimicrobial nanomedicine provides potent and prospective ways to manage severe and refractory ocular infections.

In vitro and in vivo assessments of inspired Ag/80S bioactive nanocomposites against carbapenem-resistant Klebsiella pneumoniae

In 2017 the World Health Organization listed carbapenem-resistant K. pneumoniae as a critical priority for developing a novel antimicrobial agent. Here we report on our investigation of the antibacterial efficacy of silver nanoparticles (AgNPs), confined to a mesostructured material and designated as an Ag/80S bioactive nanocomposite, against carbapenem-resistant K. pneumoniae. Results from a textural analysis indicate a 7.5 nm mesopore size and 307.6 m²/g surface area for Ag/80S. UV-Vis spectrum and transmission electron microscope images of Ag/80S revealed a uniform AgNP size distribution with an approximately 3.5 nm average. ICP-MS analysis demonstrated a significantly higher silver content in TSB (a protein-rich environment) compared to ultrapure water, suggesting a controllable release of Ag/80S and thus designated as the inspired Ag/80S. Minimum inhibitory concentration (MIC) values against 16 K. pneumoniae isolates ranged from 0.25 to 0.5% (2.5 to 5.0 mg/ml). NIH 3T3 fibroblast viability at 0.25% exceeded 80% and at 0.5% just under 70%, suggesting low cytotoxicity. Mechanistic study results indicate that the inspired Ag/80S attached to and deformed bacterial cells and induced a time-dependent accumulation of reactive oxygen species, leading to bacterial death. Further, inspired Ag/80S significantly extended median survival time in a Caenorhabditis elegans animal model infected with carbapenem-resistant K. pneumoniae ATCC BAA-1705. Combined, we found a novel Ag/80S which could prevent aggregation of AgNP and control its release via a specific environment for medical use against carbapenem-resistant K. pneumoniae.

Plant-mediated synthesis of nanoparticles and their antimicrobial activity against phytopathogens

Nanotechnology is an emerging science with a wide array of applications involving the synthesis and manipulation of materials with dimensions in the range of 1-100 nm. Nanotechnological applications include diverse fields such as pharmaceuticals, medicine, the environment, food processing and agriculture. Regarding the latter, applications are mainly focused on plant growth and crop protection against plagues and diseases. In recent years, the biogenic reduction of elements such as Ag, Au, Cu, Cd, Al, Se, Zn, Ce, Ti and Fe with plant extracts has become one of the most accepted techniques for obtaining nanoparticles (NPs), as it is considered an ecological and cost-effective process without the use of chemical contaminants. The objective of this work was to review NPs synthesized by green chemistry using vegetable extracts, as well as their use as antimicrobial agents against phytopathogenic fungi and bacteria. Given the need for alternatives to control and integrate management of phytopathogens, this review is relevant to agriculture, although this technology is barely exploited in this field. © 2020 Society of Chemical Industry.

Tannic Acid-Stabilized Silver Nanoparticles Used in Biomedical Application as an Effective Antimelioidosis and Prolonged Efflux Pump Inhibitor against Melioidosis Causative Pathogen

Burkholderia pseudomallei is the causative pathogen of melioidosis and this bacterium is resistant to several antibiotics. Silver nanoparticles (AgNPs) are an interesting agent to develop to solve this bacterial resistance. Here, we characterize and assess the antimelioidosis activity of AgNPs against these pathogenic bacteria. AgNPs were characterized and displayed a maximum absorption band at 420 nm with a spherical shape, being well-monodispersed and having high stability in solution. The average size of AgNPs is 7.99 ± 1.46 nm. The antibacterial efficacy of AgNPs was evaluated by broth microdilution. The bactericidal effect of AgNPs was further assessed by time-kill kinetics assay. Moreover, the effect of AgNPs on the inhibition of the established biofilm was investigated by the crystal violet method. In parallel, a study of the resistance induction development of B. pseudomallei towards AgNPs with efflux pump inhibiting effect was performed. We first found that AgNPs had strong antibacterial activity against both susceptible and ceftazidime-resistant (CAZ-resistant) strains, as well as being efficiently active against B. pseudomallei CAZ-resistant strains with a fast-killing mode via a bactericidal effect within 30 min. These AgNPs did not only kill planktonic bacteria in broth conditions, but also in established biofilm. Our findings first documented that the resistance development was not induced in B. pseudomallei toward AgNPs in the 30th passage. We found that AgNPs still showed an effective efflux pump inhibiting effect against these bacteria after prolonged exposure to AgNPs at sublethal concentrations. Thus, AgNPs have valuable properties for being a potent antimicrobial agent to solve the antibiotic resistance problem in pathogens.

The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

Zinc oxide nanoparticles (ZnO NPs) are applied in various applications in catalysis, biosensing, imaging, and as antibacterial agents. Here we to prepare ZnO nanomaterials decorated by γ-amino butyric acid (GABA), curcumin derivatives (CurBF₂) and silver nanoparticles (CurBF₂-AgNPs). The structures of all ZnO nanostructures were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-VIS spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Further, their antibacterial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were investigated through analysis of minimum inhibitory concentration (MIC) method. Among the prepared nanostructures, the ZnO NPs-GABA/CurBF₂-AgNPs showed excellent antibacterial activity against both Gram-positive and -negative bacteria. ZnO NPs fabricated here may have potential use in future anti-bacterial compositions and coatings technologies.

Nano-Modified Titanium Implant Materials: A Way Toward Improved Antibacterial Properties

Titanium and its alloys have superb biocompatibility, low elastic modulus, and favorable corrosion resistance. These exceptional properties lead to its wide use as a medical implant material. Titanium itself does not have antibacterial properties, so bacteria can gather and adhere to its surface resulting in infection issues. The infection is among the main reasons for implant failure in orthopedic surgeries. Nano-modification, as one of the good options, has the potential to induce different degrees of antibacterial effect on the surface of implant materials. At the same time, the nano-modification procedure and the produced nanostructures should not adversely affect the osteogenic activity, and it should simultaneously lead to favorable antibacterial properties on the surface of the implant. This article scrutinizes and deals with the surface nano-modification of titanium implant materials from three aspects: nanostructures formation procedures, nanomaterials loading, and nano-morphology. In this regard, the research progress on the antibacterial properties of various surface nano-modification of titanium implant materials and the related procedures are introduced, and the new trends will be discussed in order to improve the related materials and methods.

AgNP/Alginate Nanocomposite hydrogel for antimicrobial and antibiofilm applications

The synthesis and specific surface functionalization of antimicrobial silver nanoparticles (AgNPs) and their incorporation into an alginate hydrogel is described. Divalent cation-mediated ionic crosslinking was used to disperse the AgNPs throughout the gel, made possible by -COO^- cross-linking sites provided by the surface-enhanced nanoparticles, inspired by the classic egg-box model crosslinking of calcium alginate. An AgNP concentration, 10-20 μg g^-1 increased hygrogel elasticity, viscosity, and shear resistance by 45, 30, and 31% respectively. Cryo-TEM revealed evenly distributed AgNP assemblies of discrete AgNPs throughout the gel matrices. FTIR-ATR indicated AgNPs were involved in alginate carboxylate-Ca²⁺-COO^-AgNP crossbridging, which was not achieved through mixing of AgNPs into preformed gels. Live/dead fluorometric assays determined a minimal bactericidal concentration of 25 μg g^-1 Ag for 6 microorganisms. Anti-biofilm assays showed species-dependent cell death of 44 -61%, with limited silver ion release of 0.41% and 1.1% after 7 days for Gram positive and negative bacteria, respectively.

Silver, copper, and copper hydroxy salt decorated fumed silica hybrid composites as antibacterial agents

Decoration of matrices such as silicates, graphene, etc. is an efficient technique in order to develop multifunctional materials with enhanced properties, which are of use for microbial control. Consequently, it leads to an increased search for alternative matrices and synthesis methods for decoration. Herein, decoration of a fumed silica is proposed, with structures that consisted of silver (Ag@FS), copper hydroxy salt (CuHS@FS), and copper (Cu@FS), for antibacterial applications. With the simple combination of the metal precursor salt, the appropriate solvent, and the fumed silica, the composites were obtained by one-pot solvothermal (200 °C for 1 h), rapid (2 min) microwave assisted precipitation, and by ascorbic acid chemical reduction, respectively. Characterization by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM) proved the successful decoration of the fumed silica with layered copper hydroxy salt (90 width x 970 length nm) and round-like metallic Ag (210 nm) and Cu (370 nm) particles. Fourier transformed infrared (FTIR) and Raman spectroscopy evidenced the presence of SiOMetal interactions. The antibacterial activity was evaluated against the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, giving inhibition and bactericidal values between 3-12 mg/ mL and 12-24 mg/ mL, respectively, with a maximum ion liberation ratio of 1.4 %. The application of the fumed silica presented here, is an attractive alternative to existing matrices, in order to fabricate multifunctional materials, as it is ready-to-use and feasible for large-scale production. Moreover, the applied synthesis routes provide rapid approaches for decoration, creating composites useful for antibacterial applications.

Microcellular Environmental Regulation of Silver Nanoparticles in Cancer Therapy: A Critical Review

Silver nanoparticles (AgNPs) play significant roles in various cancer cells such as functional heterogeneity, microenvironmental differences, and reversible changes in cell properties (e.g., chemotherapy). There is a lack of targets for processes involved in tumor cellular heterogeneity, such as metabolic clampdown, cytotoxicity, and genotoxicity, which hinders microenvironmental biology. Proteogenomics and chemical metabolomics are important tools that can be used to study proteins/genes and metabolites in cells, respectively. Chemical metabolomics have many advantages over genomics, transcriptomics, and proteomics in anticancer therapy. However, recent studies with AgNPs have revealed considerable genomic and proteomic changes, particularly in genes involved in tumor suppression, apoptosis, and oxidative stress. Metabolites interact biochemically with energy storage, neurotransmitters, and antioxidant defense systems. Mechanobiological studies of AgNPs in cancer metabolomics suggest that AgNPs may be promising tools that can be exploited to develop more robust and effective adaptive anticancer therapies. Herein, we present a proof-of-concept review for AgNPs-based proteogenomics and chemical metabolomics from various tumor cells with the help of several technologies, suggesting their promising use as drug carriers for cancer therapy.

Emerging role of biologics for the treatment of melioidosis and glanders

Introduction: Two important pathogenic species within the genus Burkholderia, namely Burkholderia pseudomallei (Bpm) and Burkholderia mallei (Bm), are the causative agents of the life-threatening diseases melioidosis and glanders, respectively. Due to their high mortality rate and potential for aerosolization, they have gained interest as potential biothreat agents and are classified as Tier 1 Select Agents.Areas covered: The manuscript provides an overview of the literature covering the efforts taken in the last 10 years to develop new therapeutics measures against both Bpm and Bm, with attention on novel therapeutic agents.Expert Opinion: As a result of the complicated antibiotic regimens necessary to treat these infections, development of novel therapeutics is needed to treat both diseases. In recent years, the understanding of the pathogenesis of Burkholderia has improved significantly and so have the efforts to develop novel therapeutic agents with high efficacy, either alone, or in combination with conventional antibiotics.

Controlled Synthesis of Triangular Silver Nanoplates by Gelatin–Chitosan Mixture and the Influence of Their Shape on Antibacterial Activity

Triangular silver nanoplates were prepared by using the seeding growth approach with the presence of citrate-stabilized silver seeds and a mixture of gelatin–chitosan as the protecting agent. By understanding the critical role of reaction components, the synthesis process was improved to prepare the triangular nanoplates with high yield and efficiency. Different morphologies of silver nanostructures, such as triangular nanoplates, hexagonal nanoprisms, or nanodisks, can be obtained by changing experimental parameters, including precursor AgNO3 volume, gelatin–chitosan concentration ratios, and the pH conditions. The edge lengths of triangular silver nanoplates were successfully controlled, primarily through the addition of silver nitrate under appropriate condition. As-prepared triangular silver nanoplates were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-Vis, Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Silver nanoplates had an average edge length of 65–80 nm depending on experimental conditions and exhibited a surface plasma resonance absorbance peak at 340, 450, and 700 nm. The specific interactions of gelatin and chitosan with triangular AgNPs were demonstrated by FT-IR. Based on the characterization, the growth mechanism of triangular silver nanoplates was theoretically proposed regarding the twinned crystal of the initial nanoparticle seeds and the crystal face-blocking role of the gelatin–chitosan mixture. Moreover, the antibacterial activity of triangular silver nanoplates was considerably improved in comparison with that of spherical shape when tested against Gram-positive and Gram-negative bacteria species, with 6.0 ug/mL of triangular silver nanoplates as the MBC (Minimum bactericidal concentration) for Escherichia coli and Vibrio cholera, and 8.0 ug/mL as the MBC for Staphylococcus aureus and Pseudomonas aeruginosa. The MIC (Minimum inhibitory concentration) of triangular Ag nanoplates was 4.0 ug/mL for E. coli, V. cholera, S. aureus, and P. aeruginosa.

Impact of adding metal nanoparticles on anaerobic digestion performance - A review

Anaerobic digestion is the most widely adopted biological waste treatment processes with renewable energy production. The effects of adding metal nanoparticles (NPs) on improving digestion performance are well noted. This paper reviewed the traditional view on the cytotoxicity of NPs to living organisms and the contemporary view of mechanisms for enhancement in anaerobic digestion performance in the presence of metal NPs. The complicated interactions acquire further studies for comprehending the physical and chemical interactions of metal NPs to the constituent compounds and to the living cells, and the involvement of mechanisms such as direct interspecies electron transfer for better design and control of the "NP strategy" for anaerobic digestion performance enhancement.

Eucalyptus citriodora leaf extract-mediated biosynthesis of silver nanoparticles: broad antimicrobial spectrum and mechanisms of action against hospital-acquired pathogens

Pathogen resistance to conventional antibiotics has become a serious clinical and public health problem, making the development of an alternative mean a very urgent issue. Recently, biosynthesis of silver nanoparticles (AgNPs) was successfully accomplished in the presence of Eucalyptus citriodora leaf extract as a reducing agent. In this study, the antimicrobial mechanisms of AgNPs against important hospital-acquired pathogens, including Gram-positive, Gram-negative bacteria, and fungi were further assessed. The results indicated that AgNPs could enhance a broad antimicrobial spectrum against drug-resistant organisms, with a range of minimum inhibitory concentration from 0.02 to 0.36 μg/mL. Time-kill assay showed that AgNPs produced bactericidal effects on the microorganisms. AgNPs could significantly reduce biofilm production in pathogens without affecting growth of the pathogens (p < 0.05). AgNPs inhibited cell viability and biofilm formation in a dose-dependent manner. Cell membrane damage in microorganisms resulting from effects of AgNPs was observed. A significant increase in per cent uptake of crystal violet was observed in all isolates treated with AgNPs when compared with the control (p < 0.05). Upon treatment with AgNPs, the surface charge of the reference strains and clinical isolates of pathogens moved towards neutral. The alteration of surface potential after exposure to AgNPs could contribute to membrane disruption and cell viability. Scanning electron microscopy further confirmed morphological cell changes and disrupted the cell membrane. Increasing resistance to AgNPs was not induced by stepwise isolation of the bacteria after 45 passages on Luria-Bertani agar supplemented with AgNPs. Furthermore, AgNPs was not toxic to red blood cells.

Biosynthesis of Silver Nanoparticles Mediated by Extracellular Pigment from Talaromyces purpurogenus and Their Biomedical Applications

In recent years, green syntheses have been researched comprehensively to develop inexpensive and eco-friendly approaches for the generation of nanoparticles. In this context, plant and microbial sources are being examined to discover potential reducing agents. This study aims to utilize an extracellular pigment produced by Talaromyces purpurogenus as a prospective reducing agent to synthesize silver nanoparticles (AgNPs). Biosynthesized AgNPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), electron probe micro analyser (EPMA), and zeta potential. The pigment functional groups involved in the generation of AgNPs were investigated using Fourier transform infrared spectroscopy. TEM images showed that the generated nanoparticles were spherical, hexagonal, rod-shaped, and triangular-shaped with a particle size distribution from 4 to 41 nm and exhibited a surface plasmon resonance at around 410 nm. DLS and zeta potential studies revealed that the particles were polydispersed and stable (−24.8 mV). EPMA confirmed the presence of elemental silver in the samples. Biosynthesized AgNPs exhibited minimum inhibitory concentrations of 32 and 4 μg/mL against E. coli and S. epidermidis, respectively. Further, cytotoxicity of the AgNPs was investigated against human cervical cancer (HeLa), human liver cancer (HepG2), and human embryonic kidney (HEK-293) cell lines using 5-fluorouracil as a positive control. A significant activity was recorded against HepG2 cell line with a half-maximal inhibitory concentration of 11.1 μg/mL.

Potential antibacterial mechanism of silver nanoparticles and the optimization of orthopedic implants by advanced modification technologies

Infection, as a common postoperative complication of orthopedic surgery, is the main reason leading to implant failure. Silver nanoparticles (AgNPs) are considered as a promising antibacterial agent and always used to modify orthopedic implants to prevent infection. To optimize the implants in a reasonable manner, it is critical for us to know the specific antibacterial mechanism, which is still unclear. In this review, we analyzed the potential antibacterial mechanisms of AgNPs, and the influences of AgNPs on osteogenic-related cells, including cellular adhesion, proliferation, and differentiation, were also discussed. In addition, methods to enhance biocompatibility of AgNPs as well as advanced implants modifications technologies were also summarized.

Antibacterial effects of microbial synthesized silver-copper nanoalloys on Escherichia coli, Burkholderia cepacia, Listeria monocytogenes and Brucella abortus

BACKGROUND AND OBJECTIVES

Bacterial resistance is an emerging public health problem worldwide. Metallic nanoparticles and nanoalloys open a promising field due to their excellent antimicrobial effects. The aim of the present study was to investigate the antibacterial effects of Ag-Cu nanoalloys, which were biosynthesized by Lactobacillus casei ATCC 39392, on some of the important bacterial pathogens, including Escherichia coli, Burkholderia cepacia, Listeria monocytogenes and Brucella abortus.

MATERIALS AND METHODS

Ag-Cu nanoalloys were synthesized through the microbial reduction of AgNO3 and CuSO4 by Lactobacillus casei ATCC39392. Furthermore, they were characterized by Fourier-Transform Infrared Spectrometer (FTIR) and Field Emission Scanning Electron Microscopy (FESEM) analysis in order to investigate their chemical composition and morphological features, respectively. The minimum inhibitory and minimum bactericidal concentrations of Ag-Cu nanoalloys were determined against each strain. The bactericidal test was conducted on the surface of MHA supplemented with 1, 0.1, and 0.01 μg/μL of the synthesized nanoalloy. The antimicrobial effects of synthesized nanoalloy were compared with ciprofloxacin, ampicillin and ceftazidime as positive controls.

RESULTS

Presence of different chemical functional groups, including N-H, C-H, C-N and C-O on the surface of Ag-Cu nanoalloys was recorded by FTIR. FESEM micrographs revealed uniformly distributed nanoparticles with spherical shape and size ranging from 50 to 100 nm. The synthesized Ag-Cu nanoalloys showed antibacterial activity against L. monocytogenes PTCC 1298, E. coli ATCC 25922 and B. abortus vaccine strain. However, no antibacterial effects were observed against B. cepacia ATCC 25416.

CONCLUSION

According to the findings of the present research, the microbially synthesized Ag-Cu nanoalloy demonstrated antibacterial effects on the majority of the bacteria studied even at 0.01 μg/μL. However, complementary investigations should be conducted into the safety of this nanoalloy for in vivo or systemic use.

Redox-active nanomaterials for nanomedicine applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.