Antibacterial activity and mechanism of silver nanoparticles against multidrug-resistant Pseudomonas aeruginosa

Critical Antileishmanial in vitro Effects of Highly Examined Gold Nanoparticles

Introduction

The current therapeutic armory for visceral leishmaniasis (VL) caused by Leishmania donovani complex is inadequate, coupled with serious limitations. Combination therapy has proved ineffective due to mounting resistance; however, the search for safe and effective drugs is desirable, in the absence of any vaccine. There is a growing interest in the application of nanoparticles for the therapeutic effectiveness of leishmaniasis. Aimed in this direction, we assessed the antileishmanial effect of gold nanoparticles (GNP) against L. donovani in vitro.

Methods

GNP were synthesized and characterized for particle size by dynamic light scattering (DLS) and atomic force microscopy (AFM) and for optical properties by UV-visible spectroscopy. Cytotoxicity of GNP was measured by the MTT proliferation assay. The antileishmanial activity of the nanoparticles was evaluated against L. donovani promastigotes and macrophage-infected amastigotes in vitro.

Results

GNP showed a strong SPR peak at 520 nm and mean particle size, polydispersity index (PDI), and zeta potential of 56.0 ± 10 nm, 0.3 ± 0.1 and −27.0 ± 3 mV, respectively. The GNPs were smooth and spherical with a mean particle diameter of 20 ± 5 nm. Nanoparticles [1.2–100 µM] did not reveal any cytotoxicity on RAW 264.7 murine macrophage cell line, but exerted significant activity against both promastigotes and amastigote stages of L. donovani with 50% inhibitory concentrations (IC₅₀) of 18.4 ± 0.4 µM and 5.0 ± 0.3 µM, respectively. GNP showed significant antileishmanial activity with deformed morphology of parasites and the least number of surviving promastigotes after growth reversibility analysis.

Conclusion

GNP may provide a platform to conjugate antileishmanial drugs onto the surface of nanoparticles to enhance their therapeutic effectiveness against VL. Further work is warranted, involving more in-depth mechanistic studies and in vivo investigations.

Printable Resin Modified by Grafted Silver Nanoparticles for Preparation of Antifouling Microstructures with Antibacterial Effect

The usage of three-dimensional (3D) printed materials in many bioapplications has been one of the fastest-growing sectors in the nanobiomaterial industry in the last couple of years. In this work, we present a chemical approach for grafting silver nanoparticles (AgNPs) into a resin matrix, which is convenient for 3D printing. In this way, the samples can be prepared and are able to release silver ions (Ag⁺) with excellent antibacterial effect against bacterial strains of E. coli and S. epidermidis. By the proposed process, the AgNPs are perfectly mixed and involved in the polymerization process and their distribution in the matrix is homogenous. It was also demonstrated that this approach does not affect the printing resolution and the resin is therefore suitable for the construction of microstructures enabling controlled silver ion release and antifouling properties. At the same time the physical properties of the material, such as viscosity and elasticity modulus are preserved. The described approach can be used for the fabrication of facile, low-cost 3D printed resin with antifouling-antibacterial properties with the possibility to control the release of Ag⁺ through microstructuring.

Antimicrobial effect of Casiopeinas® copper- and ruthenium-based compounds on Aggregatibacter actinomycetemcomitans and in vitro cell viability onto osteoblasts cells

OBJECTIVES

The present study aims to evaluate the antimicrobial property of Casiopeinas® copper- and ruthenium-based compounds against Aggregatibacter actinomycetemcomitans serotype b (ATCC® 43,718™), as well as the cytotoxicity on an osteoblasts cell line of both compounds.

MATERIAL AND METHODS

The antibacterial effect of the copper-based compounds (CasII-gly, CasIII-ia) and the ruthenium-based compound (RuN-6) at four different concentrations was evaluated as the inhibition ratio of the bacterial growth after 48 h under anaerobic conditions, and the cell viability was measured through resazurin assay.

RESULTS

The copper- and ruthenium-based compounds used for this assay were (CasII-gly, CasIII-ia, and RuN-6), showing inhibitory activity between 39 and 62% compared to the antibiotic employed as control 66%. Cell viability was established between 61 and 96%.

CONCLUSIONS

Casiopeinas® and ruthenium showed dose and time dependent, inhibitory activity on A. actinomycetemcomitans, and low toxicity on cells (osteoblast) underexposure. The compound CasII-gly showed the best antimicrobial effect, and it could be considered a possible antimicrobial agent in periodontal therapy.

Green synthesis of silver nanoparticles using Hagenia abyssinica (Bruce) J.F. Gmel plant leaf extract and their antibacterial and anti-oxidant activities

Green synthesis of silver nanoparticles (AgNPs) was achieved by bio-reduction of silver nitrate using Hagenia Abyssinica plant leaf extract (HAPLE). The AgNPs formation was confirmed by Ultraviolet-Visible (UV-Vis) spectrophotometer. The synthesized AgNPs in solution have shown maximum absorption at 430 nm. The different parameters like temperature, pH, time, silver nitrate concentration and volume of leaf extract were optimized spectrophotometrically. The Fourier-Transform Infrared (FTIR) Spectroscopy was used to confirm the existence of various functional groups responsible for reducing and stabilizing during the biosynthesis process. The X-Ray Diffraction (XRD) analysis confirmed the structure, crystal size and nature of the AgNPs. The synthesized AgNPs showed antimicrobial (gram-negative bacteria (klebsiella pneumoniae and salmonella typhimurium) and gram-positive bacteria (Streptococcus pneumoniae)) and antioxidant (2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging method) activities. The developed method for the AgNPs synthesis using HAPLE is an eco-friendly and convenient method. In near future, the synthesized AgNPs could be used in the fields of water treatment, biomedicine, biosensor and nanotechnology.

Insight into the Antibacterial Activity of Selected Metal Nanoparticles and Alterations within the Antioxidant Defence System in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis

The antimicrobial activity of nanoparticles (NPs) is a desirable feature of various products but can become problematic when NPs are released into different ecosystems, potentially endangering living microorganisms. Although there is an abundance of advanced studies on the toxicity and biological activity of NPs on microorganisms, the information regarding their detailed interactions with microbial cells and the induction of oxidative stress remains incomplete. Therefore, this work aimed to develop accurate oxidation stress profiles of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis strains treated with commercial Ag-NPs, Cu-NPs, ZnO-NPs and TiO2-NPs. The methodology used included the following determinations: toxicological parameters, reactive oxygen species (ROS), antioxidant enzymes and dehydrogenases, reduced glutathione, oxidatively modified proteins and lipid peroxidation. The toxicological studies revealed that E. coli was most sensitive to NPs than B. cereus and S. epidermidis. Moreover, NPs induced the generation of specific ROS in bacterial cells, causing an increase in their concentration, which further resulted in alterations in the activity of the antioxidant defence system and protein oxidation. Significant changes in dehydrogenases activity and elevated lipid peroxidation indicated a negative effect of NPs on bacterial outer layers and respiratory activity. In general, NPs were characterised by very specific nano-bio effects, depending on their physicochemical properties and the species of microorganism.

Synthesis and Antibacterial Activity of Silver Nanoparticles Against Escherichia coli and Pseudomonas sp

Silver nanoparticles (AgNPs) have been synthesized by chemical reduction method using ascorbic acid as reducing agent. Silver nitrate (AgNO[Formula: see text] and sodium dodecyl sulfate (SDS) have been used as precursor and stabilizer, respectively. The prepared samples were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The antibacterial activity of prepared silver nanoparticles has been assessed by using the disc diffusion method against pathogenic, gram-negative bacterial strains including Escherichia coli and Pseudomonassp. To evaluate the potential antibacterial properties of AgNPs, the discs have been impregnated and dried with three different doses like 50, 100 and 150[Formula: see text][Formula: see text]l of 20[Formula: see text][Formula: see text]g/ml concentrated AgNPs solution and placed on the Petri-dishes. The antibiotic kanamycin (5[Formula: see text][Formula: see text]g) was used as control. In all the cases, a clear and distinct zone of inhibition is observed, which suggests that AgNPs can be used as effective growth inhibitors of various bacterial species and would be promising candidate for future development of antibacterial agents.

Study of Antibacterial and Anticancer Properties of bioAgNPs Synthesized Using Streptomyces sp. PBD-311B and the Application of bioAgNP-CNC/Alg as an Antibacterial Hydrogel Film against P. aeruginosa USM-AR2 and MRSA

Here, we report the extracellular biosynthesis of silver nanoparticles (AgNPs) and determination of their antibacterial and anticancer properties. We also explore the efficacy of bioAgNPs incorporated in cellulose nanocrystals (CNCs) and alginate (Alg) for the formation of an antibacterial hydrogel film. Streptomyces sp. PBD-311B was used for the biosynthesis of AgNPs. The synthesized bioAgNPs were characterized using UV-Vis spectroscopy, TEM, XRD, and FTIR analysis. Then, the bioAgNPs’ antibacterial and anticancer properties were determined using TEMA and cytotoxicity analysis. To form the antibacterial hydrogel film, bioAgNPs were mixed with a CNC and Alg solution and further characterized using FTIR analysis and a disc diffusion test. The average size of the synthesized bioAgNPs is around 69 ± 2 nm with a spherical shape. XRD analysis confirmed the formation of silver nanocrystals. FTIR analysis showed the presence of protein capping at the bioAgNP surface and could be attributed to the extracellular protein binding to bioAgNPs. The MIC value of bioAgNPs against P. aeruginosa USM-AR2 and MRSA was 6.25 mg/mL and 3.13 mg/mL, respectively. In addition, the bioAgNPs displayed cytotoxicity effects against cancer cells (DBTRG-0.5MG and MCF-7) and showed minimal effects against normal cells (SVG-p12 and MCF-10A), conferring selective toxicity. Interestingly, the bioAgNPs still exhibited inhibition activity when incorporated into CNC/Alg, which implies that the hydrogel film has antibacterial properties. It was also found that bioAgNP-CNC/Alg displayed a minimal or slow release of bioAgNPs owing to the intermolecular interaction and the hydrogel’s properties. Overall, bioAgNP-CNC/Alg is a promising antibacterial hydrogel film that showed inhibition against the pathogenic bacteria P. aeruginosa and MRSA and its application can be further evaluated for the inhibition of cancer cells. It showed benefits for surgical resection of a tumor to avoid post-operative wound infection and tumor recurrence at the surgical site.

Exploration of the Wound Healing Potential of Thermoplastic Polyurethane Electrospun Membrane Incorporated with Phenolic Acids in Spenceria ramalana Trimen

Wound healing process is usually accompanied by infection and the wound dressing loaded with antibiotics is usually used to treat skin wound. However, the intensive use of antibiotics may lead to development of resistance and the antibiotic resistance has become a major global problem. Finding new wound dressing with sustained antibacterial property to overcome the problem of resistance is one of clinical challenge. In this work, phenolic acids in Spenceria ramalana Trimen and sliver nanoparticle incorporated thermoplastic polyurethane nanofibrous membrane (TPU/AgNPs/TPA) are fabricated via electrospinning. The TPU/AgNPs/TPA membrane exhibits excellent physicochemical properties with uniform morphology, good mechanical capacity, and appropriate hydrophilia providing suitable environment for wound healing. Moreover, the TPU/AgNPs/TPA membrane shows mild antioxidant property and exhibits continuous antibacterial activity against Staphylococcus aureus and Escherichia coli especially against drug-resistant E. coli. The antibacterial efficiency is as high as 99% lasting for 36 h. Furthermore, the TPU/AgNPs/TPA membrane used as wound dressing can accelerate wound healing through downregulating TNF-α and IL-1β and upregulating vascular endothelial growth factor and epidermal growth factor. Therefore, the TPU/AgNPs/TPA membrane presented in this work with good antibacterial activity is an excellent wound dressing and has great potential in wound healing applications to overcome the problem of resistance.

TiO2 supported single Ag atoms nanozyme for elimination of SARS-CoV2

The outbreak of SARS-coronavirus 2 (SARS-CoV2) has become a global health emergency. Although enormous efforts have been made, there is still no effective treatment against the new virus. Herein, a TiO₂ supported single-atom nanozyme containing atomically dispersed Ag atoms (Ag-TiO₂ SAN) is designed to serve as a highly efficient antiviral nanomaterial. Compared with traditional nano-TiO₂ and Ag, Ag-TiO₂ SAN exhibits higher adsorption (99.65%) of SARS-CoV2 pseudovirus. This adsorption ability is due to the interaction between SAN and receptor binding domain (RBD) of spike 1 protein of SARS-CoV2. Theoretical calculation and experimental evidences indicate that the Ag atoms of SAN strongly bind to cysteine and asparagine, which are the most abundant amino acids on the surface of spike 1 RBD. After binding to the virus, the SAN/virus complex is typically phagocytosed by macrophages and colocalized with lysosomes. Interestingly, Ag-TiO₂ SAN possesses high peroxidase-like activity responsible for reactive oxygen species production under acid conditions. The highly acidic microenvironment of lysosomes could favor oxygen reduction reaction process to eliminate the virus. With hACE2 transgenic mice, Ag-TiO₂ SAN showed efficient anti-SARS-CoV2 pseudovirus activity. In conclusion, Ag-TiO₂ SAN is a promising nanomaterial to achieve effective antiviral effects for SARS-CoV2.

Multiomics assessment in Enchytraeus crypticus exposed to Ag nanomaterials (Ag NM300K) and ions (AgNO3) - Metabolomics, proteomics (& transcriptomics)

Silver nanomaterials (AgNMs) are broadly used and among the most studied nanomaterials. The underlying molecular mechanisms (e.g. protein and metabolite response) that precede phenotypical effects have been assessed to a much lesser extent. In this paper, we assess differentially expressed proteins (DEPs) and metabolites (DEMs) by high-throughput (HTP) techniques (HPLC-MS/MS with tandem mass tags, reversed-phase (RP) and hydrophilic interaction liquid chromatography (HILIC) with mass spectrometric detection). In a time series (0, 7, 14 days), the standard soil model Enchytraeus crypticus was exposed to AgNM300K and AgNO₃ at the reproduction EC20 and EC50. The impact on proteins/metabolites was clearly larger after 14 days. NM300K caused more upregulated DEPs/DEMs, more so at the EC20, whereas AgNO₃ caused a dose response increase of DEPs/DEMs. Similar pathways were activated, although often via opposite regulation (up vs down) of DEPs, hence, dissimilar mechanisms underlie the apical observed impact. Affected pathways included e.g. energy and lipid metabolism and oxidative stress. Uniquely affected by AgNO₃ was catalase, malate dehydrogenase and ATP-citrate synthase, and heat shock proteins (HSP70) and ferritin were affected by AgNM300K. The gene expression-based data in Adverse Outcome Pathway was confirmed and additional key events added, e.g. regulation of catalase and heat shock proteins were confirmed to be included. Finally, we observed (as we have seen before) that lower concentration of the NM caused higher biological impact. Data was deposited to ProteomeXchange, identifier PXD024444.

A review of recent and emerging antimicrobial nanomaterials in wastewater treatment applications

In this paper, we present a critical review on antimicrobial nanomaterials with demonstrated potential for application as a disinfection technology in wastewater treatment. Studies involving fabrication and testing of antimicrobial nanomaterials for wastewater treatment were gathered, critically reviewed, and analyzed. Our review shows that there are only a few eligible candidate nanoparticles (NPs) (metal and metal oxide) that can adequately serve as an antimicrobial agent. Nanosilver (nAg) was the most studied and moderately understood metal NPs with proven antimicrobial activity followed by ZnO (among antimicrobial metal oxide NPs) which outperformed titania (in the absence of light) in efficacy due to its better solubility in aqueous condition. The direction of future work was found to be in the development of antimicrobial nanocomposites, since they provide more stability for antimicrobial metal and metal oxides NPs in water, thereby increasing their activity. This review will serve as an updated survey, yet touching also the fundamentals of the antimicrobial activity, with vital information for researchers planning to embark on the development of superior antimicrobial nanomaterials for wastewater treatment applications.

Recent advances in anticancer and antimicrobial activity of silver nanoparticles synthesized using phytochemicals and organic polymers

Development of eco-friendly synthetic methods has resulted in the production of biocompatible Ag NPs for applications in medical sector. To overcome the prevailing antibiotic resistance in bacteria, Ag NPs are being extensively researched over the past few years due to their broad spectrum and robust antimicrobial properties. Silver nanoparticles are also being studied widely in advanced anticancer therapy as an alternative anticancer agent to combat cancer in an effective manner. Keeping this backdrop in consideration, this review aims to provide an extensive coverage of the recent progresses in the green synthesis of Ag NPs specifically using plant derived reducing agents such phytochemicals and numerous other biopolymers. Current development in antimicrobial activity of Ag NPs against various pathogens has been deliberated at length. Recent advances in potent anticancer activity of the biogenic Ag NPs against various cancerous cell lines has also been discussed in detail. Mechanistic details of the synthesis of Ag NPs, their anticancer and antimicrobial action has also been highlighted.

Silver nanoparticles-chitosan composites activity against resistant bacteria: tolerance and biofilm inhibition

This study aimed to evaluate the effectiveness of silver nanoparticles-chitosan composites (AgNPs) with different morphologies and particle size distributions against resistant bacteria and biofilm formation. Four different samples were prepared by a two-step procedure using sodium borohydride and ascorbic acid as reducing agents and characterized by UV-Vis absorption spectra, scanning transmission electron microscopy. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the AgNPs were determined according to the Clinical and Laboratory Standards Institute (CLSI) against clinical isolates multidrug-resistant and strains of the American Type Culture Collection (ATCC). An assay was performed to determine the MICs during 20 successive bacteria exposures to AgNPs to investigate whether AgNPs induce tolerance in bacteria. The antibiofilm activities of AgNPs were also evaluated by determining the minimum biofilm inhibitory concentration (MBIC). The spherical AgNPs present diameters ranging from 9.3 to 62.4 nm, and some samples also have rod-, oval-, and triangle-shaped nanoparticles. The MIC and MBC values ranged from 0.8 to 25 μg/mL and 3.1 to 50 μg/mL, respectively. Smaller and spherical AgNPs exhibited the highest activity, but all the AgNPs developed in this study exhibit bactericidal activity. There was no significant MIC increase after 20 passages to the AgNPs. Regarding the antibiofilm activity, MBICs ranged from 12.5 to 50 μg/mL. Again, smaller and spherical nanoparticles presented the best results with phenotypic inhibition of production of slime or exopolysaccharide (EPS) matrix. Thus, it was concluded that AgNPs have a promising potential against resistant bacteria and bacteria that grow on biofilms without inducing tolerance.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11051-021-05314-1.

Efficacy of green synthesized silver nanoparticles via ginger rhizome extract against Leishmania major in vitro

INTRODUCTION

Leishmaniasis is a major public health problem that causes by parasite of the genus Leishmania. The pentavalent antimonial compounds that used for treatment are not safe or effective enough. The aim of the present study was preparation and evaluation of the efficacy of green synthesized silver nanoparticles against Leishmania major (L. major) in vitro.

METHODS

To synthesis silver (Ag) nanoparticles (NPs), ginger extract was added to the 0.2mM AgNO3 aqueous solution (1:20). Effects of different concentrations of Ag-NPs on the number of L. major promastigotes were investigated using counting assay. The MTT test was applied to determine the toxicity of Ag-NPs on promastigotes of L. major, as well as, macrophage cells. Then, to evaluate the anti-amastigotes effects of Ag-NPs, parasites within the macrophages were counted by light microscope. Furthermore, to determine the induced apoptosis and necrotic effects of Ag-NPs on promastigotes, flow cytometry method was employed using annexin staining.

RESULTS

The effect of Ag-NPs on promastigotes and amastigotes of L. major was effective and has a reverse relationship with its concentration. According to the results of anti-amastigote assay, the IC50 value of this nanoparticle was estimated 2.35 ppm after 72h. Also, Ag-NPs caused Programmed Cell Death (PCD) in promastigotes of L. major and showed 60.18% of apoptosis.

DISCUSSION

Based on the mentioned results, it can be concluded that Ag NPs has a beneficial effect on promastigote and amastigote forms of L. major in vitro. Hence, these nanoparticles could be applied as promising antileishmanial agents for treatment of Leishmania infections.

Development of an anti-infective coating on the surface of intraosseous implants responsive to enzymes and bacteria

Background

Bacterial proliferation on the endosseous implants surface presents a new threat to the using of the bone implants. Unfortunately, there is no effective constructed antibacterial coating which is bacterial anti-adhesion substrate-independent or have long-term biofilm inhibition functions.

Methods

Drug release effect was tested in Chymotrypsin (CMS) solution and S. aureus. We used bacterial inhibition rate assays and protein leakage experiment to analyze the in vitro antibacterial effect of (Montmorillonite/Poly-l-lysine-Chlorhexidine)₁₀ [(MMT/PLL-CHX)₁₀] multilayer film. We used the CCK-8 assay to analyze the effect of (MMT/PLL-CHX)₁₀ multilayer films on the growth and proliferation of rat osteoblasts. Rat orthopaedic implant-related infections model was constructed to test the antimicrobial activity effect of (MMT/PLL-CHX)₁₀ multilayer films in vivo.

Results

In this study, the (MMT/PLL-CHX)₁₀ multilayer films structure were progressively degraded and showed well concentration-dependent degradation characteristics following incubation with Staphylococcus aureus and CMS solution. Bacterial inhibition rate assays and protein leakage experiment showed high levels of bactericidal activity. While the CCK-8 analysis proved that the (MMT/PLL-CHX)₁₀ multilayer films possess perfect biocompatibility. It is somewhat encouraging that in the in vivo antibacterial tests, the K-wires coated with (MMT/PLL-CHX)₁₀ multilayer films showed lower infections incidence and inflammation than the unmodified group, and all parameters are close to SHAM group.

Conclusion

(MMT/PLL-CHX)₁₀ multilayer films provides a potential therapeutic method for orthopaedic implant-related infections.

Platelet membrane-camouflaged silver metal-organic framework drug system against infections caused by methicillin-resistant Staphylococcus aureus

Background

Due to the intelligent survival strategy and self-preservation of methicillin-resistant Staphylococcus aureus (MRSA), many antibiotics are ineffective in treating MRSA infections. Nano-drug delivery systems have emerged as a new method to overcome this barrier. The aim of this study was to construct a novel nano-drug delivery system for the treatment of MRSA infection, and to evaluate the therapeutic effect and biotoxicity of this system. We prepared a nano silver metal-organic framework using 2-methylimidazole as ligand and silver nitrate as ion provider. Vancomycin (Vanc) was loaded with Ag-MOF, and nano-sized platelet vesicles were prepared to encapsulate Ag-MOF-Vanc, thus forming the novel platelet membrane-camouflaged nanoparticles PLT@Ag-MOF-Vanc.

Results

The synthesized Ag-MOF particles had uniform size and shape of radiating corona. The mean nanoparticle size and zeta potential of PLT@Ag-MOF-Vanc were 148 nm and − 25.6 mV, respectively. The encapsulation efficiency (EE) and loading efficiency (LE) of vancomycin were 81.0 and 64.7 %, respectively. PLT@Ag-MOF-Vanc was shown to be a pH-responsive nano-drug delivery system with good biocompatibility. Ag-MOF had a good inhibitory effect on the growth of three common clinical strains (Escherichia coli, Pseudomonas aeruginosa, and S. aureus). PLT@Ag-MOF-Vanc showed better antibacterial activity against common clinical strains in vitro than free vancomycin. PLT@Ag-MOF-Vanc killed MRSA through multiple approaches, including interfering with the metabolism of bacteria, catalyzing reactive oxygen species production, destroying the integrity of cell membrane, and inhibiting biofilm formation. Due to the encapsulation of the platelet membrane, PLT@Ag-MOF-Vanc can bind to the surface of the MRSA bacteria and the sites of MRSA infection. PLT@Ag-MOF-Vanc had a good anti-infective effect in mouse MRSA pneumonia model, which was significantly superior to free vancomycin, and has no obvious toxicity.

Conclusions

PLT@Ag-MOF-Vanc is a novel effective targeted drug delivery system, which is expected to be used safely in anti-infective therapy of MRSA.

Graphic abstract

Antibacterial Properties of a Honeycomb-like Pattern with Cellulose Acetate and Silver Nanoparticles

This study involved the preparation and characterization of structures with a honeycomb-like pattern (HCP) formed using the phase separation method using a solution mixture of chloroform and methanol together with cellulose acetate. Fluorinated ethylene propylene modified by plasma treatment was used as a suitable substrate for the formation of the HCP structures. Further, we modified the HCP structures using silver sputtering (discontinuous Ag nanoparticles) or by adding Ag nanoparticles in PEG into the cellulose acetate solution. The material morphology was then determined using atomic force microscopy (AFM) and scanning electron microscopy (SEM), while the material surface chemistry was studied using energy dispersive spectroscopy (EDS) and wettability was analyzed with goniometry. The AFM and SEM results revealed that the surface morphology of pristine HCP with hexagonal pores changed after additional sample modification with Ag, both via the addition of nanoparticles and sputtering, accompanied with an increase in the roughness of the PEG-doped samples, which was caused by the high molecular weight of PEG and its gel-like structure. The highest amount (approx. 25 at %) of fluorine was detected using the EDS method on the sample with an HCP-like structure, while the lowest amount (0.08%) was measured on the PEG + Ag sample, which revealed the covering of the substrate with biopolymer (the greater fluorine extent means more of the fluorinated substrate is exposed). As expected, the thickness of the Ag layer on the HCP surface depended on the length of sputtering (either 150 s or 500 s). The sputtering times for Ag (150 s and 500 s) corresponded to layers with heights of about 8 nm (3.9 at % of Ag) and 22 nm (10.8 at % of Ag), respectively. In addition, we evaluated the antibacterial potential of the prepared substrate using two bacterial strains, one Gram-positive of S. epidermidis and one Gram-negative of E. coli. The most effective method for the construction of antibacterial surfaces was determined to be sputtering (150 s) of a silver nanolayer onto a HCP-like cellulose structure, which proved to have excellent antibacterial properties against both G+ and G- bacterial strains.

Antibacterial Potential of Biosynthesized Zinc Oxide Nanoparticles against Poultry-Associated Foodborne Pathogens: An In Vitro Study

Simple Summary

The overuse of antibiotics in the poultry industry has led to the emergence of multidrug-resistant microorganisms. Thus, there is a need to find an alternative to conventional antibiotics. Recently, zinc oxide nanoparticles (ZnO NPs) have gained much attention due to their excellent antibacterial activity. In addition, ZnO NPs is an essential trace mineral in poultry diets. In this sense, incorporating ZnO NPs into poultry can promote growth and performance while serving as an alternative antibacterial agent to control diseases. Therefore, this study aimed to assess the in vitro antibacterial activity and antibacterial mechanisms of ZnO NPs against poultry-associated foodborne pathogens (Salmonella spp., Escherichia coli, and Staphylococcus aureus). The obtained findings demonstrated effective antibacterial actions against the tested microorganisms. The nanotechnology approach could represent a new tool for combating pathogens in the poultry industry.

Abstract

Since the emergence of multidrug-resistant bacteria in the poultry industry is currently a serious threat, there is an urgent need to develop a more efficient and alternative antibacterial substance. Zinc oxide nanoparticles (ZnO NPs) have exhibited antibacterial efficacy against a wide range of microorganisms. Although the in vitro antibacterial activity of ZnO NPs has been studied, little is known about the antibacterial mechanisms of ZnO NPs against poultry-associated foodborne pathogens. In the present study, ZnO NPs were successfully synthesized using Lactobacillus plantarum TA4, characterized, and their antibacterial potential against common avian pathogens (Salmonella spp., Escherichia coli, and Staphylococcus aureus) was investigated. Confirmation of ZnO NPs by UV-Visual spectroscopy showed an absorption band center at 360 nm. Morphologically, the synthesized ZnO NPs were oval with an average particle size of 29.7 nm. Based on the dissolution study of Zn²⁺, ZnO NPs released more ions than their bulk counterparts. Results from the agar well diffusion assay indicated that ZnO NPs effectively inhibited the growth of the three poultry-associated foodborne pathogens. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were assessed using various concentrations of ZnO NPs, which resulted in excellent antibacterial activity as compared to their bulkier counterparts. S. aureus was more susceptible to ZnO NPs compared to the other tested bacteria. Furthermore, the ZnO NPs demonstrated substantial biofilm inhibition and eradication. The formation of reactive oxygen species (ROS) and cellular material leakage was quantified to determine the underlying antibacterial mechanisms, whereas a scanning electron microscope (SEM) was used to examine the morphological changes of tested bacteria treated with ZnO NPs. The findings suggested that ROS-induced oxidative stress caused membrane damage and bacterial cell death. Overall, the results demonstrated that ZnO NPs could be developed as an alternative antibiotic in poultry production and revealed new possibilities in combating pathogenic microorganisms.

Silver Nanoparticles and Their Antibacterial Applications

Silver nanoparticles (AgNPs) have been imposed as an excellent antimicrobial agent being able to combat bacteria in vitro and in vivo causing infections. The antibacterial capacity of AgNPs covers Gram-negative and Gram-positive bacteria, including multidrug resistant strains. AgNPs exhibit multiple and simultaneous mechanisms of action and in combination with antibacterial agents as organic compounds or antibiotics it has shown synergistic effect against pathogens bacteria such as Escherichia coli and Staphylococcus aureus. The characteristics of silver nanoparticles make them suitable for their application in medical and healthcare products where they may treat infections or prevent them efficiently. With the urgent need for new efficient antibacterial agents, this review aims to establish factors affecting antibacterial and cytotoxic effects of silver nanoparticles, as well as to expose the advantages of using AgNPs as new antibacterial agents in combination with antibiotic, which will reduce the dosage needed and prevent secondary effects associated to both.

Noncytotoxic silver nanoparticles as a new antimicrobial strategy

Drug-resistance of bacteria is an ongoing problem in hospital treatment. The main mechanism of bacterial virulency in human infections is based on their adhesion ability and biofilm formation. Many approaches have been invented to overcome this problem, i.e. treatment with antibacterial biomolecules, which have some limitations e.g. enzymatic degradation and short shelf stability. Silver nanoparticles (AgNPs) may be alternative to these strategies due to their unique and high antibacterial properties. Herein, we report on yeast Saccharomyces cerevisiae extracellular-based synthesis of AgNPs. Transmission electron microscopy (TEM) revealed the morphology and structure of the metallic nanoparticles, which showed a uniform distribution and good colloid stability, measured by hydrodynamic light scattering (DLS). The energy dispersive X-ray spectroscopy (EDS) of NPs confirms the presence of silver and showed that sulfur-rich compounds act as a capping agent being adsorbed on the surface of AgNPs. Antimicrobial tests showed that AgNPs inhibit the bacteria growth, while have no impact on fungi growth. Moreover, tested NPs was characterized by high inhibitory potential of bacteria biofilm formation but also eradication of established biofilms. The cytotoxic effect of the NPs on four mammalian normal and cancer cell lines was tested through the metabolic activity, cell viability and wound-healing assays. Last, but not least, ability to deep penetration of the silver colloid to the root canal was imaged by scanning electron microscopy (SEM) to show its potential as the material for root-end filling.

Proteomic analysis of an Enterococcus faecalis mutant generated against the exposure to silver nanoparticles

INTRODUCTION

Nanoparticles (NPs) have been widely studied as an alternative to antibiotic use due to their antimicrobial properties at lower concentrations. Enterococcus faecalis is a facultative Gram-positive microorganism inhabiting the gastrointestinal tract of humans and animals. It can also be present in other environments such as the oral cavity, water, sewage, soil and food.

AIMS

We evaluated whether E. faecalis could develop resistance to silver NPs (AgNPs) after exposure to sublethal concentrations of the NPs.

METHODS AND RESULTS

Proteomic analyses revealed that different pathways were activated during the acquired resistance under sublethal concentrations, and selected genes were validated by qPCR.

CONCLUSIONS

The results of this study showed that E. faecalis is capable of generating resistance to AgNPs.

SIGNIFICANCE AND IMPACT OF THE STUDY

To avoid the generation of resistance against AgNPs, future use of these NPs should be combined with other NPs prepared with different metals to prevent the dissemination of resistant strains.

Evaluation of the anti-biofilm effect of poloxamer-based thermoreversible gel of silver nanoparticles as a potential medication for root canal therapy

The purpose of this study was to design silver nanoparticles (AgNPs) poloxamer thermoreversible gel (AgNPs-PL) and investigate whether this gel could provide sustained antibacterial activity against Enterococcus faecalis (E. faecalis) in the root canal. The gels fabricated were characterized in terms of gelatin temperature, particle size, in-vitro Ag⁺ release, and elemental content. Cytotoxicity of AgNPs-PL on primary human periodontal ligament fibroblasts (HPDLFs) was examined by CCK-8 assay. Characterization of AgNPs-PL gel revealed that it contained particles existing as large clumps/fused aggregates of different shapes, with a mean diameter of 21.624 ± 14.689 nm, exhibited sustained release of Ag⁺ for 9 days, and non-toxic to HPDLFs at a low dose (4–32 μg/mL) through 24, 48, and 72 h exposures. The antibacterial effect of 16 and 32 μg/mL concentrations of AgNPs-PL was compared with blank poloxamer gel (PL) and calcium hydroxide (CH) using three methods: (I) agar counting plate, (II) scanning electron microscope (SEM) observations, and (III) confocal laser scanning microscope (CLSM) analysis. AgNPs-PL at the two doses above was more effective than PL and CH in removing E. faecalis biofilm at 1, 3, 9 days. Thus, AgNPs-PL exhibits strong activity against E. faecalis and is easy to produce, with a continuous release profile of Ag⁺. AgNPs-PL gel may be a candidate for a new root canal disinfection.

Molecular Mechanisms of Nanomaterial-Bacterial Interactions Revealed by Omics-The Role of Nanomaterial Effect Level

Nanotechnology is employed across a wide range of antibacterial applications in clinical settings, food, pharmaceutical and textile industries, water treatment and consumer goods. Depending on type and concentration, engineered nanomaterials (ENMs) can also benefit bacteria in myriad contexts including within the human body, in biotechnology, environmental bioremediation, wastewater treatment, and agriculture. However, to realize the full potential of nanotechnology across broad applications, it is necessary to understand conditions and mechanisms of detrimental or beneficial effects of ENMs to bacteria. To study ENM effects, bacterial population growth or viability are commonly assessed. However, such endpoints alone may be insufficiently sensitive to fully probe ENM effects on bacterial physiology. To reveal more thoroughly how bacteria respond to ENMs, molecular-level omics methods such as transcriptomics, proteomics, and metabolomics are required. Because omics methods are increasingly utilized, a body of literature exists from which to synthesize state-of-the-art knowledge. Here we review relevant literature regarding ENM impacts on bacterial cellular pathways obtained by transcriptomic, proteomic, and metabolomic analyses across three growth and viability effect levels: inhibitory, sub-inhibitory or stimulatory. As indicated by our analysis, a wider range of pathways are affected in bacteria at sub-inhibitory vs. inhibitory ENM effect levels, underscoring the importance of ENM exposure concentration in elucidating ENM mechanisms of action and interpreting omics results. In addition, challenges and future research directions of applying omics approaches in studying bacterial-ENM interactions are discussed.

Update on the role of antiseptics in the management of chronic wounds with critical colonisation and/or biofilm

Biofilms play a major role in delaying chronic wounds from healing. A wound infiltrated with biofilm, or "critically colonised" wound, may become clinically infected if the number of microbes exceeds a critical level. Chronic wound biofilms represent a significant treatment challenge by demonstrating recalcitrance towards antimicrobial agents. However, a "window of opportunity" may exist after wound debridement when biofilms are more susceptible to topical antiseptics. Here, we discuss the role of antiseptics in the management of chronic wounds and biofilm, focusing on povidone-iodine (PVP-I) in comparison with two commonly used antiseptics: polyhexanide (PHMB) and silver. This article is based on the literature reviewed during a focus group meeting on antiseptics in wound care and biofilm management, and on a PubMed search conducted in March 2020. Compared with PHMB and silver, PVP-I has a broader spectrum of antimicrobial activity, potent antibiofilm efficacy, no acquired bacterial resistance or cross-resistance, low cytotoxicity, good tolerability, and an ability to promote wound healing. PVP-I represents a viable therapeutic option in wound care and biofilm management, with the potential to treat biofilm-infiltrated, critically colonised wounds. We propose a practical algorithm to guide the management of chronic, non-healing wounds due to critical colonisation or biofilm, using PVP-I.

Nanoparticles as therapeutic options for treating multidrug-resistant bacteria: research progress, challenges, and prospects

Resistance to antimicrobial agents has been alarming in recent years and poses a huge public health threat globally according to the WHO. The increase in morbidity and mortality resulting from microbial infections has been attributed to the emergence of multidrug-resistant microbes. Associated with the increase in multidrug resistance is the lack of new and effective antimicrobials. This has led to global initiatives to identify novel and more effective antimicrobial agents in addition to discovering novel and effective drug delivery and targeting methods. The use of nanoparticles as novel biomaterials to fully achieve this feat is currently gaining global attention. Nanoparticles could become an indispensable viable therapeutic option for treating drug-resistant infections. Of all the nanoparticles, the metals and metal oxide nanoparticles appear to offer the most promise and have attracted tremendous interest from many researchers. Moreover, the use of nanomaterials in photothermal therapy has received considerable attention over the years. This review provides current insight on antimicrobial resistance as well as the mechanisms of nanoparticle antibacterial activity. It offers an in-depth review of all the recent findings in the use of nanomaterials as agents against multi-resistant pathogenic bacteria. Also, nanomaterials that can respond to light stimuli (photothermal therapy) to kill microbes and facilitate enhanced drug delivery and release are discussed. Moreover, the synergistic interactions of nanoparticles with antibiotics and other nanomaterials, microbial adaptation strategies to nanoparticles, current challenges, and future prospects were extensively discussed.

Nanoparticles as therapeutic options for treating multidrug-resistant bacteria: research progress, challenges, and prospects

Resistance to antimicrobial agents has been alarming in recent years and poses a huge public health threat globally according to the WHO. The increase in morbidity and mortality resulting from microbial infections has been attributed to the emergence of multidrug-resistant microbes. Associated with the increase in multidrug resistance is the lack of new and effective antimicrobials. This has led to global initiatives to identify novel and more effective antimicrobial agents in addition to discovering novel and effective drug delivery and targeting methods. The use of nanoparticles as novel biomaterials to fully achieve this feat is currently gaining global attention. Nanoparticles could become an indispensable viable therapeutic option for treating drug-resistant infections. Of all the nanoparticles, the metals and metal oxide nanoparticles appear to offer the most promise and have attracted tremendous interest from many researchers. Moreover, the use of nanomaterials in photothermal therapy has received considerable attention over the years. This review provides current insight on antimicrobial resistance as well as the mechanisms of nanoparticle antibacterial activity. It offers an in-depth review of all the recent findings in the use of nanomaterials as agents against multi-resistant pathogenic bacteria. Also, nanomaterials that can respond to light stimuli (photothermal therapy) to kill microbes and facilitate enhanced drug delivery and release are discussed. Moreover, the synergistic interactions of nanoparticles with antibiotics and other nanomaterials, microbial adaptation strategies to nanoparticles, current challenges, and future prospects were extensively discussed.

Endophytic Nanotechnology: An Approach to Study Scope and Potential Applications

Nanotechnology has become a very advanced and popular form of technology with huge potentials. Nanotechnology has been very well explored in the fields of electronics, automobiles, construction, medicine, and cosmetics, but the exploration of nanotecnology's use in agriculture is still limited. Due to climate change, each year around 40% of crops face abiotic and biotic stress; with the global demand for food increasing, nanotechnology is seen as the best method to mitigate challenges in disease management in crops by reducing the use of chemical inputs such as herbicides, pesticides, and fungicides. The use of these toxic chemicals is potentially harmful to humans and the environment. Therefore, using NPs as fungicides/ bactericides or as nanofertilizers, due to their small size and high surface area with high reactivity, reduces the problems in plant disease management. There are several methods that have been used to synthesize NPs, such as physical and chemical methods. Specially, we need ecofriendly and nontoxic methods for the synthesis of NPs. Some biological organisms like plants, algae, yeast, bacteria, actinomycetes, and fungi have emerged as superlative candidates for the biological synthesis of NPs (also considered as green synthesis). Among these biological methods, endophytic microorganisms have been widely used to synthesize NPs with low metallic ions, which opens a new possibility on the edge of biological nanotechnology. In this review, we will have discussed the different methods of synthesis of NPs, such as top-down, bottom-up, and green synthesis (specially including endophytic microorganisms) methods, their mechanisms, different forms of NPs, such as magnesium oxide nanoparticles (MgO-NPs), copper nanoparticles (Cu-NPs), chitosan nanoparticles (CS-NPs), β-d-glucan nanoparticles (GNPs), and engineered nanoparticles (quantum dots, metalloids, nonmetals, carbon nanomaterials, dendrimers, and liposomes), and their molecular approaches in various aspects. At the molecular level, nanoparticles, such as mesoporous silica nanoparticles (MSN) and RNA-interference molecules, can also be used as molecular tools to carry genetic material during genetic engineering of plants. In plant disease management, NPs can be used as biosensors to diagnose the disease.

Preparation, Biocompatibility and Antitumor Activity of Nanodelivery System Targeting Breast Cancer Base on a Silica Nanoparticle

Background

Breast cancer (BC) is the most common type of cancer among women worldwide, and about 30% of males will have recurrent disease.

Methods

In order to treat recurrent BC, we designed a type of silica nanodelivery system loaded with epirubicin and curcumin (composite nanoparticles, CNPs). To promote CNPs clinical application, the stability, the blood, immune and cell compatibility, skin stimulation experiments, anti-tumor activity in vivo and in vitro were studied.

Results

In our study, the CNPs had a particle size of 73.9 nm and a uniform size and morphology; moreover, they maintained physical and chemical stability in the blood protein environment. Additionally, results showed that nanoparticles had good blood and immune compatibility, and they did not affect intracellular superoxide dismutase (SOD) and intracellular catalase (CAT). Skin stimulation experiments showed that CNPs did not cause any obvious irritative damage to the intact skin of rabbits. In the cytotoxicity study, CNPs showed strongest antitumor activity. The results of cell cycle and apoptosis studies showed that CNPs could mainly induce apoptosis of S and G2/M phase cells. In vivo, CNPs showed strongest aggregation in the tumor after 6 h of tail vein administration, and a large amount of CNPs continued to accumulate in the blood after 12 h of administration, indicating that CNPs had long circulation ability. The in vivo antitumor activities showed that CNPs had the strongest antitumor activity and tumor targeting ability, and hematoxylin-eosin staining of internal organs showed no obvious difference between treatment groups and negative control.

Conclusion

CNPs have an ideal biosafety and therapeutic effect for recurrent BC, and they have potential clinical application value.

Novel Lignin-Capped Silver Nanoparticles against Multidrug-Resistant Bacteria

The emergence of bacteria resistant to antibiotics and the resulting infections are increasingly becoming a public health issue. Multidrug-resistant (MDR) bacteria are responsible for infections leading to increased morbidity and mortality in hospitals, prolonged time of hospitalization, and additional burden to financial costs. Therefore, there is an urgent need for novel antibacterial agents that will both treat MDR infections and outsmart the bacterial evolutionary mechanisms, preventing further resistance development. In this study, a green synthesis employing nontoxic lignin as both reducing and capping agents was adopted to formulate stable and biocompatible silver-lignin nanoparticles (NPs) exhibiting antibacterial activity. The resulting silver-lignin NPs were approximately 20 nm in diameter and did not agglomerate after one year of storage at 4 °C. They were able to inhibit the growth of a panel of MDR clinical isolates, including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, at concentrations that did not affect the viability of a monocyte-derived THP-1 human cell line. Furthermore, the exposure of silver-lignin NPs to the THP-1 cells led to a significant increase in the secretion of the anti-inflammatory cytokine IL-10, demonstrating the potential of these particles to act as an antimicrobial and anti-inflammatory agent simultaneously. P. aeruginosa genes linked with efflux, heavy metal resistance, capsular biosynthesis, and quorum sensing were investigated for changes in gene expression upon sublethal exposure to the silver-lignin NPs. Genes encoding for membrane proteins with an efflux function were upregulated. However, all other genes were membrane proteins that did not efflux metals and were downregulated.

Bacterial Mediated Rapid and Facile Synthesis of Silver Nanoparticles and Their Antimicrobial Efficacy against Pathogenic Microorganisms

In the present study, silver nanoparticles (AgNPs), biosynthesized using culture supernatant of bacterial strain Paenarthrobacter nicotinovorans MAHUQ-43, were characterized and their antimicrobial activity was investigated against both Gram-positive Bacillus cereus and Gram-negative bacteria Pseudomonas aeruginosa. Bacterial-mediated synthesized AgNPs were characterized by UV-Visible (UV-Vis) spectrophotometer, field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) analysis. The UV-Vis spectral analysis showed the absorption maxima at 466 nm which assured the synthesis of AgNPs. The FE-TEM analysis revealed the spherical shape of nanoparticles with the size range from 13 to 27 nm. The EDX and XRD analysis ensured the crystalline nature of biosynthesized AgNPs. The FTIR analysis revealed the involvement of different biomolecules for the synthesis of AgNPs as reducing and capping agents. The bacterial-mediated synthesized AgNPs inhibited the growth of pathogenic strains B. cereus and P. aeruginosa and developed a clear zone of inhibition (ZOI). The MIC and MBC for both pathogens were 12.5 µg/mL and 25 µg/mL, respectively. Moreover, field emission scanning electron microscopy analysis revealed that the synthesized AgNPs can destroy the outer membrane and alter the cell morphology of treated pathogens, leading to the death of cells. This study concludes the eco-friendly, facile and rapid synthesis of AgNPs using P. nicotinovorans MAHUQ-43 and synthesized AgNPs showed excellent antimicrobial activity against both Gram-positive and Gram-negative pathogens.

Disinfectants Used in Stomatology and SARS-CoV-2 Infection

Effective disinfection is a basic procedure in medical facilities, including those conducting dental surgeries, where treatments for tissue discontinuity are also performed, as it is an important element of infection prevention. Disinfectants used in dentistry and dental and maxillofacial surgery include both inorganic (hydrogen peroxide, sodium chlorite-hypochlorite) and organic compounds (ethanol, isopropanol, peracetic acid, chlorhexidine, eugenol). Various mechanisms of action of disinfectants have been reported, which include destruction of the structure of bacterial and fungal cell membranes; damage of nucleic acids; denaturation of proteins, which in turn causes inhibition of enzyme activity; loss of cell membrane integrity; and decomposition of cell components. This article discusses the most important examples of substances used as disinfectants in dentistry and presents the mechanisms of their action with particular focus on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The search was conducted in ScienceDirect, PubMed, and Scopus databases. The interest of scientists in the use of disinfectants in dental practice is constantly growing, which results in the increasing number of publications on disinfection, sterilization, and asepsis. Many disinfectants often possess several of the abovementioned mechanisms of action. In addition, disinfectant preparations used in dental practice either contain one compound or are frequently a mixture of active compounds, which increases their range and effectiveness of antimicrobial action. Currently available information on disinfectants that can be used to prevent SARS-CoV-2 infection in dental practices was summarized.

Facile deposition of biogenic silver nanoparticles on porous alumina discs, an efficient antimicrobial, antibiofilm, and antifouling strategy for functional contact surfaces

Surface modification is an emerging strategy for the design of contact materials. Fabricated alumina discs were functionalized by deposition of biogenic silver nanoparticles. The surfaces were characterized for physico-chemical, antibacterial and antibiofilm properties against microbial pathogens. The surface demonstrated improved hydrophobicity and a surface silver nanoparticle content of 6.4 w%. A reduction of more than 99.9% in CFU mL^-i was observed against the Gram-positive and Gram-negative bacteria tested, with >90% reduction of the fungal isolate. After 4 h, microbial adhesion was reduced by >99.9 and 90% for Escherichia coli and Staphylococcus aureus, respectively. Scanning electron micrographs further revealed a biofilm reduction. Cell viability tests indicated a bioincompatibility higher than 80% with Caco-2 and HaCaT cell lines after 48 h contact. The results suggest that deposition of biogenic silver nanoparticles on the surface of contact materials could be employed as a strategy to prevent biofilm formation.

Silver nanoprisms as plasmonic enhancers applied in the photodynamic inactivation of Staphylococcus aureus isolated from bubaline mastitis

Mastitis is a bacterial infection that affects all lactating mammals, and in dairy cattle, it leads to a reduction in their milk production and, in worse cases, it may lead to animal death. One viable therapeutic modality for overcoming bacterial resistance can be photodynamic inactivation (PDI), a therapeutic modality for bacterial infection treatment. One of the main factors that can lead to an efficient PDI process is the association of metallic nanoparticles in the close vicinity of photosensitizers, which has shown promising results due to localized surface plasmon resonance phenomena. In this work, methylene blue (MB) molecules were associated with Ag prismatic nanoplatelets (AgNPrs) to use as PDI photosensitizer against Staphylococcus aureus isolated from bubaline mastitis. The optical plasmonic activity of AgNPrs was tuned to the MB absorption region (600-700 nm) by inducing their growth into prismatic shapes by a seed-mediated procedure, using poly (sodium 4-styrene sulfonate) as the surfactant. A simulation on the plasmonic properties of the nanoprisms, applying particle size within the dimensions determined by TEM image analysis (d = 32 ± 6 nm), showed a 30 % increase of the incident field on the prismatic tips. Photodynamic results showed that the electrostatic AgNPr-MB conjugates promoted enhancement (ca. 15 %) of the reactive oxygen species production. Besides, PDI mediated by AgNPrs-MB led to the complete inactivation of the mastitis S. aureus strain after 6 min inactivation, in contrast to PDI mediated by MB, which reduced less than a 0.5 bacterial log. Thus, the results show this plasmonic enhanced photodynamic tool's potential to be applied in the inactivation of multi-resistant bacterial strains.

Rational Optimization of 1,2,3-Triazole-Tailored Carbazoles As Prospective Antibacterial Alternatives with Significant In Vivo Control Efficiency and Unique Mode of Action

Plant bacterial diseases can potentially damage agricultural products around the world, and few effective bactericides can manage these infections. Herein, to sequentially explore highly effective antibacterial alternatives, 1,2,3-triazole-tailored carbazoles were rationally fabricated. These compounds could suppress the growth of three main intractable pathogens including Xanthomonas oryzae pv oryzae (Xoo), X. axonopodis pv citri (Xac), and Pseudomonas syringae pv actinidiae (Psa) with lower EC₅₀ values of 3.36 (3p), 2.87 (3p), and 4.57 μg/mL (3r), respectively. Pot experiments revealed that compound 3p could control the rice bacterial blight with protective and curative efficiencies of 53.23% and 50.78% at 200 μg/mL, respectively. Interestingly, the addition of 0.1% auxiliaries such as organic silicon and orange oil could significantly enhance the surface wettability of compound 3p toward rice leaves, resulting in improved control effectiveness of 65.50% and 61.38%, respectively. Meanwhile, compound 3r could clearly reduce the white pyogenic exudates triggered by Psa infection and afforded excellent control efficiencies of 79.42% (protective activity) and 78.74% (curative activity) at 200 μg/mL, which were quite better than those of commercial pesticide thiodiazole copper. Additionally, a plausible apoptosis mechanism for the antibacterial behavior of target compounds was proposed by flow cytometry, reactive oxygen species detection, and defensive enzyme (e.g., catalase and superoxide dismutase) activity assays. The current work can promote the development of 1,2,3-triazole-tailored carbazoles as prospective antibacterial alternatives bearing an intriguing mode of action.

Toxic and Microbiological Effects of Iron Oxide and Silver Nanoparticles as Additives on Extended Ram Semen

The aim of the study was to investigate the effect of iron oxide (Fe) and silver (Ag) nanoparticles (NPs) on ram semen. A skim milk extender without antibiotics was used as a diluent of 21 ejaculates (8 rams; 2-3 ejaculates/ram). The groups of control (C; semen without NPs), Fe NPs (3.072 mg Fe₃O₄/mL semen), and Ag NPs (2.048 mg Ag-Fe/mL semen) were incubated (15 °C; 30 min), and then a magnetic field was used for NPs' removal. Standard microbiological procedures were performed for all groups. Post-treated samples were stored (15 °C) for 24 h, and sperm variables (kinetics by computer assisted sperm analysis (CASA); viability; morphology; HOST; DNA integrity) were evaluated at 6 and 24 h. Semen data were analyzed by a mixed model for repeated measures and microbiological data with Student's t-test for paired samples. At 6 h of storage, VCL and rapid movement-spermatozoa, and at 24 h, total/progressive motility and amplitude of lateral head displacement (ALH) were significantly decreased in group Ag compared to control. In group Fe, progressive/rapid movement-spermatozoa were significantly lower compared to control after 24 h of storage. Only in group Ag was a significant reduction of total bacterial count revealed. In conclusion, the examined Fe NPs demonstrated slight antibacterial effect, while the examined Ag NPs provided higher antibacterial properties accompanied by cytotoxicity.

Subinhibitory Concentrations of Biogenic Silver Nanoparticles Affect Motility and Biofilm Formation in Pseudomonas aeruginosa

Biogenic silver nanoparticles (bio-AgNPs) are increasingly recognized as an antibiofilm and antivirulence strategy against P. aeruginosa, a bacterium that causes chronic infections in immunocompromised and cystic fibrosis patients. This study aimed to investigate the effects of subinhibitory concentrations of bio-AgNPs on motility and biofilm formation in P. aeruginosa. Bio-AgNPs were synthesized via reduction of ionic silver catalyzed by cell-free culture filtrate from Fusarium oxysporum. A total of 17 P. aeruginosa isolates and strains were evaluated for swarming, swimming, and twitching motility in the presence and absence (control) of bio-AgNPs, including 10 clinical isolates from patients with and without cystic fibrosis, 5 environmental isolates obtained from the public water supply system, and 2 reference strains (PAO1 and PA14). Isolates were identified by biochemical and molecular methods. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. Swarming, swimming, and twitching motility assays were performed in Petri dishes. Biofilm formation capacity was assessed quantitatively by the crystal violet method. MIC values ranged from 15.62 to 62.50 µM. The results showed that subinhibitory concentrations of bio-AgNPs (½ MIC, 7.81-31.25 µM) significantly increased (p < 0.05) swarming, swimming, and twitching motility in 40.0, 40.0, and 46.7% of isolates, respectively. Subinhibitory bio-AgNP treatment enhanced (p < 0.05) biofilm formation capacity in PA14 and a cystic fibrosis isolate (P11). It is concluded that subinhibitory concentrations of bio-AgNPs increased biofilm formation and swarming, swimming, and twitching motility in PA14 and some P. aeruginosa isolates. These virulence factors are directly involved with quorum-sensing systems. Further research should investigate the effects of AgNPs on P. aeruginosa quorum sensing to help elucidate their mechanism of action at subinhibitory concentrations.

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.

Green synthesized Silver Nanoparticles as Silver Lining in Antimicrobial Resistance: A Review

Unprincipled use of antibiotics has led to the antimicrobial resistance (AMR) against mostly available compounds and now become a major cause of concern for the scientific community. However, in the past decade, green synthesized silver nanoparticles (AgNPs) have received greater attention for the development of newer therapies as antimicrobials by virtue of their unique physico-chemical properties. Unlike traditional antibiotics, AgNPs exert their action by acting on multiple mechanisms which make them potential candidates against AMR. Green synthesis of AgNPs using various medicinal plants has demonstrated broader spectrum of action against several microbes in a number of attempts. The present paper provides an insight into the scientific studies that have elucidated the positive role of plant extracts/phytochemicals during green synthesis of AgNPs and their future perspectives. The studies conducted so far seem promising still, a few factors like, the precise mechanism of action of AgNPs, their synergistic interaction with biomolecules, and industrial scalability need to be explored further till effective drug development using green synthesized AgNPs in healthcare systems against AMR is established.

Cocktail Therapy of Fosthiazate and Cupric-Ammoniun Complex for Citrus Huanglongbing

Huanglongbing (HLB) is a destructive citrus bacterial disease caused by Candidatus Liberibacter asiaticus (Ca.Las) and cannot be cured by current pesticides. Root lesion and Tylenchulus semipenetrans juveniles were observed in HLB-affected citrus tree roots. We hypothesize that root treatment with fosthiazate (FOS) and Cupric-Ammonium Complex (CAC) will improve the root growth and inhibit HLB. CAC is a broad spectrum fungicide and can promote growth of crops. FOS kills Tylenchulus semipenetrans and protects roots from damage by harmful bacteria such as Ca.Las. After 90 days of combination treatment of FOS and CAC through root drenches, the citrus grew new roots and its leaves changed their color to green. The inhibition rate of Ca.Las reached more than 90%. During treatment process, the chlorophyll content and the root vitality increased 396 and 151%, respectively, and starch accumulation decreased by 88%. Transmission electron microscopy (TEM) and plant tissue dyeing experiments showed that more irregular swollen starch granules existed in the chloroplast thylakoid system of the HLB-infected leaves. This is due to the blocking of their secretory tissue by starch. TEM and flow cytometry experiments in vitro showed the synergistic effects of FOS and CAC. A transcriptome analysis revealed that the treatment induced the differential expression of the genes which involved 103 metabolic pathways. These results suggested that the cocktail treatment of FOS and CAC may effectively kill various pathogens including Ca.Las on citrus root and thus effectively control HLB.

Green Synthesis of Silver Nanoparticles Using the Lotus lalambensis Aqueous Leaf Extract and Their Anti-Candidal Activity against Oral Candidiasis

Oral candidiasis is widely spread in both humans and animals, which is caused mainly by Candida albicans. In this study, we aimed to biosynthesize silver nanoparticles (AgNPs) for the first time using the Lotus lalambensis Schweinf leaf extract (L-AgNPs) and investigated their anti-candidal potency alone or in combination with the leaf extract of L. lalambensis (L-AgNPs/LL) against C. albicans. The biosynthesized L-AgNPs were characterized by imaging (transmission electron microscopy, TEM), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results of the disk diffusion method showed the potent synergistic anti-candidal activity of L-AgNPs/LL (24 mm inhibition zone). L-AgNPs/LL completely inhibited the morphogenesis of C. albicans and suppressed the adhesion and the formation of the biofilm of C. albicans by 82.5 and 78.7%, respectively. Further, L-AgNPs/LL inhibited the production of antioxidant enzymes of C. albicans by 80%. SEM and TEM revealed deteriorations in the cell wall ultrastructure in L-AgNPs/LL-treated C. albicans. Interestingly, L-AgNPs/LL showed less than 5% cytotoxicity when examined with either the primary bone marrow derived mesenchymal stem cell (BMSCs) or MCF-7 cell line at MIC values of L-AgNPs/LL. In conclusion, we identified L-AgNPs/LL as a potential biosynthesized-based drug for oral candidiasis in humans and animals.

Comparison of Two Transmission Electron Microscopy Methods to Visualize Drug-Induced Alterations of Gram-Negative Bacterial Morphology

In this study, we optimized and compared different transmission electron microscopy (TEM) methods to visualize changes to Gram-negative bacterial morphology induced by treatment with a robenidine analogue (NCL195) and colistin combination. Aldehyde-fixed bacterial cells (untreated, treated with colistin or NCL195 + colistin) were prepared using conventional TEM methods and compared with ultrathin Tokuyasu cryo-sections. The results of this study indicate superiority of ultrathin cryo-sections in visualizing the membrane ultrastructure of Escherichia coli and Pseudomonas aeruginosa, with a clear delineation of the outer and inner membrane as well as the peptidoglycan layer. We suggest that the use of ultrathin cryo-sectioning can be used to better visualize and understand drug interaction mechanisms on the bacterial cell membrane.

Novel Strategy to Combat Antibiotic Resistance: A Sight into the Combination of CRISPR/Cas9 and Nanoparticles

Antibiotic resistance is a significant crisis that threatens human health and safety worldwide. There is an urgent need for new strategies to control multidrug-resistant (MDR) bacterial infections. The latest breakthrough in gene-editing tools based on CRISPR/Cas9 has potential application in combating MDR bacterial infections because of their high targeting ability to specifically disrupt the drug resistance genes that microbes use for infection or to kill the pathogen directly. Despite the potential that CRISPR/Cas9 showed, its further utilization has been hampered by undesirable delivery efficiency in vivo. Nanotechnology offers an alternative way to overcome the shortcomings of traditional delivery methods of therapeutic agents. Advances in nanotechnology can improve the efficacy and safety of CRISPR/Cas9 components by using customized nanoparticle delivery systems. The combination of CRISPR/Cas9 and nanotechnology has the potential to open new avenues in the therapy of MDR bacterial infections. This review describes the recent advances related to CRISPR/Cas9 and nanoparticles for antimicrobial therapy and gene delivery, including the improvement in the packaging and localizing efficiency of the CRISPR/Cas9 components in the NP (nanoparticle)/CRISPR system. We pay particular attention to the strengths and limitations of the nanotechnology-based CRISPR/Cas9 delivery system to fight nosocomial pathogens.We highlight the need for more scientific research to explore the combinatorial efficacy of various nanoparticles and CRISPR technology to control and prevent antimicrobial resistance.

All That Glitters Is Not Silver-A New Look at Microbiological and Medical Applications of Silver Nanoparticles

Silver and its nanoparticles (AgNPs) have different faces, providing different applications. In recent years, the number of positive nanosilver applications has increased substantially. It has been proven that AgNPs inhibit the growth and survival of bacteria, including human and animal pathogens, as well as fungi, protozoa and arthropods. Silver nanoparticles are known from their antiviral and anti-cancer properties; however, they are also very popular in medical and pharmaceutical nanoengineering as carriers for precise delivery of therapeutic compounds, in the diagnostics of different diseases and in optics and chemistry, where they act as sensors, conductors and substrates for various syntheses. The activity of AgNPs has not been fully discovered; therefore, we need interdisciplinary research to fulfil this knowledge. New forms of products with silver will certainly find application in the future treatment of many complicated and difficult to treat diseases. There is still a lack of appropriate and precise legal condition regarding the circulation of nanomaterials and the rules governing their safety use. The relatively low toxicity, relative biocompatibility and selectivity of nanoparticle interaction combined with the unusual biological properties allow their use in animal production as well as in bioengineering and medicine. Despite a quite big knowledge on this topic, there is still a need to organize the data on AgNPs in relation to specific microorganisms such as bacteria, viruses or fungi. We decided to put this knowledge together and try to show positive and negative effects on prokaryotic and eukaryotic cells.

Binary Medical Nanofluids by Combination of Polymeric Eudragit Nanoparticles for Vehiculization of Tobramycin and Resveratrol: Antimicrobial, Hemotoxicity and Protein Corona Studies

The development of smart nanoparticles (NPs) became a trend to enhance the delivery of drugs. In the present work, Tobramycin (TB), an aminoglycoside antibiotic that displays several undesirable side effects, has been encapsulated into cationic Eudragit®E100 (E100) NPs for the treatment of infections caused by Pseudomonas aeruginosa. Combination with neutral Eudragit®NE30D (NE30D) NPs containing resveratrol (RSV), a strong natural antioxidant, increased the antimicrobial activity of TB (75% higher than free TB). NPs were stabilized with 1.0% (w/v) poloxamer 188 (P188) or poloxamer 407 (P407) as surfactants. E100 NPs showed 83.3 ± 8.5%, and 70.1 ± 2.7 encapsulation efficiency (EE) of TB with P188 and P407 coatings, respectively. The presence of NPs was confirmed by DLS and TEM studies. TB was controlled released from NPs for 6 h. Hemotoxicity tests of NPs in the range of MIC values on human blood gave negative results. Analysis of Surface Plasmon Resonance verified that NE30D/P407/RSV does not interact with plasma proteins BSA, IgG or fibrinogen, besides E100/P188/TB interact with BSA, findings that are compatible with a negligible in vivo clearance of the nanovehicles. The obtained results show a potential binary fluid composed of two NPs to highly improve the effectiveness of conventional antibiotics.

New Textile for Personal Protective Equipment—Plasma Chitosan/Silver Nanoparticles Nylon Fabric

Fabric structures are prone to contamination with microorganisms, as their morphology and ability to retain moisture creates a proper environment for their growth. In this work, a novel, easily processed and cheap coating for a nylon fabric with antimicrobial characteristics was developed. After plasma treatment, made to render the fabric surface more reactive sites, the fabric was impregnated with chitosan and silver nanoparticles by simply dipping it into a mixture of different concentrations of both components. Silver nanoparticles were previously synthesized using the Lee–Meisel method, and their successful obtention was proven by UV–Vis, showing the presence of the surface plasmon resonance band at 410 nm. Nanoparticles with 25 nm average diameter observed by STEM were stable, mainly in the presence of chitosan, which acted as a surfactant for silver nanoparticles, avoiding their aggregation. The impregnated fabric possessed bactericidal activity higher for Gram-positive Staphylococcus aureus than for Gram-negative Pseudomonas aeruginosa bacteria for all combinations. The percentage of live S. aureus and P. aeruginosa CFU was reduced to less than 20% and 60%, respectively, when exposed to each of the coating combinations. The effect was more pronounced when both chitosan and silver were present in the coating, suggesting an effective synergy between these components. After a washing process, the antimicrobial effect was highly reduced, suggesting that the coating is unstable after washing, being almost completely removed from the fabric. Nevertheless, the new-coated fabric can be successfully used in single-use face masks. To our knowledge, the coating of nylon fabrics intended for face-mask material with both agents has never been reported.

Differential effect of silver nanoparticles on the microbiome of adult and developing planaria

Silver nanoparticles (AgNPs) are widely incorporated in household, consumer and medical products. Their unintentional release via wastewaters raises concerns on their environmental impact, particularly for aquatic organisms and their associated bacterial communities. It is known that the microbiome plays an important role in its host's health and physiology, e.g. by producing essential nutrients and providing protection against pathogens. A thorough understanding of the effects of AgNPs on bacterial communities and on their interactions with the host is crucial to fully assess AgNP toxicity on aquatic organisms. Our results indicate that the microbiome of the invertebrate Schmidtea mediterranea, a freshwater planarian, is affected by AgNP exposure at the tested 10 μg/ml concentration. Using targeted amplification of the bacterial 16S rRNA gene V3-V4 region, two independent experiments on the microbiomes of adult worms revealed a consistent decrease in Betaproteobacteriales after AgNP exposure, mainly attributed to a decrease in Curvibacter and Undibacterium. Although developing tissues and organisms are known to be more sensitive to toxic compounds, three independent experiments in regenerating worms showed a less pronounced effect of AgNP exposure on the microbiome, possibly because underlying bacterial community changes during development mask the AgNP induced effect. The presence of a polyvinyl-pyrrolidone (PVP) coating did not significantly alter the outcome of the experiments compared to those with uncoated particles. The observed variation between the different experiments underlines the highly variable nature of microbiomes and emphasises the need to repeat microbiome experiments, within and between physiological states of the animal.

Antimicrobial activity of silver-carbon nanoparticles on the bacterial flora of bull semen

The spermicidal effects of silver nanoparticles (AgNPs) hinder its application in the field of artificial insemination. In this study, silver-carbon NPs (Ag@C NPs) was synthesized and applied as an alternative antibiotic agent for bull semen extender. Ag@C NPs were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption flame spectroscopy, transmission electron microscope (TEM), and high-resolution TEM (HR-TEM). Data analysis revealed the successful synthesis of Ag@C NPs with a particle size of 1-5 nm (average particle size of 2.5 nm) embedded into carbon. The antimicrobial activity of Ag@C NPs was tested against bacteriospermia of fresh semen collected from five fertile bulls (three ejaculates/bull). Escherichia coli (E. Coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) were isolated from fresh semen samples and identified by culture, staining, and conventional biochemical tests. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Ag@C NPs against bacteriospermia was determined at 5 and 37 °C. Ag@C NPs showed efficient antimicrobial activity (MIC: 3.125-12.5 μg/mL) against the tested strains and strong bactericidal effect on S. aureus, and P. aeruginosa (MBC: 3.125 μg/mL), with no detrimental effect (P ˃ 0.05) on the percentage of sperm motility (70.71 ± 4.82; 74.65 ± 4.46), plasma membrane integrity (68.39 ± 4.31; 72.38 ± 4.91), acrosome integrity (88.40 ± 13.21; 86.77 ± 14.23), and normal sperm morphology (86.85 ± 7.43; 87.82 ± 8.15) at concentrations of 15 and 30 μg/mL, respectively, after a cold storage of 48 h. However, Ag@C NPs showed a detrimental effect on sperm parameters in a dose dependent manner at concentrations ≥60 μg/mL. Ag@C NPs showed no adverse effect on the sperm's ultrastructure with limited sperm internalization at MIC. In conclusion, Ag@C NPs could be used as an alternative antibiotic agent for bull semen extender without a significant cytotoxic effect on the sperm during cold storage. However, further investigations for their effects on embryo production and female genitalia are still required.