Mechanistic Insights into the Antimicrobial Actions of Metallic Nanoparticles and Their Implications for Multidrug Resistance

Metallic Nanosystems in the Development of Antimicrobial Strategies with High Antimicrobial Activity and High Biocompatibility

Antimicrobial resistance is a major and growing global problem and new approaches to combat infections caused by antibiotic resistant bacterial strains are needed. In recent years, increasing attention has been paid to nanomedicine, which has great potential in the development of controlled systems for delivering drugs to specific sites and targeting specific cells, such as pathogenic microbes. There is continued interest in metallic nanoparticles and nanosystems based on metallic nanoparticles containing antimicrobial agents attached to their surface (core shell nanosystems), which offer unique properties, such as the ability to overcome microbial resistance, enhancing antimicrobial activity against both planktonic and biofilm embedded microorganisms, reducing cell toxicity and the possibility of reducing the dosage of antimicrobials. The current review presents the synergistic interactions within metallic nanoparticles by functionalizing their surface with appropriate agents, defining the core structure of metallic nanoparticles and their use in combination therapy to fight infections. Various approaches to modulate the biocompatibility of metallic nanoparticles to control their toxicity in future medical applications are also discussed, as well as their ability to induce resistance and their effects on the host microbiome.

Metal Nanoparticles to Combat Candida albicans Infections: An Update

Candidiasis is an opportunistic mycosis with high annual incidence worldwide. In these infections, Candida albicans is the chief pathogen owing to its multiple virulence factors. C. albicans infections are usually treated with azoles, polyenes and echinocandins. However, these antifungals may have limitations regarding toxicity, relapse of infections, high cost, and emergence of antifungal resistance. Thus, the development of nanocarrier systems, such as metal nanoparticles, has been widely investigated. Metal nanoparticles are particulate dispersions or solid particles 10-100 nm in size, with unique physical and chemical properties that make them useful in biomedical applications. In this review, we focus on the activity of silver, gold, and iron nanoparticles against C. albicans. We discuss the use of metal nanoparticles as delivery vehicles for antifungal drugs or natural compounds to increase their biocompatibility and effectiveness. Promisingly, most of these nanoparticles exhibit potential antifungal activity through multi-target mechanisms in C. albicans cells and biofilms, which can minimize the emergence of antifungal resistance. The cytotoxicity of metal nanoparticles is a concern, and adjustments in synthesis approaches or coating techniques have been addressed to overcome these limitations, with great emphasis on green synthesis.

A review: strategies to reduce infection in tantalum and its derivative applied to implants

Implant-associated infection is the main reasons for implant failure. Titanium and titanium alloy are currently the most widely used implant materials. However, they have limited antibacterial performance. Therefore, enhancing the antibacterial ability of implants by surface modification technology has become a trend of research. Tantalum is a potential implant coating material with good biological properties. With the development of surface modification technology, tantalum coating becomes more functional through improvement. In addition to improving osseointegration, its antibacterial performance has also become the focus of attention. In this review, we provide an overview of the latest strategies to improve tantalum antibacterial properties. We demonstrate the potential of the clinical application of tantalum in reducing implant infections by stressing its advantageous properties.

Synthesis and characterization of Ag2O, CoFe2O4, GO, and their ternary composite for antibacterial activity

Currently, nanomaterials with exceptional antibacterial activity have become an emerging domain in research. The optimization of nanomaterials against infection causing agents is the next step in dealing with the present-day problem of antibiotics. In this research work, Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO are prepared by chemical methods. Ag₂O was prepared by co-precipitation method, while solvothermal technique was utilized for the synthesis of CoFe₂O₄. The ternary nanocomposite was synthesized by a simple in situ reduction using a two-step approach. The structural and morphological properties were studied by UV-Vis spectroscopy, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (SEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). From the X-ray diffraction analysis, the crystallite size is found to be 14 nm, 5 nm, and 6 nm for Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO respectively. The synthesized nanomaterials were investigated for antibacterial activities against gram-positive strain Staphylococcus aureus (S. aureus) and gram-negative strain Escherichia coli (E. coli) using Agar well diffusion method. Ag₂O and CoFe₂O₄ showed zones of inhibition (ZOI) of 13 mm and 11 mm against gram positive bacteria while 12 mm against gram negative bacteria respectively, while ternary nanocomposite showed 14 mm and 13 mm of ZOI. The antibacterial activity of nanomaterials showed a gradual increment with an increase in the concentration of the materials. Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO showed minimum inhibitory concentration (MIC) values of 4.5, 6.5, and 4.5 μg/mL for S. aureus and 6.5, 7.2, and 4.8 μg/mL for E. coli respectively. Minimum bactericidal concentrations were found to be same as the MIC values. Additionally, a time-kill curve analysis was performed and for ternary nanocomposite; the killing response was most effective as the complete killing was achieved at 3 h of incubation at 3-MIC (9.75 μg/mL). These results demonstrate that all the nanomaterials, as a kind of antibacterial material, have a great potential for a wide range of biomedical applications.

Influence of biosynthesized nanoparticles exposure on mortality, residual deposition, and intestinal bacterial dysbiosis in Cyprinus carpio

Nanotechnology has revealed profound possibilities for the applications in applied sciences. The nanotechnology works based on nanoparticles. Among nanoparticles, silver nanoparticles largely introduced into aquatic environments during fabrication. Which cause severe contamination in the environment specially in freshwater fish. Therefore, the current study was a pioneer attempt to use the animal blood to fabricate AgNPs and investigate their toxicity in Cyprinus carpio (C. carpio) by recording mortality, tissue bioaccumulation, and influence on intestinal bacterial diversity. For this purpose, fish groups were exposed to different concentrations of B-AgNPs including 0.03, 0.06, and 0.09 mg/L beside the control group for 1, 10, and 20 days. Initially, the highest concentration caused mortality. The results revealed that B-AgNPs were significantly (p < 0.005) accumulated in the liver followed by intestines, gills, and muscles. In addition, the accumulation of B-AgNPs in the intestine led to bacterial dysbiosis in Cyprinus carpio. At the phylum level, Tenericutes, Bacteroidetes, and Planctomycetes were gradually decreased at the highest concentration of B-AgNPs (0.09 mg/L) on days 1, 10, and 20 days. The genera Cetobacterium and Luteolibactor were increased at the highest concentration on day 20. Moreover, the principal coordinate analysis (PCoA) based on Bray-Curtis showed that the B-AgNPs had led to a variation in the intestinal bacterial community. Based on findings, the B-AgNPs induced mortality, and residual deposition in different tissues, and had a stress influence on intestinal homeostasis by affecting the intestinal bacterial community in C. carpio which could have a significant effect on fish growth.

Antibacterial Pathways in Transition Metal-Based Nanocomposites: A Mechanistic Overview

Across the planet, outbreaks of bacterial illnesses pose major health risks and raise concerns. Photodynamic, photothermal, and metal ion release effects of transition metal-based nanocomposites (TMNs) were recently shown to be highly effective in reducing bacterial resistance and upsurges in outbreaks. Surface plasmonic resonance, photonics, crystal structures, and optical properties of TMNs have been used to regulate metal ion release, produce oxidative stress, and generate heat for bactericidal applications. The superior properties of TMNs provide a chance to investigate and improve their antimicrobial actions, perhaps leading to therapeutic interventions. In this review, we discuss three alternative antibacterial strategies based on TMNs of photodynamic therapy, photothermal therapy, and metal ion release and their mechanistic actions. The scientific community has made significant efforts to address the safety, effectiveness, toxicity, and biocompatibility of these metallic nanostructures; significant achievements and trends have been highlighted in this review. The combination of therapies together has borne significant results to counter antimicrobial resistance (4-log reduction). These three antimicrobial pathways are separated into subcategories based on recent successes, highlighting potential needs and challenges in medical, environmental, and allied industries.

The progress in titanium alloys used as biomedical implants: From the view of reactive oxygen species

Titanium and Titanium alloys are widely used as biomedical implants in oral and maxillofacial surgery, due to superior mechanical properties and biocompatibility. In specific clinical populations such as the elderly, diabetics and patients with metabolic diseases, the failure rate of medical metal implants is increased significantly, putting them at increased risk of revision surgery. Many studies show that the content of reactive oxygen species (ROS) in the microenvironment of bone tissue surrounding implant materials is increased in patients undergoing revision surgery. In addition, the size and shape of materials, the morphology, wettability, mechanical properties, and other properties play significant roles in the production of ROS. The accumulated ROS break the original balance of oxidation and anti-oxidation, resulting in host oxidative stress. It may accelerate implant degradation mainly by activating inflammatory cells. Peri-implantitis usually leads to a loss of bone mass around the implant, which tends to affect the long-term stability and longevity of implant. Therefore, a great deal of research is urgently needed to focus on developing antibacterial technologies. The addition of active elements to biomedical titanium and titanium alloys greatly reduce the risk of postoperative infection in patients. Besides, innovative technologies are developing new biomaterials surfaces conferring anti-infective properties that rely on the production of ROS. It can be considered that ROS may act as a messenger substance for the communication between the host and the implanted material, which run through the entire wound repair process and play a role that cannot be ignored. It is necessary to understand the interaction between oxidative stress and materials, the effects of oxidative stress products on osseointegration and implant life as well as ROS-induced bactericidal activity. This helps to facilitate the development of a new generation of well-biocompatible implant materials with ROS responsiveness, and ultimately prolong the lifespan of implants.

Application of Peptides in Construction of Nonviral Vectors for Gene Delivery

Gene therapy, which aims to cure diseases by knocking out, editing, correcting or compensating abnormal genes, provides new strategies for the treatment of tumors, genetic diseases and other diseases that are closely related to human gene abnormalities. In order to deliver genes efficiently to abnormal sites in vivo to achieve therapeutic effects, a variety of gene vectors have been designed. Among them, peptide-based vectors show superior advantages because of their ease of design, perfect biocompatibility and safety. Rationally designed peptides can carry nucleic acids into cells to perform therapeutic effects by overcoming a series of biological barriers including cellular uptake, endosomal escape, nuclear entrance and so on. Moreover, peptides can also be incorporated into other delivery systems as functional segments. In this review, we referred to the biological barriers for gene delivery in vivo and discussed several kinds of peptide-based nonviral gene vectors developed for overcoming these barriers. These vectors can deliver different types of genetic materials into targeted cells/tissues individually or in combination by having specific structure-function relationships. Based on the general review of peptide-based gene delivery systems, the current challenges and future perspectives in development of peptidic nonviral vectors for clinical applications were also put forward, with the aim of providing guidance towards the rational design and development of such systems.

Metallic and non-metallic nanoparticles from plant, animal, and fisheries wastes: potential and valorization for application in agriculture

Global agriculture is facing tremendous challenges due to climate change. The most predominant amongst these challenges are abiotic and biotic stresses caused by increased incidences of temperature extremes, drought, unseasonal flooding, and pathogens. These threats, mostly due to anthropogenic activities, resulted in severe challenges to crop and livestock production leading to substantial economic losses. It is essential to develop environmentally viable and cost-effective green processes to alleviate these stresses in the crops, livestock, and fisheries. The application of nanomaterials in farming practice to minimize nutrient losses, pest management, and enhance stress resistance capacity is of supreme importance. This paper explores innovative methods for synthesizing metallic and non-metallic nanoparticles using plants, animals, and fisheries wastes and their valorization to mitigate abiotic and biotic stresses and input use efficiency in climate-smart and stress-resilient agriculture including crop plants, livestock, and fisheries.

Green synthesis of silver nanoparticles from Mahonia fortunei extracts and characterization of its inhibitory effect on Chinese cabbage soft rot pathogen

The pathogenic bacterium Pectobacterium carotovorum causes soft rot in cabbage and significantly reduces plant yield. In this study, we employed Mhonia fortunei extracts to synthesis silver nanoparticles (Mf-AgNPs) and investigated their functions against P. carotovorum. The results showed that the surface plasmon resonance (SPR) peak of AgNP was 412 nm under optimal synthesis conditions. Furthermore, the results of Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS) and High-resolution transmission electron microscopy (HR-TEM) revealed that the Mf-AgNPs had a spherical structure with an average diameter of 13.19 nm and the content of Ag0 ions accounted for 82.68% of the total elemental content. The X-Ray diffraction (XRD) results confirmed that AgNPs had a face-centered cubic (FCC) crystal structure, while Fourier transform infrared spectroscopy (FTIR) results indicated the presence of various biomolecules as reducing and stabilizing agents on the AgNP surface. Antibacterial activity was first evaluated by an inhibitory zone test, which revealed that 500 μg ml⁻¹ of AgNPs had antibacterial activity against P. carotovorum and four model bacteria including Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa, respectively with an antibacterial function comparable to 1 mM AgNO₃ solution. The Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for P. carotovorum were 8 μg ml⁻¹, respectively. Furthermore, AgNPs at 8 μg ml⁻¹ completely inhibited the growth of P. carotovorum, decreased their tolerance to 0.25 mM H₂O₂ as well as considerably reduced colony formation after 1 h of treatment and thereafter. Treatment with Mf-AgNPs resulted in bacterial cell membrane destruction and biofilm formation inhibition, respectively. With an FIC (fractional inhibitory concentration) index of 0.174, AgNP and zhongshengmycin showed a significant synergistic effect. The infection of P. carotovorum to cabbage explants was significantly inhibited in vitro by a combination of 2 μg ml⁻¹ Mf-AgNP and 5 μg ml⁻¹ zhongshengmycin. In conclusion, the synthesized Mf-AgNP exhibited significant antibacterial activity against P. carotovorum.

Photocatalytic and Antibacterial Properties of Doped TiO2 Nanopowders Synthesized by Sol−Gel Method

For environmental applications, nanosized TiO2-based materials are known as the most important photocatalyst and are intensively studied for their advantages such as their higher activity, lower price, and chemical and photoresist properties. Zn or Cu doped TiO2 nanoparticles with anatase crystalline structure were synthesized by sol−gel process. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent, and a hydrolysing agent (ammonia-containing water) was added to obtain a solution with pH 10. The gels were characterized by TG/DTA analysis, SEM, and XPS. Based on TG/DTA results, the temperature of 500 °C was chosen for processing the powders in air. The structure of the samples thermally treated at 500 °C was analysed by XRD and the patterns show crystallization in a single phase of TiO2 (anatase). The surface of the samples and the oxidation states was investigated by XPS, confirming the presence of Ti, O, Zn and Cu. The antibacterial activity of the nanoparticle powder samples was verified using the gram−positive bacterium Staphylococcus aureus. The photocatalytic efficiency of the doped TiO2 nanopowders for degradation of methyl orange (MO) is here examined in order to evaluate the potential applications of these materials for environmental remediation.

Antifungal Effect of Nanoparticles against COVID-19 Linked Black Fungus: A Perspective on Biomedical Applications

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly transmissible and pathogenic coronavirus that has caused a 'coronavirus disease 2019' (COVID-19) pandemic in multiple waves, which threatens human health and public safety. During this pandemic, some patients with COVID-19 acquired secondary infections, such as mucormycosis, also known as black fungus disease. Mucormycosis is a serious, acute, and deadly fungal infection caused by Mucorales-related fungal species, and it spreads rapidly. Hence, prompt diagnosis and treatment are necessary to avoid high mortality and morbidity rates. Major risk factors for this disease include uncontrolled diabetes mellitus and immunosuppression that can also facilitate increases in mucormycosis infections. The extensive use of steroids to prevent the worsening of COVID-19 can lead to black fungus infection. Generally, antifungal agents dedicated to medical applications must be biocompatible, non-toxic, easily soluble, efficient, and hypoallergenic. They should also provide long-term protection against fungal growth. COVID-19-related black fungus infection causes a severe increase in fatalities. Therefore, there is a strong need for the development of novel and efficient antimicrobial agents. Recently, nanoparticle-containing products available in the market have been used as antimicrobial agents to prevent bacterial growth, but little is known about their efficacy with respect to preventing fungal growth, especially black fungus. The present review focuses on the effect of various types of metal nanoparticles, specifically those containing silver, zinc oxide, gold, copper, titanium, magnetic, iron, and carbon, on the growth of various types of fungi. We particularly focused on how these nanoparticles can impact the growth of black fungus. We also discussed black fungus co-infection in the context of the global COVID-19 outbreak, and management and guidelines to help control COVID-19-associated black fungus infection. Finally, this review aimed to elucidate the relationship between COVID-19 and mucormycosis.

Gold Nanoparticle-Based Resuscitation of Cefoxitin against Clinical Pathogens: A Nano-Antibiotic Strategy to Overcome Resistance

Gold nanoparticles have gained popularity as an effective drug delivery vehicle due to their unique features. In fact, antibiotics transported via gold nanoparticles have significantly enhanced their potency in the recent past. The present study used an approach to synthesize gold nanoparticles in one step with the help of cefoxitin antibiotic as a reducing and stabilizing agent. Cefoxitin is a second-generation cephalosporin that loses its potential due to modification in the porins (ompK35 and ompK36) of Gram-negative pathogens. Thus, the present study has developed an idea to revive the potential of cefoxitin against clinical Gram-negative pathogens, i.e., Escherichia coli and Klebsiella pneumoniae, via applying gold nanoparticles as a delivery tool. Prior to antibacterial activity, characterization of cefoxitin-gold nanoparticles was performed via UV-visible spectrophotometry, dynamic light scattering, and electron microscopy. A characteristic UV-visible scan peak for gold nanoparticles was observed at 518 nm, ζ potential was estimated as -23.6 ± 1.6, and TEM estimated the size in the range of 2-12 nm. Moreover, cefoxitin loading efficiency on gold nanoparticles was calculated to be 71.92%. The antibacterial assay revealed that cefoxitin, after loading onto the gold nanoparticles, become potent against cefoxitin-resistant E. coli and K. pneumoniae, and their MIC₅₀ values were estimated as 1.5 μg/mL and 2.5 μg/mL, respectively. Here, gold nanoparticles effectively deliver cefoxitin to the resistant pathogens, and convert it from unresponsive to a potent antibiotic. However, to obtain some convincing conclusions on the human relevance, their fate and toxicity need to be evaluated.

Biopolymeric Ni3S4/Ag2S/TiO2/Calcium Alginate Aerogel for the Decontamination of Pharmaceutical Drug and Microbial Pollutants from Wastewater

The ubiquitous presence of pharmaceutical drugs and microbes in the water is leading to the development of drug resistant microbes. Therefore, efficient materials that can remove or inactivate the drug and microbe contaminants are required. In this work, nickel sulfide/calcium alginate (Ni3S4/CA), silver sulfide/calcium alginate (Ag2S/CA), modified titanium dioxide/calcium alginate (TiO2/CA), and Ni3S4/Ag2S/TiO2/calcium alginate (Ni3S4/Ag2S/TiO2/CA) aerogels have been synthesized for the removal of the oxytetracycline (OTC) drug and microbial contaminants from real beverage industry wastewater. The results revealed that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient for OTC adsorption and inactivation of microbes compared to Ni3S4/CA, Ag2S/CA and TiO2/CA aerogels. The OTC adsorption depends greatly on the solution pH, and optimum OTC removal was observed at pH 6 in its zwitterionic (OTC±) form. The formation of H-bonding and n-π electron donor-acceptors is possible to a considerable extent due to the presence of the double bond benzene ring, oxygen and nitrogen, sulfur-containing functional groups on the OTC molecules, and the Ni3S4/Ag2S/TiO2/CA aerogel. Based on the statistical analysis, root-mean-square deviation (RMSD), chi square (χ2) values, and higher correlation coefficient (R2) values, the Redlich−Peterson isotherm model and Elovich kinetic model are most suited to modelling the OTC adsorption onto Ni3S4/Ag2S/TiO2/CA. The prepared aerogels’ excellent antimicrobial activity is observed in the dark and with solar light irradiation. The zone of inhibition analysis revealed that the antimicrobial activity of the aerogels is in the following order: Ni3S4/Ag2S/TiO2/CA > TiO2/CA > Ag2S/CA > Ni3S4/CA, respectively. Moreover, the antimicrobial results demonstrated that reactive oxygen species, electrons, and active radical species are responsible for growth inhibition and killing of the microbes. These results indicated that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient in decontaminating pollutants from wastewater.

Green Synthesis of Silver Nanoparticles Using Bellevalia Flexuosa Leaves Extract

Silver nanoparticles (AgNPs) have broad biocidal activities, and are widely employed as an active ingredient in antiseptic, anti-viral, and anti-inflammatory preparations. Green-synthesizing AgNPs would be a rapid, cheap, and environmentally friendly method of synthesis. The methanolic extract of the leaves of Bellevalia flexuosa Boiss. (Asparagaceae) was used for the green synthesis of the AgNPs. The effects of the pH and the concentration of silver nitrate (AgNO3) on the synthesis of the AgNPs were investigated. The AgNPs produced above pH 10, and 1 mM of AgNO3 resulted in lower hydrodynamic diameters. Ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction proved the formation of the AgNPs, with a face-centered, cubed geometry. Scanning electron microscopy images showed colloidal and well-dispersed nanoparticles. In addition, the antibacterial activities of the prepared AgNPs were assessed by optical densities (ODs) against Gram-positive bacteria (Enterococcus faecalis and Staphylococcus epidermidis) and Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Salmonella enterica). The broths of Gram-negative and Gram-positive bacteria that contained AgNPs, showed lower OD values compared to the controls. In conclusion, AgNPs were prepared using B. flexuosa methanolic extract, and showed antibacterial activity against the tested bacterial strains.

Emerging starch composite nanofibrous films for food packaging: Facile construction, hydrophobic property, and antibacterial activity enhancement

Polymers synthesized from green resources have many advantages in food packaging and hence their development is very important. Herein, starch/polyvinyl alcohol (PVA) nanofibrous composite films were fabricated by electrospinning technology. Steam-induced cross-linking reaction with glutaraldehyde (GTA) and silver sodium zirconium phosphate (Ag-ZrP) was employed to improve the hydrophobic and antibacterial properties of the constructed nanofibrous films, respectively. The effects of starch/PVA ratio on the micro-morphology and mechanical properties of the binary composite film were investigated. The composite film showed optimal uniformity, bead-free electrospun nanofibers, with enhanced mechanical strength for the 60/40 (v/v) starch/PVA composite. Moreover, the crystallinity of PVA was reduced during the electrospinning process, whereas the introduction of PVA strengthened the hydrogen interactions and improved the thermal stability of the composite films. After the cross-linking with GTA, the starch/PVA films became more hydrophobic. Furthermore, the starch/PVA films embedded with Ag-ZrP had outstanding antibacterial property against both Gram-negative and Gram-positive bacteria. This work demonstrated the potential prospects of electrospun starch nanofibrous films in the food packaging field.

Knowledgebase of potential multifaceted solutions to antimicrobial resistance

Antimicrobial resistance (AMR), a top threat to global health, challenges preventive and treatment strategies of infections. AMR strains of microbial pathogens arise through multiple mechanisms. The underlying "antibiotic resistance genes" (ARGs) spread through various species by lateral gene transfer thereby causing global dissemination. Human methods also augment this process through inappropriate use, non-compliance to treatment schedule, and environmental waste. Worldwide significant efforts are being invested to discover novel therapeutic solutions for tackling resistant pathogens. Diverse therapeutic strategies have evolved over recent years. In this work we have developed a comprehensive knowledgebase by collecting alternative antimicrobial therapeutic strategies from literature data. Therapeutic strategies against bacteria, virus, fungus and parasites were extracted from PubMed literature using text mining. We have used a subjective (sentimental) approach for data mining new strategies, resulting in broad coverage of novel entities and subsequently add objective data like entity name (including IUPAC), potency, and safety information. The extracted data was organized in a freely accessible web platform, KOMBAT. The KOMBAT comprises 1104 Chemical compounds, 220 of newly identified antimicrobial peptides, 42 bacteriophages, 242 phytochemicals, 106 nanocomposites, and 94 novel entities for phototherapy. Entities tested and evaluated on AMR pathogens are included. We envision that this database will be useful for developing future therapeutics against AMR pathogens. The database can be accessed through http://kombat.igib.res.in/.

Photocatalytic Activity Induced by Metal Nanoparticles Synthesized by Sustainable Approaches: A Comprehensive Review

Nanotechnology is a fast-expanding area with a wide range of applications in science, engineering, health, pharmacy, and other fields. Among many techniques that are employed toward the production of nanoparticles, synthesis using green technologies is the simplest and environment friendly. Nanoparticles produced from plant extracts have become a very popular subject of study in recent decades due to their diverse advantages such as low-cost synthesis, product stability, and ecofriendly protocols. These merits have prompted the development of nanoparticles from a variety of sources, including bacteria, fungi, algae, proteins, enzymes, etc., allowing for large-scale production with minimal contamination. However, nanoparticles obtained from plant extracts and phytochemicals exhibit greater reduction and stabilization and hence have proven the diversity of properties, like catalyst/photocatalyst, magnetic, antibacterial, cytotoxicity, circulating tumor deoxy ribo nucleic acid (CT-DNA) binding, gas sensing, etc. In the current scenario, nanoparticles can also play a critical role in cleaning wastewater and making it viable for a variety of operations. Nano-sized photocatalysts have a great scope toward the removal of large pollutants like organic dyes, heavy metals, and pesticides in an eco-friendly and sustainable manner from industrial effluents. Thus, in this review article, we discuss the synthesis of several metal nanoparticles using diverse plant extracts, as well as their characterization via techniques like UV–vis (ultraviolet–visible), XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FTIR (Fourier transform infrared spectroscopy), etc., and catalytic activity on various hazardous systems.

Antibacterial and antibiofilm effects of silver nanoparticles against the uropathogen Escherichia coli U12

The drug-resistant bacterial strains' emergence increases day by day. This may be a result of biofilm presence, which protects bacteria from antimicrobial agents. Thus, new approaches must be used to control biofilm-related infections in healthcare settings. In such a study, biological silver nanoparticles were introduced in such a study as an anti-biofilm agent against multidrug-resistant E. coli U12 on urinary catheters. Seven different silver nanoparticles concentrations were tested for their antimicrobial activities. Also, anti-biofilm activities against E. coli U12 were tested. Using the dilution method, the silver nanoparticles concentration of 85 μg/ml was the MIC (Minimum Inhibitory Concentration) that had excellent biocompatibility and showed significant antibacterial activity against E. coli U12. Scanning electron microscopy (SEM) confirmed that the highest efficient dose of silver nanoparticles was 340 μg/ml at 144 h that reduced adhesion of E. coli U12 to the urinary catheter. E. coli U12 cells ruptured cell walls and cell membranes after being examined using transmission electron microscopy (TEM). Thus, biologically prepared silver nanoparticles could be used to coat medical devices since it is effective and promising to inhibit biofilm formation by impregnating urinary catheters with silver nanoparticles.

Zinc Oxide Nanoparticles (ZnO NPs) and N-Methylol Dimethyl Phosphonopropion Amide (MDPA) System for Flame Retardant Cotton Fabrics

The aim of the present research work was to develop halogen and formaldehyde-free, durable flame retardant fabric along with multifunctional properties and to find the optimal conditions and parameters. In this research, zinc oxide nanoparticles (ZnO NPs) were grown onto 100% cotton fabric using the sonochemical method. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and sodium hydroxide (NaOH) were used as precursors. After ZnO NPs growth, N-Methylol dimethylphosphonopropionamide (MDPA) flame retardant was applied in the presence of 1, 2, 3, 4-butanetetracarboxylic acid (BTCA) as cross-linkers using the conventional pad-dry-cure method. Induced coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine the deposited amount of Zn and phosphorous (P) contents. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) were employed to determine the surface morphology and characterization of the developed samples. Furthermore, the thermal degradation of the untreated and treated samples was investigated by thermogravimetric analysis (TGA). Furthermore, the vertical flame retardant test, limiting oxygen index (LOI), ultraviolet protection factor (UPF), and antibacterial activity of samples were examined. The developed samples showed excellent results for flame retardancy (i.e., 39 mm char length, 0 s after flame time, 0 s after glow time), 32.2 LOI, 143.76 UPF, and 100% antibacterial activity.

Innovative Insights into In Vitro Activity of Colloidal Platinum Nanoparticles against ESBL-Producing Strains of Escherichia coli and Klebsiella pneumoniae

Growing morbidity and mortality rates due to increase in the number of infections caused by MDR (multi-drug resistant) microorganisms are becoming some of the foremost global health issues. Thus, the need to search for and find novel approaches to fight AMR (antimicrobial resistance) has become obligatory. This study aimed to determine the antimicrobial properties of commercially purchased colloidal platinum nanoparticles by examining the existence and potency of their antibacterial effects and investigating the mechanisms by means of which they express these activities. Antimicrobial properties were investigated with respect to standard laboratory ATCC (American Type Cell Culture) and clinical extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia (E.) coli and Klebsiella (K.) pneumoniae. Standard microbiological methods of serial microdilution, modulation of microbial cell death kinetics (“time–kill” assays), and biofilm inhibition were used. Bacterial cell wall damage and ROS (reactive oxygen species) levels were assessed in order to explore the mechanisms of platinum nanoparticles’ antibacterial activities. Platinum nanoparticles showed strong antibacterial effects against all tested bacterial strains, though their antibacterial effects were found to succumb to time kinetics. Antibiofilm activity was modest overall and significantly effective only against E. coli strains. By measuring extracellular DNA/RNA and protein concentrations, induced bacterial cell wall damage could be assumed. The determination of ROS levels induced by platinum nanoparticles revealed their possible implication in antibacterial activity. We conclude that platinum nanoparticles exhibit potent antibacterial effects against standard laboratory and resistant strains of E. coli and K. pneumoniae. Both, cell wall damage and ROS induction could have important role as mechanisms of antibacterial activity, and, require further investigation.

Synthesis and Characterization of Boehmite Particles Obtained from Recycling: Water Disinfection Application

We report on the synthesis of boehmite aluminum oxide hydroxide particles with lamellar structure (γ-AlO(OH)) obtained from the recycling of metallic can seals, with the addition of silver nanoparticles (Ag-NPs) reduced by Aloe Vera extract. X-ray diffractometry (XRD) confirmed the γ-phase, and scanning electron microscopy (SEM) showed the presence of Ag-NPs on the boehmite particle surface, confirming the efficiency of the synthesis to obtain the composite material. The samples were used to treat lake water, according to the Standard Methods for the Examination of Water and Wastewater. The results indicated that the elimination of total coliforms and Escherichia coli occurred, with excellent efficiency for the Ag-boehmite sample. The tests show the possibility of reuse (5×) of the sample, as it maintained the efficiency of disinfection for E. coli. The preparation, use, and reuse of boehmite obtained from metallic waste is a case of a circular economy, focused on sustainability and green chemistry.

Innovative Treatment Strategies to Accelerate Wound Healing: Trajectory and Recent Advancements

Wound healing is highly specialized dynamic multiple phase process for the repair of damaged/injured tissues through an intricate mechanism. Any failure in the normal wound healing process results in abnormal scar formation, and chronic state which is more susceptible to infections. Chronic wounds affect patients’ quality of life along with increased morbidity and mortality and are huge financial burden to healthcare systems worldwide, and thus requires specialized biomedical intensive treatment for its management. The clinical assessment and management of chronic wounds remains challenging despite the development of various therapeutic regimens owing to its painstakingly long-term treatment requirement and complex wound healing mechanism. Various conventional approaches such as cell therapy, gene therapy, growth factor delivery, wound dressings, and skin grafts etc., are being utilized for promoting wound healing in different types of wounds. However, all these abovementioned therapies are not satisfactory for all wound types, therefore, there is an urgent demand for the development of competitive therapies. Therefore, there is a pertinent requirement to develop newer and innovative treatment modalities for multipart therapeutic regimens for chronic wounds. Recent developments in advanced wound care technology includes nanotherapeutics, stem cells therapy, bioengineered skin grafts, and 3D bioprinting-based strategies for improving therapeutic outcomes with a focus on skin regeneration with minimal side effects. The main objective of this review is to provide an updated overview of progress in therapeutic options in chronic wounds healing and management over the years using next generation innovative approaches. Herein, we have discussed the skin function and anatomy, wounds and wound healing processes, followed by conventional treatment modalities for wound healing and skin regeneration. Furthermore, various emerging and innovative strategies for promoting quality wound healing such as nanotherapeutics, stem cells therapy, 3D bioprinted skin, extracellular matrix-based approaches, platelet-rich plasma-based approaches, and cold plasma treatment therapy have been discussed with their benefits and shortcomings. Finally, challenges of these innovative strategies are reviewed with a note on future prospects.

Catalytic potential of endophytes facilitates synthesis of biometallic zinc oxide nanoparticles for agricultural application

Recent advances fascinated the use of biological resources in combination with metals to obtain high quality biometals and apply its advantages in different fields. Endophytic mediated Zinc oxide nanoparticles (ZnO-NPs) is an economical and ecofriendly way for farmers to avoid Zn deficiency in rice crop and obtain high yield. Here we synthesized ZnO-NPs utilizing endophytic bacterial strain of Enterobacter hormaechei (E. hormaechei). The physiochemical properties of the prepared NPs were determined through UV-Vis spectroscopy, XRD, FT-IR, SEM and TEM. The prepared NPs revealed surface plasmon resonance (SPR) at 320 nm (nm) and crystalline structure with 21 nm average crystalline size. FT-IR spectra showed the presence of carboxylic, alcohol and amine functional groups, which confirm the biometallic assembling of the ZnO and endophytic bacterial functional groups. SEM showed pyramidal symmetry whereas TEM revealed poly dispersed spherical shape with particle size distribution 18-48 nm. Our results showed that prepared NPs possess significant antifungal, antibacterial and antioxidant potential at 25, 50 and 100 µg/mL concentrations. Moreover, Cytotoxic and hemolytic assay showed significant results (less % viability and hemolysis activity) at 50 and 100 µg/mL (ZnO-NP's) concentrations as compared to control. The prepared ZnO-NPs were used as bio fertilizer in various concentrations as a foliar spray, which showed significant enhancement of the rice plant growth, along with chlorophyll, proteins and carotenoid contents. These results recommend that endophytic mediated ZnO-NPs are biocompatible and possess significant potential for agricultural applications.

Remedial Aspect of Zinc Oxide Nanoparticles Against Serratia Marcescens and Enterococcus Faecalis

Zinc oxide nanoparticles (ZnO NPs) have been widely used in biomedical applications due to their high biocompatibility and low toxicity to humans. The present work aimed to investigate the antibacterial effects of different concentrations of ZnO NPs on two opportunistic pathogens, Serratia marcescens and Enterococcus faecalis. The surface interaction between nanoparticles and bacterial cell wall, and the subsequent morphological alterations on the bacterial surface, were examined through Fourier transform infrared spectroscopy and scanning electron microscope. The energy dispersive X-ray analysis was used to confirm the elemental composition of ZnO NPs and the cellular accumulation of ZnO NPs in bacteria. The growth-inhibitory test demonstrated a dose-dependent growth inhibitory effect of ZnO NPs against both the test bacteria, as the higher concentration of nanoparticles caused the higher bacterial growth inhibition. The results showed that ZnO NPs caused a higher growth inhibition (63.50 ± 2.50%) on the Gram-positive bacterium E. faecalis compared to the Gram-negative bacterium S. marcescens (51.27 ± 4.56%). Fourier transform infrared spectrum revealed the possible involvement of hydroxyl, carboxyl, amides, methylene, and phosphate groups from the biomolecules of bacterial cell wall such as proteins, carbohydrates, lipids, and phospholipids in the interaction of ZnO NPs on bacterial cell surface. Energy dispersive X-ray analysis showed the higher accumulation of ZnO NPs in E. faecalis than S. marcescens analogous to the bacterial growth inhibition. Scanning electron microscopy images confirmed the antibacterial properties of ZnO NPs, showing the loss of integrity of cell membrane and distortion of bacterial cells. Hence, the potential of ZnO NP as an antibacterial agent against S. marcescens and E. faecalis has been confirmed.

Synergism between metallic nanoparticles and antibiotics

The discovery of antibiotics in the twentieth century made it possible to treat bacterial infections and revolutionized modern medicine. However, gradually, it is possible to perceive a decrease in the effectiveness of antimicrobial agents against pathogenic isolates, which, together with the low investment in the discovery and/or development of new antibiotics by large pharmaceutical companies since the 1960s, makes it increasingly difficult to treatment of infections caused by these microorganisms. The search for strategies capable of potentiating the effect of existing drugs through the development of new therapeutic approaches, which also have the potential to circumvent bacterial resistance to antibiotics, has become indispensable. In this context, metallic nanoparticles stand out, as they could be used to act synergistically with drugs. Thus, the objective of this review was to present the latest information on the synergistic activity of antibiotics with metallic nanoparticles, pointing out this association as a promising alternative for the preservation of bacterial sensitivity to these drugs. The different metallic nanoparticles can present different benefits in the treatment of bacterial infections, with this being able to potentiate the bacterial activity of antibiotics that are widely used in the clinic, being able to increase the susceptibility in multiresistant microorganisms. KEY POINTS: • Metallic nanoparticles increased the antimicrobial action of drugs; • Metallic nanoparticles compromise the action of bacterial efflux pumps; • Biofilm formation was inhibited after treatment with metallic nanoparticles.

Removal of Contaminants from Water by Membrane Filtration: A Review

Drinking water sources are increasingly subject to various types of contamination due to anthropogenic factors and require proper treatment to remove disease-causing agents. Public drinking water systems use different treatment methods to provide safe and quality drinking water to populations. However, they are ineffective in removing contaminants that are considered a danger to the environment and therefore to humans. Several alternative treatment processes have been proposed, such as membrane filtration, as final purification methods. This paper aims to summarize the type of pollutant compounds, filtration processes, and membranes that have been most studied in this area with particular emphasis on how the modification of membranes, either the manufacturing process or the incorporation of nanomaterials, influences their performance.

A Critical Review of the Antimicrobial and Antibiofilm Activities of Green-Synthesized Plant-Based Metallic Nanoparticles

Metallic nanoparticles (MNPs) produced by green synthesis using plant extracts have attracted huge interest in the scientific community due to their excellent antibacterial, antifungal and antibiofilm activities. To evaluate these pharmacological properties, several methods or protocols have been successfully developed and implemented. Although these protocols were mostly inspired by the guidelines from national and international regulatory bodies, they suffer from a glaring absence of standardization of the experimental conditions. This situation leads to a lack of reproducibility and comparability of data from different study settings. To minimize these problems, guidelines for the antimicrobial and antibiofilm evaluation of MNPs should be developed by specialists in the field. Being aware of the immensity of the workload and the efforts required to achieve this, we set out to undertake a meticulous literature review of different experimental protocols and laboratory conditions used for the antimicrobial and antibiofilm evaluation of MNPs that could be used as a basis for future guidelines. This review also brings together all the discrepancies resulting from the different experimental designs and emphasizes their impact on the biological activities as well as their interpretation. Finally, the paper proposes a general overview that requires extensive experimental investigations to set the stage for the future development of effective antimicrobial MNPs using green synthesis.

Self-redox reaction driven in situ formation of Cu2O/Ti3C2Tx nanosheets boost the photocatalytic eradication of multi-drug resistant bacteria from infected wound

BACKGROUND

MXenes with interesting optical and electrical properties have been attractive in biomedical applications such as antibacterial and anticancer agents, but their low photogeneration efficiency of reactive oxygen species (ROS) and poor stability are major concerns against microbial resistance.

METHODS

Water-dispersible single layer Ti₃C₂T_x-based MXene through etching tightly stacked MAX phase precursor using a minimally intensive layer delamination method. After addition of Cu(II) ions, the adsorbed Cu(II) ions underwent self-redox reactions with the surface oxygenated moieties of MXene, leading to in situ formation of Cu₂O species to yield Cu₂O/Ti₃C₂T_x nanosheets (heterostructures).

RESULTS

Under NIR irradiation, the Cu₂O enhanced generation of electron-hole pairs, which boosted the photocatalytic production of superoxide and subsequent transformation into hydrogen peroxide. Broad-spectrum antimicrobial performance of Cu₂O/Ti₃C₂T_x nanosheets with sharp edges is attributed to the direct contact-induced membrane disruption, localized photothermal therapy, and in situ generated cytotoxic free radicals. The minimum inhibitory concentration of Cu₂O/Ti₃C₂T_x nanosheets reduced at least tenfold upon NIR laser irradiation compared to pristine Cu₂O/Ti₃C₂T_x nanosheets. The Cu₂O/Ti₃C₂T_x nanosheets were topically administrated on the methicillin-resistant Staphylococcus aureus (MRSA) infected wounds on diabetic mice.

CONCLUSION

Upon NIR illumination, Cu₂O/Ti₃C₂T_x nanosheets eradicated MRSA and their associated biofilm to promote wound healing. The Cu₂O/Ti₃C₂T_x nanosheets with superior catalytic and photothermal properties have a great scope as an effective antimicrobial modality for the treatment of infected wounds.

Antibiotic resistant bacteria: current situation and treatment options to accelerate the development of a new antimicrobial arsenal

INTRODUCTION

Antibiotic resistance is one of the biggest public health threats worldwide. Currently, antibiotic-resistant bacteria kill 700,000 people every year. These data represent the near future in which we find ourselves, a "post-antibiotic era" where the identification and development of new treatments are key. This review is focused on the current and emerging antimicrobial therapies which can solve this global threat.

AREAS COVERED

Through a literature search using databases such as Medline and Web of Science, and search engines such as Google Scholar, different antimicrobial therapies were analyzed, including pathogen-oriented therapy, phagotherapy, microbiota and antivirulent therapy. Additionally, the development pathways of new antibiotics were described, emphasizing on the potential advantages that the combination of a drug repurposing strategy with the application of mathematical prediction models could bring to solve the problem of AMRs.

EXPERT OPINION

This review offers several starting points to solve a single problem: reducing the number of AMR. The data suggest that the strategies described could provide many benefits to improve antimicrobial treatments. However, the development of new antimicrobials remains necessary. Drug repurposing, with the application of mathematical prediction models, is considered to be of interest due to its rapid and effective potential to increase the current therapeutic arsenal.

Electrospun Membrane Surface Modification by Sonocoating with HA and ZnO:Ag Nanoparticles—Characterization and Evaluation of Osteoblasts and Bacterial Cell Behavior In Vitro

Guided tissue regeneration and guided bone regeneration membranes are some of the most common products used for bone regeneration in periodontal dentistry. The main disadvantage of commercially available membranes is their lack of bone cell stimulation and easy bacterial colonization. The aim of this work was to design and fabricate a new membrane construct composed of electrospun poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) fibers sonocoated with layers of nanoparticles with specific properties, i.e., hydroxyapatite and bimetallic nanocomposite of zinc oxide–silver. Thus, within this study, four different variants of biomaterials were evaluated, namely: poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) biomaterial, poly(D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite biomaterial, poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano zinc oxide–silver biomaterial, and poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver biomaterial. First, it was demonstrated that the wettability of biomaterials—a prerequisite property important for ensuring desired biological response—was highly increased after the sonocoating process. Moreover, it was indicated that biomaterials composed of poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) with or without a nano hydroxyapatite layer allowed proper osteoblast growth and proliferation, but did not have antibacterial properties. Addition of a nano zinc oxide–silver layer to the biomaterial inhibited growth of bacterial cells around the membrane, but at the same time induced very high cytotoxicity towards osteoblasts. Most importantly, enrichment of this biomaterial with a supplementary underlayer of nano hydroxyapatite allowed for the preservation of antibacterial properties and also a decrease in the cytotoxicity towards bone cells, associated with the presence of a nano zinc oxide–silver layer. Thus, the final structure of the composite poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver seems to be a promising construct for tissue engineering products, especially guided tissue regeneration/guided bone regeneration membranes. Nevertheless, additional research is needed in order to improve the developed construct, which will simultaneously protect the biomaterial from bacterial colonization and enhance the bone regeneration properties.

Experimental Confirmation of Antimicrobial Effects of GdYVO4:Eu3+ Nanoparticles

Nanotechnology can be applied to design antibacterial agents to combat antibiotic resistance. The aim of the present study was to assess the antimicrobial effects and cytotoxicity of GdYVO₄:Eu³⁺ nanoparticles (NPs). Biofilm inhibition activity, antimicrobial activity, bacterial viability inhibition and DNA cleavage activity of GdYVO₄:Eu³⁺ NPs were studied. In addition, the impact of GdYVO₄:Eu³⁺ NPs on the mitochondrial membrane potential (ΔΨ_M) of host immune cells and, hence, their apoptosis was analyzed by JC-1 staining using flow cytometry. GdYVO₄:Eu³⁺ NPs demonstrated good antimicrobial, cell viability inhibition and DNA cleavage activities. In addition, GdYVO₄:Eu³⁺ NPs showed good biofilm inhibition activity against S. aureus and P. aeruginosa and inhibition percentages were 89.15% and 79.54%, respectively. However, GdYVO₄:Eu³⁺ NPs promoted mitochondrial depolarization and apoptosis of leukocytes at high concentrations. GdYVO₄:Eu³⁺ nanoparticles are promising antibacterial agents. However, more efforts should be exerted to ensure their safety.

Antibacterial Activity of Silver and Gold Particles Formed on Titania Thin Films

Metal-based nanoparticles with antimicrobial activity are gaining a lot of attention in recent years due to the increased antibiotics resistance. The development and the pathogenesis of oral diseases are usually associated with the formation of bacteria biofilms on the surfaces; therefore, it is crucial to investigate the materials and their properties that would reduce bacterial attachment and biofilm formation. This work provides a systematic investigation of the physical-chemical properties and the antibacterial activity of TiO2 thin films decorated by Ag and Au nanoparticles (NP) against Veillonella parvula and Neisseria sicca species associated with oral diseases. TiO2 thin films were formed using reactive magnetron sputtering by obtaining as-deposited amorphous and crystalline TiO2 thin films after annealing. Au and Ag NP were formed using a two-step process: magnetron sputtering of thin metal films and solid-state dewetting. The surface properties and crystallographic nature of TiO2/NP structures were investigated by SEM, XPS, XRD, and optical microscopy. It was found that the higher thickness of Au and Ag thin films results in the formation of the enlarged NPs and increased distance between them, influencing the antibacterial activity of the formed structures. TiO2 surface with AgNP exhibited higher antibacterial efficiency than Au nanostructured titania surfaces and effectively reduced the concentration of the bacteria. The process of the observation and identification of the presence of bacteria using the deep learning technique was realized.

Antimicrobial Activity Enhancers: Towards Smart Delivery of Antimicrobial Agents

The development of effective treatments against infectious diseases is an extensive and ongoing process due to the rapid adaptation of bacteria to antibiotic-based therapies. However, appropriately designed activity enhancers, including antibiotic delivery systems, can increase the effectiveness of current antibiotics, overcoming antimicrobial resistance and decreasing the chance of contributing to further bacterial resistance. The activity/delivery enhancers improve drug absorption, allow targeted antibiotic delivery, improve their tissue and biofilm penetration and reduce side effects. This review provides insights into various antibiotic activity enhancers, including polymer, lipid, and silver-based systems, designed to reduce the adverse effects of antibiotics and improve formulation stability and efficacy against multidrug-resistant bacteria.

Overcoming Multidrug Resistance of Antibiotics via Nanodelivery Systems

Antibiotic resistance has become a threat to microbial therapies nowadays. The conventional approaches possess several limitations to combat microbial infections. Therefore, to overcome such complications, novel drug delivery systems have gained pharmaceutical scientists’ interest. Significant findings have validated the effectiveness of novel drug delivery systems such as polymeric nanoparticles, liposomes, metallic nanoparticles, dendrimers, and lipid-based nanoparticles against severe microbial infections and combating antimicrobial resistance. This review article comprises the specific mechanism of antibiotic resistance development in bacteria. In addition, the manuscript incorporated the advanced nanotechnological approaches with their mechanisms, including interaction with the bacterial cell wall, inhibition of biofilm formations, activation of innate and adaptive host immune response, generation of reactive oxygen species, and induction of intracellular effect to fight against antibiotic resistance. A section of this article demonstrated the findings related to the development of delivery systems. Lastly, the role of microfluidics in fighting antimicrobial resistance has been discussed. Overall, this review article is an amalgamation of various strategies to study the role of novel approaches and their mechanism to fight against the resistance developed to the antimicrobial therapies.

The role of nanoparticles (titanium dioxide, graphene oxide) on the inactivation of co-existing bacteria in the presence and absence of quartz sand

The increased mass production and application of engineered nanomaterials (ENMs) have resulted in the release of nanoparticles (NPs) in the environment, raising uncertainties regarding their environmental impacts. This study examines the effect of graphene oxide (GO) and titanium dioxide (TiO₂) NPs on the inactivation of the three model bacteria originated by mammalians including humans: Escherichia (E.) coli, Enterococcus (E.) faecalis, and Staphylococcus (S.) aureus. A series of dynamic batch experiments were conducted at constant room temperature (22 °C) in order to examine the inactivation of co-existing bacteria by NPs, in the presence and absence of quartz sand. The inactivation experimental data were satisfactorily fitted with a pseudo-first order expression with a time dependent rate coefficient. The inactivation of E. coli and S. aureus was shown to increase in the co-presence of GO or TiO₂ NPs and quartz sand comparing with the presence of GO or TiO₂ NPs alone. For E. faecalis, no clear trend was observed. Moreover, quartz sand was shown to affect inactivation of bacteria by GO and TiO₂ NPs. Among the bacteria examined, the highest inactivation rates were observed for S. aureus.

Endophytic Microorganisms From the Tropics as Biofactories for the Synthesis of Metal-Based Nanoparticles: Healthcare Applications

Nanoparticles (NPs) have gained great attention in recent years due to their extensive and innovative applications in the field of medicine. However, conventional physicochemical approaches for the synthesis of NPs may be limited and costly, and the reaction by-products are potentially toxic for human health and the environment. Bio-mediated synthesis of NPs exploiting microorganisms as nanofactories has emerged as an alternative to traditional methods, as it provides economic and environmental benefits. Tropical ecosystems harbor a high diversity of endophytes, which have a diverse array of metabolic pathways that confer habitat adaptation and survival and that can be used to produce novel bioactive compounds with a variety of biological properties. Endophytic bacteria and fungi cultivated under optimum conditions have potential for use in biogenic synthesis of NPs with different characteristics and desired activities for medical applications, such as antimicrobial, antitumoral, antioxidant and anti-inflammatory properties. The bio-mediated synthesis of metal-based NPs can be favored because endophytic microorganisms may tolerate and/or adsorb metals and produce enzymes used as reducing agents. To our knowledge, this is the first review that brings together exclusively current research highlighting on the potential of endophytic bacteria and fungi isolated from native plants or adapted to tropical ecosystems and tropical macroalgae as nanofactories for the synthesis of NPs of silver, gold, copper, iron, zinc and other most studied metals, in addition to showing their potential use in human health.

Effect of Silver Nanoparticles (AgNPs) on Candida Albicans, Candida Dubliniensis, and Candida Guilliermondii

Background:

Candida species are the most important fungal pathogens and are sometimes considered the fourth most common cause of infection in hospitals. Today, research needs to be conducted on the antifungal effect of silver nanoparticles (AgNPs) due to toxicity, side effects, and drug interactions of antifungal chemical drugs.

Objective:

Therefore, this study was done to evaluate the antifungal activity of AgNPs on Candida albicans, Candida dubliniensis, and Candida guilliermondii.

Methodology:

Antifungal activity of AgNPs on Candida albicans, Candida dubliniensis, and Candida guilliermondii was assessed by agar and macrodilution diffusion methods in an in-vitro investigation. Structural changes were investigated by scanning electron microscope (SEM). Then, the obtained data were evaluated by SPSS statistical software.

Results:

Based on the results, the mean diameter of growth inhibition halos by AgNPs was equal to 20, 20.2, and 40.7mm for Candida albicans, Candida dubliniensis, and Candida guilliermondii, respectively. The minimum inhibitory concentrations (MIC) equal 62.50, 31.25, and 15.62 mg/ml for Candida albicans, Candida dubliniensis, and Candida guilliermondii, respectively. The minimum fungicidal concentrations (MFC) were equal to 125, 62.50, and 31.25 mg/ml for Candida albicans, Candida dubliniensis, and Candida guilliermondii, respectively.

Conclusion:

Our results revealed that AgNPs inhibit the growth of Candida albicans, Candida dubliniensis, and Candida guilliermondii. SEM observations also showed that NPs disrupted cell membrane/wall. Changes in yeast levels from smooth to uneven were also observed.

Cefotaxime Mediated Synthesis of Gold Nanoparticles: Characterization and Antibacterial Activity

Cefotaxime (CTX) is a third-generation cephalosporin antibiotic with broad-spectrum activity against Gram negative and Gram positive bacteria. However, like other third-generation cephalosporin antibiotics, its efficacy is declining due to the increased prevalence of multidrug-resistant (MDR) pathogens. Recent advances in nanotechnology have been projected as a practical approach to combat MDR microorganisms. Therefore, in the current study, gold nanoparticles (AuNPs) were prepared using cefotaxime sodium, which acted as a reducing and capping agent, besides having well-established antibacterial activity. The synthesized cefotaxime-loaded gold nanoparticles (C-AuNPs) were characterized by UV-Visible spectroscopy, FTIR, TEM and DLS. In addition, the in vitro antibacterial activity of C-AuNPs was assessed against both Gram-positive and Gram-negative bacteria. UV-Visible spectroscopy verified the formation of C-AuNPs, while TEM and DLS verified their nano-size. In addition, CTX loading onto AuNPs was confirmed by FTIR. Furthermore, the colloidal stability of the synthesized C-AuNPs was ascribed to the higher net negative surface charge of C-AuNPs. Most importantly, the synthesized C-AuNPs showed superior antibacterial activity and lower minimum inhibitory concentration (MIC) values against Gram-negative (Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria, compared with pure CTX. Collectively, CTX was successfully adopted, as reducing and capping agent, to synthesize stable, nano-sized spherical C-AuNPs. Furthermore, loading CTX onto AuNPs could efficiently restore and/or boost the antibacterial activity of CTX against resistant Gram-negative and Gram-positive bacteria.

Carbon nanogels exert multipronged attack on resistant bacteria and strongly constrain resistance evolution

Developing antimicrobial agents that can eradicate drug-resistant (DR) bacteria and provide sustained protection from DR bacteria is a major challenge. Herein, we report a mild pyrolysis approach to prepare carbon nanogels (CNGs) through polymerization and the partial carbonization of l-lysine hydrochloride at 270 °C as a potential broad-spectrum antimicrobial agent that can inhibit biopolymer-producing bacteria and clinical drug-resistant isolates and tackle drug resistance issues. We thoroughly studied the structures of the CNGs, their antibacterial mechanism, and biocompatibility. CNGs possess superior bacteriostatic effects against drug-resistant bacteria compared to some commonly explored antibacterial nanomaterials (silver, copper oxide, and zinc oxide nanoparticles, and graphene oxide) through multiple antimicrobial mechanisms, including reactive oxygen species generation, membrane potential dissipation, and membrane function disruption, due to the positive charge and flexible colloidal structures resulting strong interaction with bacterial membrane. The minimum inhibitory concentration (MIC) values of the CNGs (0.6 µg mL^-1 against E. coli and S. aureus) remained almost the same against the bacteria after 20 passages; however, the MIC values increased significantly after treatment with silver nanoparticles, antibiotics, the bacteriostatic chlorhexidine, and especially gentamicin (approximately 140-fold). Additionally, the CNGs showed a negligible MIC value difference against the obtained resistant bacteria after acclimation to the abovementioned antimicrobial agents. The findings of this study unveil the development of antimicrobial CNGs as a sustainable solution to combat multidrug-resistant bacteria.

Current Knowledge on the Oxidative-Stress-Mediated Antimicrobial Properties of Metal-Based Nanoparticles

The emergence of multidrug-resistant (MDR) bacteria in recent years has been alarming and represents a major public health problem. The development of effective antimicrobial agents remains a key challenge. Nanotechnologies have provided opportunities for the use of nanomaterials as components in the development of antibacterial agents. Indeed, metal-based nanoparticles (NPs) show an effective role in targeting and killing bacteria via different mechanisms, such as attraction to the bacterial surface, destabilization of the bacterial cell wall and membrane, and the induction of a toxic mechanism mediated by a burst of oxidative stress (e.g., the production of reactive oxygen species (ROS)). Considering the lack of new antimicrobial drugs with novel mechanisms of action, the induction of oxidative stress represents a valuable and powerful antimicrobial strategy to fight MDR bacteria. Consequently, it is of particular interest to determine and precisely characterize whether NPs are able to induce oxidative stress in such bacteria. This highlights the particular interest that NPs represent for the development of future antibacterial drugs. Therefore, this review aims to provide an update on the latest advances in research focusing on the study and characterization of the induction of oxidative-stress-mediated antimicrobial mechanisms by metal-based NPs.

Metallic Structures: Effective Agents to Fight Pathogenic Microorganisms

The current worldwide pandemic caused by coronavirus disease 2019 (COVID-19) had alerted the population to the risk that small microorganisms can create for humankind’s wellbeing and survival. All of us have been affected, directly or indirectly, by this situation, and scientists all over the world have been trying to find solutions to fight this virus by killing it or by stop/decrease its spread rate. Numerous kinds of microorganisms have been occasionally created panic in world history, and several solutions have been proposed to stop their spread. Among the most studied antimicrobial solutions, are metals (of different kinds and applied in different formats). In this regard, this review aims to present a recent and comprehensive demonstration of the state-of-the-art in the use of metals, as well as their mechanisms, to fight different pathogens, such as viruses, bacteria, and fungi.