Polyethyleneimine Capped Silver Nanoclusters as Efficient Antibacterial Agents

Bioinspired synthesis of multifunctional, highly stable polymeric templated silver-silica colloids as catalytic and antibacterial coatings for paper

In this paper, a simple, bottom up, bioinspired technique is proposed for the synthesis of highly stable colloids of silica supported spherical silver nanoparticles (SiO2@Ag) that act as efficient catalytic and antimicrobial coatings for an organic substrate, filter paper. The core - shell structure and the highly branched dendritic polymer, poly(ethylene)imine, enabled the precise control of growth rate and morphology of silica and silver nanoparticles. The polymer also enabled the deposition of these nanoparticles onto an organic substrate, filter paper, through immersion by modifying its surface. The catalytic and antibacterial properties of these samples were assessed. The results obtained from this analysis showed a complete degradation of an aqueous pollutant, 4-nitrophenol, for 6 successive catalytic cycles without intermediate purification steps. Furthermore, the polymeric silica-silver suspension proved to express antibacterial activity against both Gram-positive and Gram-negative bacteria (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa). The antibacterial properties were evaluated according to the disk diffusion method, whereas the Minimum Inhibitory Concentration was also determined. The samples were examined by Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction analysis, z-potential analysis, Fourier Transform Infrared Spectroscopy and Ultraviolet-visible Spectroscopy.

Antimicrobial and Cytotoxic Effect of Positively Charged Nanosilver-Coated Silk Sutures

Sutures are a crucial component of surgical procedures, serving to close and stabilize wound margins to promote healing. However, microbial contamination of sutures can increase the risk of surgical site infections (SSI) due to colonization by pathogens. This study aimed to tackle SSI by synthesizing positively charged silver nanoparticles (P-AgNPs) and using them to produce antimicrobial sutures. The P-AgNPs were reduced and stabilized using polyethylenimine (PEI), a cationic branched polymer. The physiochemical characteristics of P-AgNPs were confirmed from the surface plasmon resonance (SPR) peak at 419 nm, spherical morphology with a particle size range of 8-10 nm, PEI functional groups on NPs, a hydrodynamic diameter of 12.3 ± 2.4 nm, and a zeta potential of 31.3 ± 6 mV. Subsequently, the surfaces of silk sutures were impregnated with P-AgNPs at different time intervals (24, 48, and 96 h) using an ex situ method. Scanning electron microscopy (SEM) and tensile strength studies were conducted to determine the coating and durability of the NP-coated sutures. The NPs were quantified on sutures using inductively coupled plasma optical emission spectrophotometry (ICP-OES), which was in the range of 1-5 μg. Primarily, antimicrobial activity was studied using three microorganisms (Candida albicans, Streptococcus mutans, and Staphylococcus aureus) for both P-AgNPs and suture-coated P-AgNPs using the agar diffusion method. The results showed that only the NPs and NP-coated sutures exhibited enhanced antimicrobial effects against bacteria and fungi. Finally, the cytotoxicity of the sutures was investigated using stem cells from the apical papilla (SCAPs) for 24 h, which exhibited more than 75% cell viability. Overall, the results indicate that NP-coated sutures can potentially be used as antimicrobial sutures to diminish or inhibit SSI in postoperative or general surgery patients.

Evaluation of AgNCs@PEI and their integrated hydrogel for colorimetric and fluorometric detection of ascorbic acid

A dual-mode colorimetric and fluorometric sensor based on water soluble silver nanoclusters (AgNCs@PEI) is developed for quantitative and visual detection of ascorbic acid (Asc A). The detection method relies on the Asc A induced aggregation of AgNCs@PEI, which resulted in fluorecsence quenching of the sensor. The clusters exhibited a unique combination of static and collisional quenching with a wide range of dynamic detection (1-105 µM) Linear relationship was observed in the concentration range 102-103 µM using fluorescence and 0.2 × 102-5 × 103 μM using absorbance spectroscopy with respective detection limits of 10.65 μM and 2.49 μM. The corresponding colorimetric and fluorometric changes can be easily monitored by the naked eye with a visual detection limit of 103 μM. AgNCs@PEI were further integrated within a hydrogel for developing a solid-state visual detection platform. Notably, the sensing response of the clusters towards Asc A remained unaltered even after hydrogel integration. Additionally, digital image analysis was adopted, which improved the sensitivity of instrument-free fluorescence detection of Asc A. Analysis by the developed sensor showed excellent recovery percentages of Asc A in spiked urine samples, which further underscores the practical applicability of the sensor.

Optical nanosensors based on noble metal nanoclusters for detecting food contaminants: A review

Food contaminants present a significant threat to public health. In response to escalating global concerns regarding food safety, there is a growing demand for straightforward, rapid, and sensitive detection technologies. Noble metal nanoclusters (NMNCs) have garnered considerable attention due to their superior attributes compared to other optical materials. These attributes include high catalytic activity, excellent biocompatibility, and outstanding photoluminescence properties. These features render NMNCs promising candidates for crafting nanosensors for food contaminant detection, offering the potential for the development of uncomplicated, swift, sensitive, user-friendly, and cost-effective detection approaches. This review investigates optical nanosensors based on NMNCs, including the synthesis methodologies of NMNCs, sensing strategies, and their applications in detecting food contaminants. Furthermore, it involves a comparative assessment of the applications of NMNCs in optical sensing and their performance. Ultimately, this paper imparts fresh perspectives on the forthcoming challenges. Hitherto, optical (particularly fluorescent) nanosensors founded on NMNCs have demonstrated exceptional sensing capabilities in the realm of food contaminant detection. To enhance sensing performance, future research should prioritize atomically precise NMNCs synthesis, augmentation of catalytic activity and optical properties, development of high-throughput and multimode sensing, integration of NMNCs with microfluidic devices, and the optimization of NMNCs storage, shelf life, and transportation conditions.

Structure-activity relationship of drug conjugated polymeric materials against uropathogenic bacteria colonization under in vitro and in vivo settings

The human world has been plagued with different kinds of bacterial infections from time immemorial. The increased development of resistance towards commercial antibiotics has made these bacterial infections an even more critical challenge. Bacteria have modified their mode of interactions with different types of commercial drugs by bringing changes to the receptor proteins or by other resisting mechanisms like drug efflux. Various chemical approaches have been made to date to fight against these smart adapting species. Towards this, we hypothesize chemically modifying the commercial antibacterial drugs in order to deceive the bacteria and destroy the bacterial biomass. In this study, different molecular weight polyethyleneimines are taken and conjugated with some well-known commercial drugs like penicillin and chloramphenicol to explore their antibacterial properties against some of the laboratory and uro-pathogenic strains of Gram-positive and Gram-negative bacteria. A detailed structure-activity relationship of these polymeric prodrug-like materials has been evaluated to determine the optimum formulation. The standardized system not only shows significant ∼90% bacterial killing in liquid broth culture, but also demonstrates promising bacterial inhibition towards biofilm formation for the pathogenic strains on inanimate surfaces like urinary catheters and on an in vivo mouse skin abrasion model. The reported bioactive polymeric materials can be successfully used for widespread therapeutic applications with promising medical relevance.

Preparation of Biocidal Nanocomposites in X-ray Irradiated Interpolyelectolyte Complexes of Polyacrylic Acid and Polyethylenimine with Ag-Ions

Due to the presence of cationic units interpolyelectrolyte complexes (IPECs) can be used as a universal basis for preparation of biocidal coatings on different surfaces. Metallopolymer nanocomposites were successfully synthesized in irradiated solutions of polyacrylic acid (PAA) and polyethylenimine (PEI), and dispersions of non-stoichiometric IPECs of PAA–PEI containing silver ions. The data from turbidimetric titration and dynamic light scattering showed that pH 6 is the optimal value for obtaining IPECs. Metal polymer complexes based on IPEC with a PAA/PEI ratio equal to 3/1 and 1/3 were selected for synthesis of nanocomposites due to their aggregative stability. Studies using methods of UV–VIS spectroscopy and TEM have demonstrated that the size and spatial organization of silver nanoparticles depend on the composition of polymer systems. The average sizes of nanoparticles are 5 nm and 20 nm for complexes with a molar ratio of PAA/PEI units equal to 3/1 and 1/3, respectively. The synthesized nanocomposites were applied to the glass surface and exhibited high antibacterial activity against both gram-positive (Staphylococcus aureus) and gram-negative bacteria (Salmonella). It is shown that IPEC-Ag coatings demonstrate significantly more pronounced biocidal activity not only in comparison with macromolecular complexes of PAA–PEI, but also coatings of PEI and PEI based nanocomposites.

Silver Nanodot Decorated Dendritic Copper Foam As a Hydrophobic and Mechano-Chemo Bactericidal Surface

The present work investigates the time-dependent antibacterial activity of the silver nanodot decorated dendritic copper foam nanostructures against Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) bacteria. An advanced antibacterial and antifouling surface is fabricated utilizing the collective antibacterial properties of silver nanodots, chitosan, and dendritic copper foam nanostructures. The porous network of the Ag nanodot decorated Cu foam is made up of nanodendrites, which reduce the wettability of the surface. Hence, the surface exhibits hydrophobic nature and inhibits the growth of bacterial flora along with the elimination of dead bacterial cells. The fabricated surface exhibits a water contact angle (WCA) of 158.7 ± 0.17°. Specifically, we tested the fabricated material against both the Gram-positive and Gram-negative bacterial models. The antibacterial activity of the fabricated surface is evident from the growth inhibition percentage of bacterial strains of Escherichia coli (72.30 ± 0.60%) and Bacillus subtilis (48.30 ± 1.71%). The micrographs obtained from scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) of the treated cells show the damaged cellular structures of the bacteria, which is strong evidence of successful antibacterial action. The antibacterial effect can be attributed to the synergistic mechano-chemo mode of action involving mechanical disruption of the bacterial cell wall by the nanoprotrusions present on the Cu dendrites along with the chemical interaction of the Ag nanodots with vital intracellular components.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

Biocontamination of medical devices and implants is a growing issue that causes medical complications and increased expenses. In the fight against biocontamination, developing synthetic surfaces, which reduce the adhesion of microbes and provide biocidal activity or combinatory effects, has emerged as a major global strategy. Advances in nanotechnology and biological sciences have made it possible to design smart surfaces for decreasing infections. Nevertheless, the clinical performance of these surfaces is highly depending on the choice of material. This review focuses on the antimicrobial surfaces with functional material coatings, such as cationic polymers, metal coatings and antifouling micro-/nanostructures. One of the highlights of the review is providing insights into the virus-inactivating surface development, which might particularly be useful for controlling the currently confronted pandemic coronavirus disease 2019 (COVID-19). The nanotechnology-based strategies presented here might be beneficial to produce materials that reduce or prevent the transmission of airborne viral droplets, once applied to biomedical devices and protective equipment of medical workers. Overall, this review compiles existing studies in this broad field by focusing on the recent related developments, draws attention to the possible activity mechanisms, discusses the key challenges and provides future recommendations for developing new, efficient antimicrobial and antiviral surface coatings.

Chemical synthesis, inhibitory activity and molecular mechanism of 1-deoxynojirimycin–chrysin as a potent α-glucosidase inhibitor

Hyperglycemia can be efficaciously regulated by inhibiting α-glucosidase activity and this is regarded as an effective strategy to treat type 2 diabetes.

Antibiofilm and anti-quorum sensing activities of polyethylene imine coated magnetite and nickel ferrite nanoparticles

This study was aimed at synthesizing polyethyleneimine-coated magnetic nanoparticles and evaluating their effect on pathogenic bacteria. Polyethyleneimine-coated magnetite (PEIMnF) and nickel ferrite (PEINF) nanoparticles were succesfully synthesized and their surface groups, morphology and chemical structures were characterized using ATR-FTIR (Attenuated Total Reflectance Fourrier Transformed Infra-Red) and SEM (Scanning Electron Microscopy). TGA (Thermogravimetric analysis) was used to analyse the thermal behaviour and stability of synthesized nanomaterials. The minimal inhibitory concentration (MIC) values of the polyethylene imine coated magnetite and nickel ferrite nanomaterials against Staphylococcus aureus, Escherichia coli and Candida albicans was found to be 10 mg/mL. Both nanomaterials (PEIMnF and PEINF) showed very excellent and concentration-dependent biofilm inhibition especially at the highest test concentration of 10 mg/mL at which PEIMnF inhibited biofilm formation on E. coli (89.04 ± 0.50%), S. aureus (82.85 ± 2.42%) and C. albicans (91.37 ± 0.66%). At this concentration, PEINF equally inhibited biofilm formations of E. coli (90.48 ± 2.05%), S. aureus (87.04 ± 1.59%) and C. albicans (90.94 ± 1.03%). Only PEINF showed a concentration-dependent violacein inhibition with highest inhibition of 51.2 ± 3.5% at MIC and quorum sensing with inhibition zones of 16.3 ± 1.0 mm at MIC and 11.5 ± 0.5 mm at MIC/2 which could be attributed to the presence of nickel. The nanomaterials inhibited swimming and swarming motilities in Pseudomonas aeruginosa PA01 and it was found that at the same concentration, swimming inhibition was greater than swarming inhibitions and PEINF showed better inhibition than PEIMnF in both models. Polyethyleneimine-coated magnetite and nickel ferrite nanomaterials could be used in overcoming health problems associated with microbial infections and resistance.

Ratiometric and sensitive cyanide sensing using dual-emissive gold nanoclusters

The detection of cyanide anion (CN^-), a highly toxic pollutant, has attracted growing attention in the past years. In this work, a nanosensor composed of hyperbranched polyethyleneimine (hPEI)-assisted dual-emissive gold nanoclusters (DE-Au NCs) is proposed for ratiometric detection of CN^- based on surface valence state-driving etch. The ratiometric color change of fluorescence is based on a fact that the red-emissive Au NCs with a high content of surface Au(I) can be easily etched by CN^-, while the blue-emissive Au NCs with nearly neutral character can resist CN^-. Because of the specific gold-CN^- chemistry and electrostatic attraction between the positively charged hPEI protecting layer and the negatively charged CN^-, the DE-Au NC-based nanosensor provides high selectivity toward CN^- over other anions with a limit of detection of 10 nM. Practical application of the proposed DE-Au NC nanosensor is verified by satisfying recoveries of CN^- determination in river water and urine samples. Graphical abstract.

Combating Antibiotic Resistance through the Synergistic Effects of Mesoporous Silica-Based Hierarchical Nanocomposites

The enormous influence of bacterial resistance to antibiotics has led researchers toward the development of various advanced antibacterial modalities. In this vein, nanotechnology-based devices have garnered interest owing to their excellent morphological as well as physicochemical features, resulting in augmented therapeutic efficacy. Herein, to overcome the multidrug resistance (MDR) in bacteria, we demonstrate the fabrication of a versatile design based on the copper-doped mesoporous silica nanoparticles (Cu-MSNs). Indeed, the impregnated Cu species in the siliceous frameworks of MSNs establish pH-responsive coordination interactions with the guest molecules, tetracycline (TET), which not only enhance their loading efficiency but also assist in their release in the acidic environment precisely. Subsequently, the ultrasmall silver nanoparticles-stabilized polyethyleneimine (PEI-SNP) layer is coated over Cu-MSNs. The released silver ions from the surface-deposited SNPs are capable of sensitizing the resistant strains through establishing the interactions with the biomembranes, and facilitate the generation of toxic free radicals, damaging the bacterial components. In addition to SNPs, Cu species impregnated in MSN frameworks synergistically act through the production of free radicals by participating in the Fenton-like reaction. Various physical characterization techniques for confirming the synthesis and successful surface modification of functional nanomaterials, as well as different antibacterial tests performed against MDR bacterial strains, are highly commendable. Remarkably, this versatile formulation has shown no significant toxic effects on normal mammalian fibroblast cells accounting for its high biocompatibility. Together, these biocompatible MSN-based trio-hybrids with synergistic efficacy and pH-responsive delivery of antibiotics potentially allow for efficient combat against MDR in bacteria.

Study of the Intrinsic Fluorescence of a Highly Branched Cationic Dendrimer, Poly(Ethyleneimine) (PEI)

Poly(ethyleneimine) (PEI) is a weakly basic, synthetic, polycationic polymer, due to the presence of primary, secondary, and tertiary amino groups. The amino groups are responsible for the variety of applications of PEI (e.g., transfection, bioimaging, solar cell, etc.). Our study presents some new and reproducible methods for the quantification of molecular or mass concentration of highly branched PEI of different molecular weights (800–2000–25,000–750,000 MW PEI). In the course of the direct method, spectrophotometry and fluorometry were applied to determine the absorption and fluorescence of PEI dilution series. An increase in the MW at the same concentration produces a higher count number because of the higher number of amino groups in PEI molecules. The character of increment in fluorescence intensity is essentially different in the case of mass concentrations and molar concentrations. The increment of the fluorescence intensity related to the molar concentration is non-linear. In the case of mass concentration, the slope is linear. Moreover, their fluorescence is enhanced with the decrease in pH values. The spectrophotometry is a reliable method for measuring the quantity of PEI molecules in solution. Our data help in recognizing the detailed properties of PEI in dendrimer research.

Nanoantibiotics: A Novel Rational Approach to Antibiotic Resistant Infections

Background:

The main drawbacks for using conventional antimicrobial agents are the development of multiple drug resistance due to the use of high concentrations of antibiotics for extended periods. This vicious cycle often generates complications of persistent infections, and intolerable antibiotic toxicity. The problem is that while all new discovered antimicrobials are effective and promising, they remain as only short-term solutions to the overall challenge of drug-resistant bacteria.

Objective:

Recently, nanoantibiotics (nAbts) have been of tremendous interest in overcoming the drug resistance developed by several pathogenic microorganisms against most of the commonly used antibiotics. Compared with free antibiotic at the same concentration, drug delivered via a nanoparticle carrier has a much more prominent inhibitory effect on bacterial growth, and drug toxicity, along with prolonged drug release. Additionally, multiple drugs or antimicrobials can be packaged within the same smart polymer which can be designed with stimuli-responsive linkers. These stimuli-responsive nAbts open up the possibility of creating multipurpose and targeted antimicrobials. Biofilm formation still remains the leading cause of conventional antibiotic treatment failure. In contrast to conventional antibiotics nAbts easily penetrate into the biofilm, and selectively target biofilm matrix constituents through the introduction of bacteria specific ligands. In this context, various nanoparticles can be stabilized and functionalized with conventional antibiotics. These composites have a largely enhanced bactericidal efficiency compared to the free antibiotic.

Conclusion:

Nanoparticle-based carriers deliver antibiotics with better biofilm penetration and lower toxicity, thus combating bacterial resistance. However, the successful adaptation of nanoformulations to clinical practice involves a detailed assessment of their safety profiles and potential immunotoxicity.

Antibacterial Activity of Silver Nanoparticles: Structural Effects

The increase of antibiotic resistance in bacteria has become a major concern for successful diagnosis and treatment of infectious diseases. Over the past few decades, significant progress has been achieved on the development of nanotechnology-based medicines for combating multidrug resistance in microorganisms. Among this, silver nanoparticles (AgNPs) hold great promise in addressing this challenge due to their broad-spectrum and robust antimicrobial properties. This review illustrates the antibacterial mechanisms of silver nanoparticles and further elucidates how different structural factors including surface chemistry, size, and shape, impact their antibacterial activities, which are expected to promote the future development of more potent silver nanoparticle-based antibacterial agents.

Antimicrobial activity of nano-sized silver colloids stabilized by nitrogen-containing polymers: the key influence of the polymer capping

Synthesis of stable silver colloids was achieved using nitrogen-containing polymers acting simultaneously as a reducing and stabilizer agent. The polymers polyethyleneimine (PEI), polyvinylpyrrolidone (PVP) and poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PEO-b-P2VP) were used in the procedures. The influence of the surface chemistry and chemical nature of the stabilizer on the cytotoxicity and antimicrobial properties have been evaluated. The produced nanomaterials were found to be non-toxic up to the highest evaluated concentration (1.00 ppm). Nevertheless, at this very low concentration, the AgNPs stabilized by PVP and PEO-b-P2VP were found to be remarkable biocides against bacteria and fungus. On the other hand, we have surprisingly evidenced negligible antimicrobial activity of AgNPs stabilized by positively charged PEI although both (AgNPs and PEI) materials separately are known for their antimicrobial activity as also evidenced in the current investigation. The evidence is claimed to be related to the blocking of Ag+ kinetic release. Accordingly, the antimicrobial effect of nano-sized silver colloids largely depends on the chemical nature of the polymer coating. Possibly, the outstanding colloid stabilization provided by polyethyleneimine slows down Ag+ release thereby hampering its biological activity whereas the poorer stabilization and good ionic transport property of PVP and PEO-b-P2VP allows much faster ion release and cell damage.

Biointeractions of Herbicide Atrazine with Human Serum Albumin: UV-Vis, Fluorescence and Circular Dichroism Approaches

The herbicide atrazine is widely used across the globe, which is a great concern. To investigate its potential toxicity in the human body, human serum albumin (HSA) was selected as a model protein. The interaction between atrazine and HSA was investigated using steady-state fluorescence spectroscopy, synchronous fluorescence spectroscopy, UV-Vis spectroscopy, three-dimensional (3D) fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The intrinsic fluorescence of HSA was quenched by the atrazine through a static quenching mechanism. Fluorescence spectra at two excitation wavelengths (280 and 295 nm) showed that the fluorescence quenched in HSA was mainly contributed to by tryptophan residues. In addition, the atrazine bound to HSA, which induced changes in the conformation and secondary structure of HSA and caused an energy transfer. Thermodynamic parameters revealed that this binding is spontaneous. Moreover, electrostatic interactions play a major role in the combination of atrazine and HSA. One atrazine molecule can only bind to one HSA molecule to form a complex, and the atrazine molecule is bound at site II (subdomain IIIA) of HSA. This study furthers the understanding of the potential effects posed by atrazine on humans at the molecular level.

Optimization and integration of nanosilver on polycaprolactone nanofibrous mesh for bacterial inhibition and wound healing in vitro and in vivo

Bacterial infection is a major hurdle to wound healing, and the overuse of antibiotics have led to global issue, such as emergence of multidrug-resistant bacteria, even “super bacteria”. On the contrary, nanosilver (NS) can kill bacteria without causing resistant bacterial strains. In this study, NS was simply generated in situ on the polycaprolactone (PCL) nanofibrous mesh using an environmentally benign and mussel-inspired dopamine (DA). Scanning electron microscopy showed that NS uniformly formed on the nanofibers of PCL mesh. Fourier transform infrared spectroscopy revealed the step-by-step preparation of pristine PCL mesh, including DA coating and NS formation, which were further verified by water contact angle changing from hydrophobic to hydrophilic. To optimize the NS dose, the antibacterial activity of PCL/NS against Staphylococcus aureus, Escherichia coli and Acinetobacter baumannii was detected by bacterial suspension assay, and the cytotoxicity of NS was evaluated using cellular morphology observation and Cell Counting Kit-8 (CCK8) assay. Then, inductively coupled plasma atomic emission spectrometry exhibited that the optimized PCL/NS had a safe and sustained silver release. Moreover, PCL/NS could effectively inhibit bacterial infection in an infectious murine full-thickness skin wound model. As demonstrated by the enhanced level of proliferating cell nuclear antigen (PCNA) in keratinocytes and longer length of neo-formed epidermis, PCL/NS accelerated wound healing by promoting re-epithelialization via enhancing keratinocyte proliferation in infectious wounds.

Bioapplications of renal-clearable luminescent metal nanoparticles

This review summarizes the recent synthetic strategies of the renal-clearable luminescent metal nanoparticles, and discusses the biological behaviors and current disease-related applications of this type of biomaterials in tumor targeting, kidney disease and antimicrobial investigations.

Fluorescent metal quantum clusters: an updated overview of the synthesis, properties, and biological applications

A brief history of metal quantum clusters, their synthesis methods, physical properties, and an updated overview of their applications is provided.