Cytotoxicity studies and antibacterial modification of poly(ethylene 2,5-furandicarboxylate) nonwoven

Novel poly(ethylene 2,5-furandicarboxylate) PEF nonwovens were produced by solution electrospinning and further modification. To improve the wettability of the hydrophobic nonwovens with water, they were treated with sodium hydroxide. Cytotoxicity tests carried out with human keratinocytes confirmed that the nonwovens did not have a toxic effect on healthy cells. The hydrophilicity of the sodium hydroxide treated nonwoven favored the adherence of the cells and their growth. In turn, the two-step modification of the nonwovens by reactions with (3-mercaptopropyl)methyldimethoxysilane and silver nitrate permitted to deposit silver particles on the fiber surfaces. The bacteria growth inhibition zones around the tested specimens were observed evidencing their antibacterial activity against Escherichia coli and Staphylococcus aureus.

Electrical Conductivity and Antibacterial Activity of Woven Fabrics through Quercetin-Assisted Thermal Reduction of a Graphene Oxide Coating

Cotton and poly(ethylene terephthalate) (PET) woven fabrics were coated with graphene oxide (GO) using a padding method and the GO deposited on the fiber surfaces was thermally reduced to impart electrical conductivity to the fabrics. To assist the thermal reduction of GO, quercetin (Q)-a natural flavonoid-was used. To this end, before the reduction, the GO-padded fabrics were immersed in Q solutions in ethanol with different Q concentrations. Q enhanced the thermal reduction of GO. Depending on the Q concentration in the solutions, electrical surface resistivities of the cotton fabric of 750 kΩ/sq to 3.3 MΩ/sq and of the PET fabric of 240 kΩ/sq to 730 kΩ/sq were achieved. The cotton and PET fabrics also became hydrophobic, with water contact angles of 163° and 147°, respectively. In addition to the electrical conductivity, the presence of Q resulted in antibacterial activity of the fabrics against Escherichia coli and Staphylococcus aureus.

Inserting Menthoxytriazine into Poly(ethylene terephthalate) for Inhibiting Microbial Adhesion

Antimicrobial modification of poly(ethylene terephthalate) (PET) is effective in preventing the adhesion and growth of microorganisms on its surface. However, few methods are available to modify PET directly at its backbone to impart the antimicrobial effect. Herein, menthoxytriazine-modified PET (PMETM) based on the stereochemical antimicrobial strategy was reported. This novel PET was prepared by inserting menthoxytriazine into the PET backbone. The antibacterial adhesion test and the antifungal landing test were employed to confirm the antiadhesion ability of PMETM. PMETM could effectively inhibit the adhesion of bacteria, with inhibition ratios of 99.9 and 99.7% against Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive), respectively. In addition, PMETM exhibited excellent resistance to Aspergillus niger (fungal) contamination for more than 30 days. Cytotoxicity assays indicated that PMETM was a noncytotoxic material. These results suggested that the insertion of menthoxytriazine in the PET backbone was a promising strategy to confer antimicrobial properties to PET.

Synthetic Antimicrobial Polymers in Combination Therapy: Tackling Antibiotic Resistance

Antibiotic resistance is a critical global healthcare issue that urgently needs new effective solutions. While small molecule antibiotics have been safeguarding us for nearly a century since the discovery of penicillin by Alexander Fleming, the emergence of a new class of antimicrobials in the form of synthetic antimicrobial polymers, which was driven by the advances in controlled polymerization techniques and the desire to mimic naturally occurring antimicrobial peptides, could play a key role in fighting multidrug resistant bacteria in the near future. By harnessing the ability to control chemical and structural properties of polymers almost at will, synthetic antimicrobial polymers can be strategically utilized in combination therapy with various antimicrobial coagents in different formats to yield more potent (synergistic) outcomes. In this review, we present a short summary of the different combination therapies involving synthetic antimicrobial polymers, focusing on their combinations with nitric oxide, antibiotics, essential oils, and metal- and carbon-based inorganics.

Multivalent and synergistic chitosan oligosaccharide-Ag nanocomposites for therapy of bacterial infection

Chitosan oligosaccharide functionalized silver nanoparticles with synergistic bacterial activity were constructed as a multivalent inhibitor of bacteria. Placing the chitosan oligosaccharide on silver nanoparticles can dramatically enhance the adsorption to the bacterial membrane via multivalent binding. The multicomponent nanostructures can cooperate synergistically against gram-positive and gram-negative bacteria. The antibacterial activity was increased via orthogonal array design to optimize the synthesis condition. The synergistic bacterial activity was confirmed by fractional inhibitory concentration and zone of inhibition test. Through studies of antimicrobial action mechanism, it was found that the nanocomposites interacted with the bacteria by binding to Mg²⁺ ions of the bacterial surface. Then, the nanocomposites disrupted bacterial membrane by increasing the permeability of the outer membrane, resulting in leakage of cytoplasm. This strategy of chitosan oligosaccharide modification can increase the antibacterial activity of silver nanoparticles and accelerate wound healing at the same time. The nanomaterial without cytotoxicity has promising applications in bacteria-infected wound healing therapy.

Mussel-inspired coordination functional polymer brushes-decorated rGO-stabilized silver nanoparticles composite for antibacterial application

A catechol-terminated coordination functional polymer-modified rGO supported AgNPs composite was fabricated. Grafted polymer brushes improve the material's hydrophilicity and dispersion stability of AgNPs on rGO, enhancing antibacterial activity.

Combinations of Antimicrobial Polymers with Nanomaterials and Bioactives to Improve Biocidal Therapies

The rise of antibiotic-resistant microorganisms has become a critical issue in recent years and has promoted substantial research efforts directed to the development of more effective antimicrobial therapies utilizing different bactericidal mechanisms to neutralize infectious diseases. Modern approaches employ at least two mixed bioactive agents to enhance bactericidal effects. However, the combinations of drugs may not always show a synergistic effect, and further, could also produce adverse effects or stimulate negative outcomes. Therefore, investigations providing insights into the effective utilization of combinations of biocidal agents are of great interest. Sometimes, combination therapy is needed to avoid resistance development in difficult-to-treat infections or biofilm-associated infections treated with common biocides. Thus, this contribution reviews the literature reports discussing the usage of antimicrobial polymers along with nanomaterials or other inhibitors for the development of more potent biocidal therapies.

Synthesis of photothermal nanocomposites and their application to antibacterial assays

In this work, we report a novel gold nanorod (AuNR)-based nanocomposite that shows strong binding to bacterium and high antibacterial efficiency. The AuNRs were used as a photothermal material to transform near-infrared radiation (NIR) into heat. We selected poly (acrylic acid) to modify the surface of the AuNRs based on a simple self-assembly method. After conjugation of the bacterium-binding molecule vancomycin, the nanocomposites were capable of efficiently gathering on the cell walls of bacteria. The nanocomposites exhibited a high bacterial inhibition capability owing to NIR-induced heat generation in situ. Therefore, the prepared photothermal nanocomposites show great potential for use in antibacterial assays.

Antimicrobial mechanisms due to hyperpolarisation induced by nanoporous Au

Nanomaterials such as nanoparticles exhibit remarkable antimicrobial activities. Nanoparticles directly disturb the cell membrane or cytoplasmic proteins because they pass through the cell wall. Nanoporous Au (NPG) is another antimicrobial nanomaterial, which cannot pass through the cell wall of bacteria but can still kill bacteria, utilising interactions between the surface of NPG and cell wall of bacteria. The origins of antimicrobial activities without direct interactions are unknown. It is necessary to elucidate these mechanisms to ensure safe usage. Here we show that the antimicrobial mechanism of NPG consists of two interactions: between the surface of NPG and cell wall, and between the cell wall and cell membrane. Fluorescent experiments showed that the cell wall was negatively hyperpolarised by NPG, and molecular dynamics simulations and first-principles calculations suggested that the hyperpolarisation of the cell wall leads to delicate structural changes in the membrane proteins, rendering them bactericidal. Thus, the hyperpolarisation induced by NPG plays a critical role in both interactions. The combination of molecular dynamics simulations and first-principles calculations allows a deeper understanding of the interactions between metallic surfaces and biomolecules, because charge transfer and exchange interactions are calculated exactly.

Multivalent Antimicrobial Polymer Nanoparticles Target Mycobacteria and Gram-Negative Bacteria by Distinct Mechanisms

Because of the emergence of antimicrobial resistance to traditional small-molecule drugs, cationic antimicrobial polymers are appealing targets. Mycobacterium tuberculosis is a particular problem, with multi- and total drug resistance spreading and more than a billion latent infections globally. This study reports nanoparticles bearing variable densities of poly(dimethylaminoethyl methacrylate) and the unexpected and distinct mechanisms of action this multivalent presentation imparts against Escherichia coli versus Mycobacterium smegmatis (model of M. tuberculosis), leading to killing or growth inhibition, respectively. A convergent "grafting to" synthetic strategy was used to assemble a 50-member nanoparticle library, and using a high-throughput screen identified that only the smallest (2 nm) particles were stable in both saline and complex cell media. Compared with the linear polymers, the nanoparticles displayed two- and eight-fold enhancements in antimicrobial activity against M. smegmatis and E. coli, respectively. Mechanistic studies demonstrated that the antimicrobial particles were bactericidal against E. coli due to rapid disruption of the cell membranes. Conversely, against M. smegmatis the particles did not lyse the cell membrane but rather had a bacteriostatic effect. These results demonstrate that to develop new polymeric antituberculars the widely assumed, broad spectrum, membrane-disrupting mechanism of polycations must be re-evaluated. It is clear that synthetic nanomaterials can engage in more complex interactions with mycobacteria, which we hypothesize is due to the unique cell envelope at the surface of these bacteria.

Graphene sponge decorated with copper nanoparticles as a novel bactericidal filter for inactivation of Escherichia coli

Nanotechnology has great potential in water purification. However, the limitations such as aggregation and toxicity of nanomaterials have blocked their practical application. In this work, a novel copper nanoparticles-decorated graphene sponge (Cu-GS) was synthesized using a facile hydrothermal method. Cu-GS consisting of three-dimensional (3D) porous graphene network and well-dispersed Cu nanoparticles exhibited high antibacterial efficiency against Esherichia coli when used as a bactericidal filter. The morphological changes determined by scanning electron microscope and fluorescence images measured by flow cytometry confirmed the involvement of membrane damage induced by Cu-GS in their antibacterial process. The oxidative ability of Cu-GS and intercellular reactive oxygen species (ROS) were also determined to elucidate the possible antibacterial mechanism of Cu-GS. Moreover, the concentration of released copper ions from Cu-GS was far below the drinking water standard, and the copper ions also have an effect on the antibacterial activity of Cu-GS. Results suggested that Cu-GS as a novel bactericidal filter possessed a potential application of water disinfection.

Hydrophilic Phage-Mimicking Membrane Active Antimicrobials Reveal Nanostructure-Dependent Activity and Selectivity

The prevalent wisdom on developing membrane active antimicrobials (MAAs) is to seek a delicate, yet unquantified, cationic-hydrophobic balance. Inspired by phages that use nanostructured protein devices to invade bacteria efficiently and selectively, we study here the antibiotic role of nanostructures by designing spherical and rod-like polymer molecular brushes (PMBs) that mimic the two basic structural motifs of bacteriophages. Three model PMBs with different well-defined geometries consisting of multiple, identical copies of densely packed poly(4-vinyl-N-methylpyridine iodide) branches are synthesized by controlled/"living" polymerization, reminiscent of the viral structural motifs comprised of multiple copies of protein subunits. We show that, while the individual linear-chain polymer branch that makes up the PMBs is hydrophilic and a weak antimicrobial, amphiphilicity is not a required antibiotic trait once nanostructures come into play. The nanostructured PMBs induce an unusual topological transition of bacterial but not mammalian membranes to form pores. The sizes and shapes of the nanostructures further help define the antibiotic activity and selectivity of the PMBs against different families of bacteria. This study highlights the importance of nanostructures in the design of MAAs with high activity, low toxicity, and target specificity.

Hydrogel degradation triggered by pH for the smart release of antibiotics to combat bacterial infection

pH-Triggered smart drug release for the treatment of bacterial infection.

Vancomycin-hybrid bimetallic Au/Ag composite nanoparticles: preparation of the nanoparticles and characterization of the antibacterial activity

The Bimetallic Au/Ag composite nanoparticles have enhanced antibacterial activity and weak bacterial resistance.

Preparation of Hybrid Gold/Polymer Nanocomposites and Their Application in a Controlled Antibacterial Assay

In this work, we report a photosensitizer-loaded hybrid nanostructure that shows high antibacterial efficiency after surface interaction with a lectin protein. Gold nanoparticles were generated on the polymer nanoparticle surface through an in situ reduction method and behaved as a plasmonic amplifier. After conjugation of the photosensitizer rose bengal onto the hybrid nanoparticles, higher phosphorescence intensity and generation of reactive oxygen species (ROS) were observed. The nanocomposites showed high antibacterial efficiency toward Gram-negative Escherichia coli treated with a lectin protein concanavalin A, which caused self-assembly of the bacteria and nanoparticles. Therefore, the as-prepared nanostructure considerably improved the effectiveness of ROS toward bacteria and provides an alternative strategy for controlled antibacterial assays.

Recyclable Escherichia coli-Specific-Killing AuNP-Polymer (ESKAP) Nanocomposites

Escherichia coli plays a crucial role in various inflammatory diseases and infections that pose significant threats to both human health and the global environment. Specifically inhibiting the growth of pathogenic E. coli is of great and urgent concern. By modifying gold nanoparticles (AuNPs) with both poly[2-(methacrylamido)glucopyranose] (pMAG) and poly[2-(methacryloyloxy)ethyl trimethylammonium iodide] (pMETAI), a novel recyclable E. coli-specific-killing AuNP-polymer (ESKAP) nanocomposite is proposed in this study, which based on both the high affinity of glycopolymers toward E. coli pili and the merits of antibacterial quaternized polymers attached to gold nanoparticles. The properties of nanocomposites with different ratios of pMAG to pMETAI grafted onto AuNPs are studied. With a pMAG:pMETAI feed ratio of 1:3, the nanocomposite appeared to specifically adhere to E. coli and highly inhibit the bacterial cells. After addition of mannose, which possesses higher affinity for the lectin on bacterial pili and has a competitive advantage over pMAG for adhesion to pili, the nanocomposite was able to escape from dead E. coli cells, becoming available for repeat use. The recycled nanocomposite retained good antibacterial activity for at least three cycles. Thus, this novel ESKAP nanocomposite is a promising, highly effective, and readily recyclable antibacterial agent that specifically kills E. coli. This nanocomposite has potential applications in biological sensing, biomedical diagnostics, biomedical imaging, drug delivery, and therapeutics.

Amphiphilic cationic copolymers with ciprofloxacin: preparation and antimicrobial activities

Amphiphilic copolymers with ciprofloxacin and primary amine salt copolymers applied to cellulose fibers showed excellent antimicrobial activities.

Nanomaterial with high antimicrobial efficacy--copper/polyaniline nanocomposite

This study explores different mechanisms of antimicrobial action by designing hybrid nanomaterials that provide a new approach in the fight against resistant microbes. Here, we present a cheap copper-polyaniline (Cu-PANI) nanocomposite material with enhanced antimicrobial properties, prepared by simple in situ polymerization method, when polymer and metal nanoparticles are produced simultaneously. The copper nanoparticles (CuNPs) are uniformly dispersed in the polymer and have a narrow size distribution (dav = 6 nm). We found that CuNPs and PANI act synergistically against three strains, Escherichia coli, Staphylococcus aureus, and Candida albicans, and resulting nanocomposite exhibits higher antimicrobial activity than any component acting alone. Before using the colony counting method to quantify its time and concentration antimicrobial activity, different techniques (UV-visible spectroscopy, transmission electron microscopy, scanning electron microscope, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrophotometry, and inductively coupled plasma optical emission spectrometry) were used to identify the optical, structural, and chemical aspects of the formed Cu-PANI nanocomposite. The antimicrobial activity of this nanocomposite shows that the microbial growth has been fully inhibited; moreover, some of the tested microbes were killed. Atomic force microscopy revealed dramatic changes in morphology of tested cells due to disruption of their cell wall integrity after incubation with Cu-PANI nanocomposite.

Composite copolymer hybrid silver nanoparticles: preparation and characterization of antibacterial activity and cytotoxicity

The AgNPs could adhere to the bacterial membrane through electrostatic force, then damage the bacterial membrane irreversibly and lead to bacterial apoptosis finally.

Improving the protein activity and stability under acidic conditions via site-specific conjugation of a pH-responsive polyelectrolyte

Maintaining the protein activity and stability under acidic conditions is important in bioengineering and biomedical applications. Polyelectrolyte conjugation as a means of stabilizing proteins has received much recent attention. Retention of protein activity, and especially, improvement of protein stability by minimizing the number of polymer chains in the conjugate, as well as by choosing the optimal site for conjugation, is critical in practical applications. In this research, the cationic polyelectrolyte poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) was conjugated to the inorganic pyrophosphatase (PPase) site specifically. Conjugation of pDMAEMA to the specific site N124 on the protein surface led to a significant increase in activity at acidic pH. At pH 4.0, the activity of the pDMAEMA-conjugated protein was increased 3-fold relative to the unconjugated one. Dynamic light scattering (DLS) measurements showed that the aggregation state of the protein depended on the polymer charge as the pH was varied. Protein aggregation at low pH was prevented by pDMAEMA conjugation, resulting in an increase in protein stability under acidic conditions. The conjugate retained 60% of its initial activity after 4 h at pH 4.0, whereas the unconjugated protein lost 40% of its initial activity within 15 min at this pH. These results suggest an approach for preserving the protein activity and stability at low pH based on site-specific polyelectrolyte conjugation to the protein surface, thereby providing a new strategy for expanding the use of proteins in an acidic environment.

Biocatalytic and antimicrobial activities of gold nanoparticles synthesized by Trichoderma sp

The aim of this work was to synthesize gold nanoparticles by Trichoderma viride and Hypocrea lixii. The biosynthesis of the nanoparticles was very rapid and took 10 min at 30 °C when cell-free extract of the T. viride was used, which was similar by H. lixii but at 100 °C. Biomolecules present in cell free extracts of both fungi were capable to synthesize and stabilize the formed particles. Synthesis procedure was very quick and environment friendly which did not require subsequent processing. The biosynthesized nanoparticles served as an efficient biocatalyst which reduced 4-nitrophenol to 4-aminophenol in the presence of NaBH₄ and had antimicrobial activity against pathogenic bacteria. To the best of our knowledge, this is the first report of such rapid biosynthesis of gold nanoparticles within 10 min by Trichoderma having plant growth promoting and plant pathogen control abilities, which served both, as an efficient biocatalyst, and a potent antimicrobial agent.