Enhanced Antimicrobial Activity of Amine-Phosphonium (N-P) Hybrid Polymers Against Gram-Negative and Gram-Positive Bacteria

The authors report synthesis, characterization and evaluation of a series of linear polyethylenimine (lPEI)-grafted butyltriphenylphosphonium bromide (LBTP) polymers (N-P hybrid polymers) for their antimicrobial activity on various Gram-positive and Gram-negative bacteria. Polymers with ～5.8–13.8% substitution of butyltriphenylphosphonium bromide (BTP) on the backbone of lPEI showed enhanced charge density as compared to native lPEI confirming the conjugation of BTP onto lPEI. These modified polymers displayed low hemolytic activity and excellent antimicrobial activity against these two types of bacteria with one of the modified polymers, LBTP-40, was found to exhibit high antimicrobial activity in all the strains.     

Preparation of highly dispersed gold nanoparticles inside the porous support assisted by amphiphilic vinyl maleate copolymer

An amphiphilic copolymer composed of maleic acid and alkyl (C₁₈) vinyl monomer was encapsulated into the porous support. A series of colloidal gold nanoparticles of known size was substantially immobilized in the composite porous supports based on cross-linked polyacrylate ester and cross-linked polystyrene resin. Maleic acid moiety of the amphiphilic copolymer can act as a stabilizer for gold nanoparticles in analogy to citric acid, whereas alkyl chains play a role for the stable accommodation of the amphiphilic copolymer. Maleic acid stabilizes the gold nanoparticles by flexing the geometrical arrangement of the linear polymer. Presence of C₁₈ alkyl chain in the poly(C₁₈-vinyl maleate) is indispensable to act as spacing group that prevents mutual aggregation of gold nanoparticles. On the other hand, gold nanoparticles with average diameter of less than 8 nm were spontaneously formed by treatment of the composite resin beads with aqueous HAuCl₄ solution, subsequently dispersed inside the pores of resin beads as observed by TEM. We have also elucidated the catalytic activity of the material with the hydrogenation of cinnamaldehyde in supercritical carbon dioxide. Notably, apparent size effect of gold was observed in the selectivity of the reaction.     

Polymer–gold nanoparticle composite films for topical application: Evaluation of physical properties and antibacterial activity

The biocompatible polymer films show potential as an alternative to gels and patches used for topical delivery of therapeutics and cosmetics. The physical strength and antimicrobial activity of polymer films are important attributes for their topical applicability. Here, we have investigated the physical properties and antibacterial activity of six commonly used film forming polymers before and after formation of nanocomposites with gold nanoparticles (AuNP). The blank and AuNP loaded polymer films were prepared by solvent casting method and characterized for thickness, tensile strength, burst strength, skin adhesion strength, degree of swelling, and porosity. The antibacterial activity of the composite films was evaluated by zone‐of‐inhibition and spectrophotometric growth inhibition method against Staphylococcus aureus and Escherichia coli . The physical characterization showed that chitosan films casted using 1.5% w/w resulted in 76 MPa of tensile strength, while zein films required 40% w/w to show 23 MPa of tensile strength. The AuNP (250 μM; 35 nm) loaded polymer films showed significantly (p < 0.05) greater burst strength and skin adhesion strength compared with respective blank films. Among the polymers tested, only blank films of chitosan and zein showed antibacterial activity. On the other hand, all the AuNP loaded polymer films showed significantly (p < 0.05) greater antibacterial activity. The AuNP loaded chitosan film showed E. coli growth inhibition similar to tetracycline. Taken together, chitosan‐ and zein‐AuNP nanocomposite films showed better physical properties and antibacterial activity. POLYM. COMPOS., 38:2829–2840, 2017. © 2015 Society of Plastics Engineers     

Drag reduction and molecular structure. The interaction of polyethylenimine with some linear high polymers

The structure of polyethylenimine in aqueous and ethanolic solutions was investigated by measuring the fluorescence polarization of dansyl conjugates. In aqueous solutions, all polyethylenimines, whatever their molecular weight, are associated into large aggregates containing rotating units having rotary relaxation times corresponding to spherical particles of molecular weight about 3–6 × 10³. The interaction of polyethylenimine with very dilute solutions of linear high polymers has been investigated by fluorescence polarization measurements and by the measurement of turbulent drag. Addition of polyethylenimine causes the solutions of anionic polymers to lose their capability of reducing turbulent drag. The results are discussed in relation to the proposed structure of the anionic–cationic complexes formed in the mixtures.     

Spectroscopic and Antibacterial Evaluation of Nano-Hydroxapatite Polyvinyl Alcohol Biocomposite Doped with Microbial-Synthesized Nanogold for Biomedical Applications

Gold nanoparticles were synthesized by locally isolated fungi, Eurotium herbariorum. The biosynthesized nanogold was estimated by color change after the addition of fungal biomass to an aqueous solution of HAuCl₄ (1 g/L). Transmission electron microscopy (TEM) evaluated that the biosynthesized gold nanoparticles exhibited size range between 15 and 34 nm. Hydroxyapatite/polyvinylalcohol biocomposite containing fungal biosynthesized gold nanoparticles at different concentrations were studied for using in biomedical applications. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) studies test the physical and chemical characteristics of the biocomposite. The biocomposite containing nanogold showed antibacterial activity that increased with nanogold concentration.     

Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration

Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both gram negative (Escherichia coli and Pseudomonas aeruginosa) and gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure.     

Analytical detection and biological assay of antileukemic drug using gold nanoparticles

Gold nanoparticles are reported and evaluated as probes for the detection of anticancer drug 6-mercaptopurine (6-MP). The nature of binding between 6-MP and the gold nanoparticles via complexation is investigated using ultraviolet-visible spectrum, cyclic voltammetry, transmission electron microscopy, fluorescence and Fourier transform infrared (FT-IR) spectroscopy. The bound antileukemic drug is fluorescent and the quenching property of gold nanoparticles could be exploited for biological investigations. The 6-MP-colloidal gold complex is observed to have appreciable antibacterial and antifungal activity against Micrococcus luteus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Aspergillus fumigatus, and Aspergillus niger. The experimental studies suggest that gold nanoparticles have the potential to be used as effective carriers for anticancer drugs.     

On the Enhanced Antibacterial Activity of Antibiotics Mixed with Gold Nanoparticles

The bacterial action of gentamicin and that of a mixture of gentamicin and 15-nm colloidal-gold particles on Escherichia coli K12 was examined by the agar-well-diffusion method, enumeration of colony-forming units, and turbidimetry. Addition of gentamicin to colloidal gold changed the gold color and extinction spectrum. Within the experimental errors, there were no significant differences in antibacterial activity between pure gentamicin and its mixture with gold nanoparticles (NPs). Atomic absorption spectroscopy showed that upon application of the gentamicin-particle mixture, there were no gold NPs in the zone of bacterial-growth suppression in agar. Yet, free NPs diffused into the agar. These facts are in conflict with the earlier findings indicating an enhancement of the bacterial activity of similar gentamicin–gold nanoparticle mixtures. The possible causes for these discrepancies are discussed, and the suggestion is made that a necessary condition for enhancement of antibacterial activity is the preparation of stable conjugates of NPs coated with the antibiotic molecules.     

Polyelectrolyte‐aided synthesis of gold and platinum nanoparticles: Implications in electrocatalysis and sensing

An electrochemical method for depositing redispersible, lower size gold nanoparticles from a novel polyelectrolyte‐gold complex is described. The size of gold nanoparticles is in the range 6.2–15.4 nm. The gold nanoparticles, first deposited on platinum surface are transferable into water. They can also be directly in situ‐electrodeposited on to materials like carbon, carbon nanotubes or conducting polymers for an end use as electro catalysts. The composites Au‐MWCNT, Pt‐MWCNT, Au‐Carbon, and Pt‐Carbon are synthesized and tested for their electrocatalytic activity. The composites exhibit good catalytic activity in sensing dopamine or electrooxidation of methanol. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical,biological, and antibacterial characterization of silica glass containing silver and gold nanoparticles

The aim of this study has been the preparation of sol‐gel glasses with potential antibacterial properties. Bioactive glasses containing different percentages of silver and gold nanoparticles have been synthesized via the sol‐gel method. The obtained glasses have 0.5, 1, 1.5, and 2 wt% silver as well as a constant amount of gold nanoparticles (AuNP) added as colloidal solution (15 wt%). Fourier Transform Infrared (FTIR) spectroscopy was used to characterize the materials. Scanning electron microscopy (SEM) has been used to investigate the surface of each sample. Moreover, the materials have been characterized in order to verify their antibacterial activities as well as their bioactivity and cytocompatibility as a function of Ag and Au content. SEM/EDX analysis has shown that the samples are bioactive because they are able to stimulate hydroxyapatite nucleation on their surface when soaked in a simulated body fluid (SBF). WST‐8 assay of 3T3 cells, placed in contact with the material extracts, has showed that the glass does not induce cytotoxicity. Staphylococcus epidermidis and Pseudomonas aeruginosa strains have been used for the evaluation of the antibacterial properties of each sample. The experimental data have shown that all synthesized materials have antibacterial activity. However, the two bacterial strains respond differently to the materials. The data show that the presence of AuNP causes a decrease in the antibacterial activity of Ag⁺ ions.     

Boric acid recovery using polymer filtration: Studies with alkyl monool,diol, and triol containing polyethylenimines

Three water‐soluble polymers containing linear alkyl monool, 1,2‐diol, and 1,2,3‐triol groups, mostly on the primary amines of polyethylenimine, were synthesized, characterized, and tested for their ability to recover boric acid. The boron‐binding capacities of these polymers and the backbone polyethylenimine were determined by titration, ultrafiltration, and inductively coupled plasma/atomic emission spectroscopy analysis. At low boron concentrations, the 1,2,3‐triol polymer performed better than the 1,2‐diol, whereas at high boron concentrations, the 1,2‐diol outperformed the 1,2,3‐triol. ¹¹B‐NMR spectroscopy and retention studies with various salt concentrations indicated that boron interacted with these two polymers by means of ion pairing with the protonated amines and by borate ester formation. For the monool and the polyethylenimine backbone, the mechanism for boron binding was ion pairing only. These polymers are under consideration for the selective recovery and recycling of enriched boric acid used in the primary coolant loop of pressurized water nuclear reactors. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1590–1604, 2005     

Design and Synthesis of Ionic Liquid-Based Matrix Metalloproteinase Inhibitors (MMPIs): A Simple Approach to Increase Hydrophilicity and to Develop MMPI-Coated Gold Nanoparticles

Selective and potent matrix metalloproteinase 12 (MMP-12) inhibitors endowed with improved hydrophilicity are highly sought for potential use in the treatment of lung and cardiovascular diseases. In the present paper, we modified the structure of a nanomolar MMP-12 inhibitor by incorporating an ionic liquid (IL) moiety to improve aqueous solubility. Four biologically active salts were obtained by linking the sulfonamide moiety of the MMP-12 inhibitor to imidazolium-, pyrrolidinium-, piperidinium-, and DABCO-based ILs. The imidazolium-based bioactive salt was tested on human recombinant MMPs and on monocyte-derived dendritic cells, showing activity similar to that of the parent compound, but improved water solubility. The imidazolium-based bioactive salt was then used to prepare electrostatically stabilized MMP inhibitor-coated gold nanoparticles (AuNPs) able to selectively bind MMP-12. These AuNPs were used to study subcellular localization of MMP-12 in monocyte-derived dendritic cells by transmission electron microscopy analysis.     

Recent Advances in Amphiphilic Polymers as the Stabilizers of Colloidal Gold Nanoparticles

Gold nanoparticles (AuNPs) exhibit high catalytic activity as catalysts and have potential applications in biomedicine. To prevent the aggregation of colloidal AuNPs, the stabilizers including organic small molecules, organic ligands, inorganic ligands, and polymers, are necessary to be added in the synthesis of colloidal AuNPs. Among these stabilizers, amphiphilic polymers have attracted significant attention from scientists in the development of polymerization and modification methods. To date, numerous efforts are employed to develop amphiphilic polymers as the stabilizers of colloidal AuNPs but are not well‐summarized yet. In this review, four parts (amphiphilic linear polymers, amphiphilic graft polymers, amphiphilic hyperbranched polymers, and amphiphilic dendrimers) according to the polymer architectures will be discussed. Comprehensive understanding of amphiphilic polymers that are used for stabilizing colloidal AuNPs is provided.     

PEI-assisted preparation of Au nanoparticles via reductive crystallization process

Nano-sized gold particles were prepared in a solution containing polyethylenimine (PEI) utilizing a batch reactor. PEI acts as a reducing agent as well as a stabilizing agent of nanoparticles. The effects of initial concentration of PEI on the mean particle diameter, coefficient of variation (C.V.), growth rate, nucleation rate and the number of nuclei were studied. The particle diameter of gold decreased markedly with increasing initial concentration of PEI, from 3.3 μm to a minimum value of about 5 nm. The observed decrease of particle diameter was considered to be caused by the growth-inhibiting effect of PEI, which affects the conclusive number of nuclei.     

Antibacterial activity of natural polymer gels and potential applications without synthetic antibiotics

Antibiotics' use has increased, resulting in disadvantages like patients' drug resistance. Consequently, urgent action is required to develop a new generation of antibacterial agents. Most antibacterial platforms still require a modification with further antibacterial agents (e.g., antibiotics) for adequate antibacterial efficiency. Thus, a nonantibiotic methodology is immediately needed. Furthermore, bactericidal agents used for this purpose are usually based on metal nanoparticles, carbon materials, and polymers. Still, chemicals, antibiotics, and biocides lead to environmental damage. Therefore, the help of biocompatible yet durable materials and polymers is highly appreciated. In addition, if a polymer is not biodegradable, it will remain in the environment for more than one hundred years due to its low degradation rate. Moreover, non-biodegradable polymers are harmful to in vivo applications. Hence, the use of biodegradable and non-toxic materials has received many considerations. Over the last few years, the design and synthesis of new polymer gels have gained increasing attention. A polymer gel, also known as a hydrogel, is a three-dimensional and cross-linked network filled with water or other liquid solvents. Besides, the hydrogels supercritical drying method results in aerogels, and the freeze-drying method generates cryogels, where their porous and sponge-like structures are preserved. Additionally, antibacterial polymer gels are a new generation of polymers considered attractive due to their unique properties. The most recent studies and the latest innovations in polymer gels and hybrid polymers with intrinsic antibacterial properties were discussed in the present review. The reviewed studies from 2015 to April 2022 showed a tremendous revival in research about biopolymer hydrogel, aerogel, and cryogel as antibacterial agents.     

Gold nanoparticle-based electrochemical biosensors

The unique properties of gold nanoparticles to provide a suitable microenvironment for biomolecules immobilization retaining their biological activity, and to facilitate electron transfer between the immobilized proteins and electrode surfaces, have led to an intensive use of this nanomaterial for the construction of electrochemical biosensors with enhanced analytical performance with respect to other biosensor designs. Recent advances in this field are reviewed in this article. The advantageous operational characteristics of the biosensing devices designed making use of gold nanoparticles are highlighted with respect to non-nanostructured biosensors and some illustrative examples are commented. Electrochemical enzyme biosensors including those using hybrid materials with carbon nanotubes and polymers, sol-gel matrices, and layer-by-layer architectures are considered. Moreover, electrochemical immunosensors in which gold nanoparticles play a crucial role in the electrode transduction enhancement of the affinity reaction as well as in the efficiency of immunoreagents immobilization in a stable mode are reviewed. Similarly, recent advances in the development of DNA biosensors using gold nanoparticles to improve DNA immobilization on electrode surfaces and as suitable labels to improve detection of hybridization events are considered. Finally, other biosensors designed with gold nanoparticles oriented to electrically contact redox enzymes to electrodes by a reconstitution process and to the study of direct electron transfer between redox proteins and electrode surfaces have also been treated.     

INORGANIC NANOPARTICLES AS OPTICALLY EFFECTIVE ADDITIVES FOR POLYMERS

The transparency of polymer-particle composites can be markedly enhanced when nanoparticles are employed instead of larger particles, due to a reduction in light scattering. In addition, nanoparticles of metals (e.g., gold or silver) or semiconductors (e.g., TiO₂, ZnO, or PbS) can exhibit intrinsic optical properties that may be of interest per se or in combination with the enhanced transparency caused by the nanoparticles. For such reasons, inorganic nanoparticles have found special interest in studies devoted to optical properties in composites that look back to a long history. For instance, the size-dependent color of gold nanoparticles has been used to color glass for centuries. More recently, inorganic nanoparticles were investigated with regard to optical effects in polymeric nanocomposites such as very high or very low refractive index, reversible color switching in elastomers via swelling processes, dichroism in oriented polymers, reversible photochromic behavior, or UV absorption in visually transparent materials.     

Dichroic nanocomposites based on polymers and metallic particles: from biology to materials science

Dichroic nanocomposites change their colors when they are viewed through a turning polarizer. In the case of polymer matrices containing inorganic nanoparticles, this color effect originates in anisotropic structures of inorganic moieties, such as uniaxially oriented linear assemblies of spherical nanoparticles or parallel oriented nanorods. The orientation of the particles or particle assemblies, respectively, is induced by the polymer matrix, either through oriented elongated hollow spaces or drawing. Matrices based on biopolymers (e.g. cellulose, polypeptides, chitin) as well as synthetic polymers (e.g. polyethylene, poly(vinyl alcohol)) have been employed. The dichroic colors have been generated so far mainly by silver or gold particles (including nanorods), but also other metals and occasionally also semiconductors (metalloids). Notably, dichroism is also disclosed in optical absorption spectra recorded with polarized light. Dichroism in biopolymer‐based objects with incorporated nanoparticles has been exploited for the cognition of biological fine structures, while dichroic films with technical polymers as matrices have been considered as optical switches in bicolored liquid crystal displays and authenticity cachets for documents, banknotes and packaging films. In this context, micropatterning of dichroic nanocomposites, which has been achieved by local heating procedures of materials composed of metal nanorods, is also of interest. © 2017 Society of Chemical Industry     

Gold Nanoparticle Synthesis,Morphology Control,and Stabilization Facilitated by Functional Polymers

Gold nanoparticles exhibit novel optical and catalytic properties, are nontoxic and biocompatible, and attract considerable interest in a range of applications, e.g. photonics, diagnostics, and therapeutics. The morphology (size and shape) of the nanoparticles and their surface/colloidal properties are very important in the various applications. A methodology for the synthesis in aqueous media of gold nanoparticles with controlled size and shape and exceptional colloidal stability is reviewed. This methodology is based on designer polymers that can exhibit multiple functions on the basis of the polymer intramolecular and supramolecular organization. In addition to being water based, this methodology requires no external energy input and employs commercially available polymers, e.g., poly(ethylene oxide) containing Pluronics or Poloxamers, resulting in low cost and potential environmental benefits.     

Synthesis of Energetic Polymers by the Introduction of Energetic Groups onto Polymeric Primary and Secondary Amines

Energetic polymers have been synthesised by the introduction of picryl groups onto linear polyethylenimine and polyvinylamine. The degree of substitution was 70–97% for polyethylenimine, depending upon the molecular weight of the polymer, and around 70% for polyvinylamine. N‐Picrylation of low molecular weight, model compounds was also studied. The results illustrate the influence of molecular weight on the chemical accessibility of a reaction site and reflect the difficulty of modelling polymer modification reactions using small molecules.