Polyelectrolyte Research Articles

Poly(pentahydropyrimidine)‐Based Hybrid Hydrogel with Synergistic Antibacterial and Pro‐Angiogenic Ability for the Therapy of Diabetic Foot Ulcers

AbstractBacterial infection and impaired angiogenesis make the treatment of diabetic foot ulcers (DFU) extremely challenging. Cationic polymers are expected to treat infected wounds due to their excellent antibacterial properties, but still, it is difficult to meet the therapeutic needs of pro‐angiogenesis and anti‐infections due to their simple construction units and outmoded synthesis methods. Herein, a cationic poly(pentahydropyrimidine) (PPHP) library with strong modifiability is synthesized to construct a hybrid hydrogel with synergistic therapeutic effects for the treatment of infected DFUs. It is found that the as‐synthesized hybrid hydrogel can up‐regulate angiogenesis‐related gene (HIF‐1, VEGF, and bFGFR/bFGF) expression and targeted disruption of bacterial cell membranes, which finally promotes the healing of infected DFU (wound healing rate: 92%) within 10 days. This hydrogel, thus, holds great promise in developing new strategies to significantly enhance the treatment of DFU and other bacterial‐infected pathological diagnoses.

Polyelectrolyte Cylindrical Brushes in Hairy Gels.

We considered dispersions of cylindrical polyelectrolyte (PE) brushes with stiff backbones, and polymer-decorated nanorods with tunable solubility of the brush-forming PE chains that affected thermodynamic stability of the dispersions. We focused on thermo-induced and deionization-induced conformational transition that provokes loss of aggregative dispersion stability of nanorods decorated with weakly ionized polyions. A comparison between theoretical predictions and experiments enabled rationalization and semi-quantitative interpretation of the experimental results.

Poly(2-oxazoline)-Based Polyplexes as a PEG-Free Plasmid DNA Delivery Platform.

The present study expands the versatility of cationic poly(2-oxazoline) (POx) copolymers as a polyethylene glycol (PEG)-free platform for gene delivery to immune cells, such as monocytes and macrophages. Several block copolymers are developed by varying nonionic hydrophilic blocks (poly(2-methyl-2-oxazoline) (pMeOx) or poly(2-ethyl-2-oxazoline) (pEtOx), cationic blocks, and an optional hydrophobic block (poly(2-isopropyl-2-oxazoline) (iPrOx). The cationic blocks are produced by side chain modification of 2-methoxy-carboxyethyl-2-oxazoline (MestOx) block precursor with diethylenetriamine (DET) or tris(2-aminoethyl)amine (TREN). For the attachment of a targeting ligand, mannose, azide-alkyne cycloaddition click chemistry methods are employed. Of the two cationic side chains, polyplexes made with DET-containing copolymers transfect macrophages significantly better than those made with TREN-based copolymer. Likewise, nontargeted pEtOx-based diblock copolymer is more active in cell transfection than pMeOx-based copolymer. The triblock copolymer with hydrophobic block iPrOx performs poorly compared to the diblock copolymer which lacks this additional block. Surprisingly, attachment of a mannose ligand to either copolymer is inhibitory for transfection. Despite similarities in size and design, mannosylated polyplexes result in lower cell internalization compared to nonmannosylated polyplexes. Thus, PEG-free, nontargeted DET-, and pEtOx-based diblock copolymer outperforms other studied structures in the transfection of macrophages and displays transfection levels comparable to GeneJuice, a commercial nonlipid transfection reagent.

Effect of Organic Functional Groups on Poly(ethylene oxide) Electrolytes for High-Performance Solid-State Lithium-Metal Batteries

Effect of Organic Functional Groups on Poly(ethylene oxide) Electrolytes for High-Performance Solid-State Lithium-Metal Batteries

Parametric study of the silver nanoparticles deposition on polyelectrolyte supporting layers

Colloidal nanoparticles deposition on polyelectrolyte (PE) supporting layers is a widespread technique to achieve high density nanoparticle coatings, however the choice of the parameters is often not consistent and varies in different reports. Frequently the obtained films suffer from the aggregation and non-reproducibility. Here, we addressed the main variables in silver nanoparticles deposition—the immobilization time; concentration of the PE in the solution; the thickness of PE underlayer and overlayer; the concentration of salt in the PE solution during the formation of a underlayer. We report on the formation of the high-density silver nanoparticle films and ways to tune their optical density in the wide range using the immobilization time as well as the thickness of PE overlayer. Silver colloidal films with maximum reproducibility were obtained by adsorption of nanoparticles on 1 underlayer of 5 g l−1 polydiallyldimethylammonium chloride with 0.5 M NaCl concentration. The results are promising for the fabrication of the reproducible colloidal silver films for multiple applications, such as plasmon enhanced fluorescent immunoassays and surface enhanced Raman scattering sensors.

Impacts of non-microbial soils on polychloramide disinfectants

The presence of some nonmicrobial chemicals and surfaces, herein called “soils”, are known to degrade the performance of biocides, and biocidal assays often include mixtures of materials to mimic the effects of soils. We hypothesized that water-soluble anionic polychloramide biocides were less sensitive to soil interference than cationic polymeric biocides. The relationships between soil composition and antimicrobial polymer biocidal activity were compared for an anionic polychloramide, a cationic polychloramide, and a cationic poly(quaternary ammonium) biocide. The nanoscale soil models individually investigated were polyacrylic acid (PAA), cellulose nanocrystals (CNCs), and bovine serum albumin. The low molecular weight model soils were ammonium chloride, glycine, and succinimide. Three types of soil impacts were identified: 1) sequestration, whereby the soil physically inhibited transport of the biocide to microbes; 2) extraction, whereby the soil reduced or extracted oxidative chlorine, decreasing or eliminating the oxidative chlorine strength; and 3) extraction whereby the biocidal activity increases in the presence of a low molecular weight chemical that carries oxidative Cl from the polymer to the microbes. PAA and CNCs inhibit cationic biocides by sequestration but have little impact on anionic polychloramide. Glycine and BSA extract oxidative chlorine, lowering the biocidal activity of the anionic and cationic polychloramides while not impacting the poly(quaternary ammonium) biocide. Finally, the presence of succinimide increased bacteria deactivation of both anionic and cationic polychloramides. We propose that succinimide extracts oxidative chlorine from the polychloramides and transports it to the bacteria.

Enhanced catalytic nitrophenol reduction via highly porous hollow silica nanospheres stabilized Au nanoclusters

In this work, we report the synthesis of Au nanoparticles encaged in hollow porous silica nanospheres (Au@HPSNs), which features extremely small Au nanoclusters (∼1.3 nm) encapsulated in high specific surface area (∼800 m2/g) HPSNs. We used the electrostatic attraction between the anions of poly(acrylic acid) (PAA) and protonated poly(ethylenimine) (PEI) to build the micelles system in an ethanol–water system, which was employed as the templates for deposition of silica to give the core–shell structured PEI-PAA@SiO2. The final materials Au@HPSNs were obtained by soaking PEI-PAA@SiO2 in HAuCl4 solution and subsequent calcination. The Au@HPSNs show extremely high catalytic efficiency for 4-nitrophenol (4-NP) reduction with NaBH4, and exhibit the highest heterogeneous Au-based catalytic efficiency up to date for 4-NP reduction. The greatly enhanced performance of Au@HPSNs could be ascribed to ultra-fine Au nanoclusters and the small mass transfer hindrance with high specific surface area hollow porous silica.

Surface Modification Determines the Distribution and Toxicity of Quantum Dots during the Development of Early Staged Zebrafish.

Surface modifications are generally used to functionalize QDots to improve their properties for practical applications, but the relationship between QDot modification and biological activity is not well understood. Using an early staged zebrafish model, we investigated the biodistribution and toxicity of CdSe/ZnS QDots with four types of modifications, including anionic poly(ethylene glycol)-carboxyl ((PEG)n-COOH), anionic mercaptopropionic acid (MPA), zwitterionic glutathione (GSH), and cationic cysteamine (CA). None of the QDots showed obvious toxicity to zebrafish embryos prior to hatching because the zebrafish chorion is an effective barrier that protects against QDot exposure. The QDots were mainly absorbed on the epidermis of the target organs after hatching and were primarily deposited in the mouth and gastrointestinal tract when the zebrafish started feeding. CA-QDots possessed the highest adsorption capacity; however, (PEG)n-COOH-QDots showed the most severe toxicity to zebrafish, as determined by mortality, hatching rate, heartbeat, and malformation assessments. It shows that the toxicity of the QDots is mainly attributed to ROS generation rather than Cd2+ release. This study provides a comprehensive understanding of the environmental and ecological risks of nanoparticles in relation to their surface modification.

Preparation of aldehyde-graphene quantum dots from glucose for controlled release of anticancer drug

In this study, we prepared graphene quantum dots (GQDs) via a green process using rice straw as a carbon source. The non-toxic nature of GQDs is suitable for application in human body-related research. Furthermore, GQDs possess biodegradability and biocompatibility characteristics, indicating high suitability for applications in the field of drug delivery. Based on the fact that acid-sensitive bonds between GQDs and the drug doxorubicin are formed by aldehyde groups on GQD surfaces, we adopted a semi-modified TEMPO method to partially oxidize the surface functional groups of GQDs without destroying the structure. This enabled an increase in the surface aldehyde group content, which in turn enhanced the drug loading capacity of GQDs. The aldehyde group content of the GQDs was measured via Fourier transform infrared (FTIR) spectroscopy, titration based on the Cannizzaro reaction, and X-ray photoelectron spectroscopy (XPS). The drug loading effect of the GQDs was determined via absorbance measurements at 485 nm on a UV-Vis spectrophotometer. The results indicated that the semi-modified TEMPO method significantly affected the introduction of surface aldehyde groups and the enhancement of the drug loading efficiency in GQDs. Finally, the polymeric material cationic poly (vinylcyclohexene carbonates) (CPVCHCs) was used for the encapsulation of GQDs and regulation of drug release. Under the premise that the total amount of drugs released remains unaffected, the initial burst release of the drug is effectively delayed, which aids in reducing harmful effects of the drug on the human body.

Antifouling and Water Flux Enhancement in Polyethersulfone Ultrafiltration Membranes by Incorporating Water-Soluble Cationic Polymer of Poly [2-(Dimethyl amino) ethyl Methacrylate

Novel ultrafiltration (UF) polymer membranes were prepared to enhance the antifouling features and filtration performance. Several ultrafiltration polymer membranes were prepared by incorporating different concentrations of water-soluble cationic poly [2-(dimethyl amino) ethyl methacrylate] (PDMAEMA) into a homogenous casting solution of polyethersulfone (PES). After adding PDMAEMA, the effects on morphology, hydrophilicity, thermal stability, mechanical strength, antifouling characteristics, and filtration performance of these altered blended membranes were investigated. It was observed that increasing the quantity of PDMAEMA in PES membranes in turn enhanced surface energy, hydrophilicity, and porosity of the membranes. These new modified PES membranes, after the addition of PDMAEMA, showed better filtration performance by having increased water flux and a higher flux recovery ratio (FRR%) when compared with neat PES membranes. For the PES/PDMAEMA membrane, pure water flux with 3.0 wt.% PDMAEMA and 0.2 MPa pressure was observed as (330.39 L·m-2·h-1), which is much higher than that of the neat PES membrane with the value of (163.158 L·m-2·h-1) under the same conditions. Furthermore, the inclusion of PDMAEMA enhanced the antifouling capabilities of PES membranes. The total fouling ratio (TFR) of the fabricated PES/PDMAEMA membranes with 3.0 wt.% PDMAEMA at 0.2 MPa applied pressure was 36 percent, compared to 64.9 percent for PES membranes.

Desalination performance of fabric-structured charged mosaic membrane prepared from poly(vinyl alcohol)-based charged fibers

Charged mosaic (CM) membranes were prepared from fabric structures using two types of poly(vinyl alcohol) (PVA)-based fibers. The fibers were fabricated using anionic and cationic block-type PVA, poly(vinyl alcohol-b-sodium styrene sulfonic acid), and poly(vinyl alcohol-b-vinylbenzyl trimethylammonium chloride). The fabrics were heat pressed to form a nonporous film and crosslinked with glutaraldehyde (GA) to produce fabric-structured CM membranes. Volume flux experiments indicated that the CM membrane exhibited negative osmosis, whereas the uncharged PVA membrane showed positive osmosis. The CM membrane made from the fabric exhibited sufficient mechanical strength for performing a piezodialysis experiment under a pressure of 0.3 MPa. The analytical results of piezodialysis experiments for the CM membrane indicated that the salt flux increased, whereas the water flux remained constant with an increasing initial NaCl concentration. Therefore, the salt-to-water flux ratio increased with increasing NaCl concentration. The CM membrane was desalinated with up to 1500 ppm of NaCl at a pressure of 0.3 MPa. Consequently, the fabricated CM membranes demonstrated the potential for desalinating low-salinity solutions.

Increased Nitrogenase Activity in Solar‐Driven Biohybrids Containing Non‐photosynthetic Bacteria and Conducting Polymers

AbstractA conductive polymer‐based photosynthetic biohybrid is constructed to enhance biological nitrogen fixation by increasing nitrogenase activity in the non‐photosynthetic bacterium Azotobacter Chroococcum (A. Chroococcum). The light‐harvesting cationic poly(fluorene‐alt‐phenylene) (PFP) electrostatically binds to the surface of the bacteria and possesses satisfactory conductivity to facilitate electron transfer to the bacterium, promoting the nitrogen fixation pathway through redox proteins on the surface of the bacteria when under illumination. Therefore, the nitrogenase activity, hydrogen, NH4+‐N and L‐amino acids production are increased by 260 %, 37 %, 44 %, and 47 %, respectively. The expression levels of nifD and nifK encoding molybdenum‐iron (MoFe) protein and relevant nitrogen‐fixing proteins are up‐regulated. These photoactive conductive polymer‐bacteria biohybrids provide a new method for improving the biological nitrogen fixation capability of non‐photosynthetic nitrogen‐fixing bacteria.

Increased Nitrogenase Activity in Solar-Driven Biohybrids Containing Non-photosynthetic Bacteria and Conducting Polymers.

A conductive polymer-based photosynthetic biohybrid is constructed to enhance biological nitrogen fixation by increasing nitrogenase activity in the non-photosynthetic bacterium Azotobacter Chroococcum (A. Chroococcum). The light-harvesting cationic poly(fluorene-alt-phenylene) (PFP) electrostatically binds to the surface of the bacteria and possesses satisfactory conductivity to facilitate electron transfer to the bacterium, promoting the nitrogen fixation pathway through redox proteins on the surface of the bacteria when under illumination. Therefore, the nitrogenase activity, hydrogen, NH4 + -N and L-amino acids production are increased by 260 %, 37 %, 44 %, and 47 %, respectively. The expression levels of nifD and nifK encoding molybdenum-iron (MoFe) protein and relevant nitrogen-fixing proteins are up-regulated. These photoactive conductive polymer-bacteria biohybrids provide a new method for improving the biological nitrogen fixation capability of non-photosynthetic nitrogen-fixing bacteria.

MXene-based gold nanoparticle catalyst with high activity and stability for 4-nitrophenol reduction

Catalytic reduction is considered an effective method for converting organic compounds. However, a lack of efficient catalysts has hindered its practical application. Herein, the cationic poly(diallyldimethylammonium chloride) (PDDA) was used as a stabilizer to synthesize a novel MXene-supported gold nanoparticles composite by electrostatic interaction and self-reduction methods. As a stabilizer bridging transition metal carbides (MXene, Ti3C2Tx) and gold nanoparticles (AuNPs), the PDDA polymer provided rich binding sites for AuNPs immobilization, resulting in uniform distribution of AuNPs on MXene nanosheet and efficient control over their particle size. The synergistic effects of the composite catalyst improved its catalytic activity towards 4-nitrophenol (4-NP) reduction, and the normalized rate constant (K) was high up to 2.65 × 10−2 s−1. Notably, the composite catalyst also showed high stability due to the protection of PDDA, and the conversion efficiency for 4-NP was high up to 94.85% after five recycles. Our findings presented here not only are potential for catalytic applications, but also provide a foundation for the development of efficient MXene-based catalysts.

Imaging Heterogeneous 3D Dynamics of Individual Solutes in a Polyelectrolyte Brush.

Understanding molecular transport in polyelectrolyte brushes (PEBs) is crucial for applications such as separations, drug delivery, anti-fouling, and biosensors, where structural features of the polymer control intermolecular interactions. The complex structure and local heterogeneity of PEBs, while theoretically predicted, are not easily accessed with conventional experimental methods. In this work, we use 3D single-molecule tracking to understand transport behavior within a cationic poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA) brush using an anionic dye, Alexa Fluor 546, as the probe. The analysis is done by a parallelized, unbiased 3D tracking algorithm. Our results explicitly demonstrate that spatial heterogeneity within the brush manifests as heterogeneity of single-molecule displacements. Two distinct populations of probe motion are identified, with anticorrelated axial and lateral transport confinement, which we believe to correspond to intra- vs inter-chain probe motion.

Translocation of Hydrophobic Polyelectrolytes under Electrical Field: Molecular Dynamics Study.

We studied the translocation of polyelectrolyte (PE) chains driven by an electric field through a pore by means of molecular dynamics simulations of a coarse-grained HP model mimicking high salt conditions. Charged monomers were considered as polar (P) and neutral monomers as hydrophobic (H). We considered PE sequences that had equally spaced charges along the hydrophobic backbone. Hydrophobic PEs were in the globular form in which H-type and P-type monomers were partially segregated and they unfolded in order to translocate through the narrow channel under the electric field. We provided a quantitative comprehensive study of the interplay between translocation through a realistic pore and globule unraveling. By means of molecular dynamics simulations, incorporating realistic force fields inside the channel, we investigated the translocation dynamics of PEs at various solvent conditions. Starting from the captured conformations, we obtained distributions of waiting times and drift times at various solvent conditions. The shortest translocation time was observed for the slightly poor solvent. The minimum was rather shallow, and the translocation time was almost constant for medium hydrophobicity. The dynamics were controlled not only by the friction of the channel, but also by the internal friction related to the uncoiling of the heterogeneous globule. The latter can be rationalized by slow monomer relaxation in the dense phase. The results were compared with those from a simplified Fokker-Planck equation for the position of the head monomer.

Changes in Glioblastoma Cell Characteristics by a Strong Anionic Poly(Cresolsulfonic Acid) and a Cationic Pyrvinium Complex

가장 악성 뇌종양인 교모세포종 치료제를 개발하기 위해 강력한 음이온성 고분자인 폴리(크레졸술폰산)와 양이온성 피르비늄에 대한 기초 세포 연구가 진행됐다. 이러한 혼합 약물의 최적 농도를 결정하기 위해 세포 형태 변화와 생존율에 대한 실험을 수행하고, 약물의 재투여를 통해 세포 저항성을 실험하였다. 면역화학적 검사를 통해 세포 형태학적 변화와 증식 억제 메커니즘을 유추할 수 있었으며, 테모졸로마이드와 병용할 경우 혼합물이 더 큰 세포독성 효과를 보였다. 치료약으로 개발할 수 있는 가능성과 함께 메커니즘, 세포 반응 및 동물 실험에 대한 추가 연구가 필요하다.

Polymer complexation: Partially ionizable asymmetric polyelectrolytes.

Theories of bulk coacervation of oppositely charged polyelectrolytes (PE) obscure single molecule level thermodynamic details, considered significant for coacervate equilibrium, whereas simulations account for only pairwise Coulomb interaction. Also, studies of effects of asymmetry on PE complexation are rare compared to symmetric PEs. We develop a theoretical model, accounting for all entropic and enthalpic contributions at the molecular level, and the mutual segmental screened Coulomb and excluded volume interactions between two asymmetric PEs, by constructing a Hamiltonian following Edwards and Muthukumar. Assuming maximal ion-pairing in the complex, the system free energy comprising configurational entropy of the polyions and free-ion entropy of the small ions is minimized. The effective charge and size of the complex, larger than sub-Gaussian globules as for symmetric chains, increase with asymmetry in polyion length and charge density. The thermodynamic drive for complexation is found to increase with ionizability of symmetric polyions and with a decrease in asymmetry in length for equally ionizable polyions. The crossover Coulomb strength demarcating the ion-pair enthalpy-driven (low strength) and counterion release entropy-driven (high strength) is marginally dependent on the charge density, because so is the degree of counterion condensation, and strongly dependent on the dielectric environment and salt. The key results match the trends in simulations. The framework may provide a direct way to calculate thermodynamic dependencies of complexation on experimental parameters such as electrostatic strength and salt, thus to better analyze and predict observed phenomena for different sets of polymer pairs.

Force Regulation by Sequence-Defined Polyelectrolytes

In order to achieve multifunctional adhesive materials with water and salt tolerance, it is crucial to understand the electrostatic mechanism of nanoconfined polyelectrolytes (PEs) with specific monomer sequences. Here, using density functional theory (DFT), self-consistent field theory (SCFT), and molecular dynamics (MD) simulation, we analyzed the microstructures of sequence-defined PEs confined in a nanoscale slit and the relationship between sequences and the attractive forces induced by the nanoconfined PEs. Among three sequence-defined (alternating [A], tapered [T], and reversely tapered [R] sequence) PEs, due to the formation of stable multibridge conformations, [A]-sequence PEs induce the strongest attractive forces even in the case with high salt concentrations, i.e., the best salt tolerance. It is worth emphasizing that salt enhancement of attractive forces occurs in systems with [A]-sequence PEs due to the screening of repulsive interactions between PE chains. In contrast, in systems with [T]-sequence PEs, the shielding of the attractive interactions between surfaces and charged monomers significantly attenuates the attractive forces between surfaces at high salt concentrations. In addition, the strength of attractive forces can be regulated by block number Nb. At high charge fractions such as fc = 0.5, the attractive forces induced by [A]-sequence PEs become stronger with Nb, while at low charge fractions such as fc = 0.2, the attractive forces vary nonmonotonically with Nb due to the electrostatic correlations.

Modification Approaches of Polyphenylene Oxide Membranes to Enhance Nanofiltration Performance.

Presently, water pollution poses a serious threat to the environment; the removal of organic pollutants from resources, especially dyes, is very important. Nanofiltration (NF) is a promising membrane method to carry out this task. In the present work, advanced supported poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membranes were developed for NF of anionic dyes using bulk (the introduction of graphene oxide (GO) into the polymer matrix) and surface (the deposition of polyelectrolyte (PEL) layers by layer-by-layer (LbL) technique) modifications. The effect of PEL combinations (polydiallyldimethylammonium chloride/polyacrylic acid (PAA), polyethyleneimine (PEI)/PAA, and polyallylamine hydrochloride/PAA) and the number of PEL bilayers deposited by LbL method on properties of PPO-based membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Membranes were evaluated in NF of food dye solutions in ethanol (Sunset yellow (SY), Congo red (CR), and Alphazurine (AZ)). The supported PPO membrane, modified with 0.7 wt.% GO and three PEI/PAA bilayers, exhibited optimal transport characteristics: ethanol, SY, CR, and AZ solutions permeability of 0.58, 0.57, 0.50, and 0.44 kg/(m2h atm), respectively, with a high level of rejection coefficients-58% for SY, 63% for CR, and 58% for AZ. It was shown that the combined use of bulk and surface modifications significantly improved the characteristics of the PPO membrane in NF of dyes.