Solution properties of dextran–polyacrylamide graft copolymers

Cytotoxicity of Hybrid Noble Metal-Polymer Composites

The aim of the present research was to assess the cytotoxicity of gold and silver nanoparticles synthesized into dextran-graft-polyacrylamide (D-PAA) polymer nanocarrier, which were used as a basis for further preparation of multicomponent nanocomposites revealed high efficacy for antitumor therapy. The evaluation of the influence of Me-polymer systems on the viability and metabolic activity of fibroblasts and eryptosis elucidating the mechanisms of the proeryptotic effects has been done in the current research. The nanocomposites investigated in this study did not reduce the survival of fibroblasts even at the highest used concentration. Our findings suggest that hybrid Ag/D-PAA composite activated eryptosis via ROS- and Ca2+-mediated pathways at the low concentration, in contrast to other studied materials. Thus, the cytotoxicity of Ag/D-PAA composite against erythrocytes was more pronounced compared with D-PAA and hybrid Au/polymer composite. Eryptosis is a more sensitive tool for assessing the biocompatibility of nanomaterials compared with fibroblast viability assays.

Efficient Retention and Alpha Spectroscopy of Actinides from Aqueous Solutions Using a Combination of Water-Soluble Star-like Polymers and Ultrafiltration Membranes

We explored two approaches to recover uranium and plutonium from aqueous solutions at pH 4 and pH 7 using water-soluble star-like polyacrylamide polymers with a dextran core. In the first approach, a solution comprising a neutral or ionomer polymer was mixed with a radionuclide solution to form polymer–metal complexes that were then retained by ultrafiltration (UF) membranes under applied pressure. The same polymers were first deposited on the membrane in the second approach using pressure-driven flow. The applied polymers had an overall diameter of gyration of 120 nm, which exceeded the nominal diameter of the UF membrane pores. The polymers showed a high affinity to uranyl but could also be used to extract Pu from neutral or near-neutral pH solutions. Direct-flow single-step filtration and alpha spectrometry demonstrated that the UF membranes containing star-like copolymers could recover 99% of U and up to 60% of Pu from deionized water after filtering 15 mL solutions containing 25 ppm and 33 ppb of the actinides, correspondingly. The sorption capacity of the polymers for uranium could be measured as 1mg U per mg of the polymer after six subsequent filtration steps. Alpha spectroscopy of the deposited actinides revealed peculiarities of the structural organization of polymers and their complexes with U or Pu, depending on the approach. Though both approaches were efficient, the second approach (deposition of the polymer on the membrane followed by filtration) has an additional advantage of protecting the membrane pores from capillary collapse by filling them with the polymer chains. Therefore, these polymer-modified membranes could be used either in continuous or multi-step filtration process with drying after each step without deterioration of their sorption characteristics.

Cefuroxime-Loaded Hydrogels for Prevention and Treatment of Bacterial Contamination of Open Wounds

Dextran/Sulfodextran-graft-polyacrylamide- and polyacrylamide-based hydrogels were synthesized by radical polymerization and loaded with cefuroxime to obtain antimicrobial wound dressings. Antibiotic release from the antibiotic-loaded hydrogels into an aqueous solution was studied by the HPLC-UV method. It is shown that cefuroxime-loaded Dextran/Sulfodextran-graft-polyacrylamide hydrogels release the antibiotic more slowly compared to polyacrylamide hydrogel with the same density of cross-links. Antibacterial activity of the synthesized materials was tested in vitro against wild strains of S. aureus, E. coli, and Klebsiella spp. The possibility of using the obtained antimicrobial hydrogels for the treatment of infected wounds was confirmed in vivo in a rat model.

Characterization of Hydrophobically Modified Polyacrylamide in Mixed Polymer-Gemini Surfactant Systems for Enhanced Oil Recovery Application

The study deals with the synthesis and characterization of the hydrophobically modified polyacrylamide (HMPA) copolymer and its functional property evaluation in mixed polymer-gemini surfactant systems for application in enhanced oil recovery (EOR). The copolymer was initially prepared in the laboratory using acrylamide and N-phenylacrylamide monomer units via an addition polymerization route. The synthesized copolymer was characterized by Fourier transform infrared and proton nuclear magnetic resonance to identify suitable functional groups in the compound. Gel permeation chromatography tests showed that the polymer has a molecular weight of 2.098 × 10⁵ Da. Copolymer solution showed favorable tolerance to variations in temperature and salinity. Salt precipitation studies identified tolerance limit up to 25% NaCl at a temperature of 343 K. Viscosity of HMPA fluids showed an increase with increasing concentration. Interestingly, salt addition until 1.0% NaCl showed an increase in solution viscosity owing to the electrostatic shielding of the HMPA polymer and strengthened intermolecular association of the hydrophobic groups. This behavior is against physicochemical properties observed in the case of conventional polymers but exhibits promising functionality in EOR processes wherein better oil mobility control is desired under subsurface conditions. Gemini surfactants accommodate onto "vacant adsorption" sites onto the liquid surface, improving the interfacial adsorption property and reducing surface tension. In the presence of gemini surfactant polymers forming mixed nanoemulsion fluid systems with favorable pseudoplastic character, their viscosities initially increase with surfactant concentration due to binding of surfactant molecules to hydrophobic junctions of polymer chains to form mixed micelles. Eventually, polymer hydrophobes get saturated with surfactant micelles, and viscosity decreases due to electrostatic repulsion among surfactant micelles. Dynamic light scattering analyses confirmed the formation of nanoemulsion droplets with sizes of <310 nm in the case of {surfactant + copolymer} encapsulation. Zeta potential measurements showed that an increase in 14-6-14 gemini surfactant concentration enhanced the stability of nanoemulsion fluid due to increasing zeta potential values. However, the nonionic SF-6-SF surfactant does not affect the zeta potential of nanoemulsions. Surfactant addition reduced the oil-aqueous interfacial tension of polymer solutions to several magnitudes of an order of 10^-1 to 10^-2 mN/m. Contact angle studies identified the ability of the polymer as well as polymer-surfactant nanoemulsions to alter the wettability of the reservoir rock from the intermediate-wet (90°-120°) to strongly water-wet state (<20°) at different temperatures. Analyzed formulations showed favorable miscibility with crude oil at 343 K. In summary, HMPA/gemini surfactant-based emulsions possess promising physicochemical and stabilization attributes for application in EOR.

Some Properties of Chemical Cross-Linking Biohydrogel from Starch and Chitosan

Chemical cross-linking was developed to prepare starch and chitosan-based hydrogels. First, the precursor of starch was synthesized through the reaction of carboxymethylation with sodium monochloroacetate, and then chitosan was grafted by using methacrylic acid as cross-linker. In this research, sago and cassava starches were used and mixed with chitosan, and the effect of methacrylic acid concentration was investigated to determine the grafting parameters and hydrogel characteristics. Compared to native starch and carboxymethylated starch, hydrogels from both starches have high ability to swell and high capacity to absorb water and oil. The highest grafting yield, grafting efficiency, and monomer conversion were achieved by experiment using 0.550 g of methacrylic acid per g of CMS-chitosan mixture. These hydrogels have a good potency as biodegradable absorbents for pharmaceutical and industrial application.

Design and Study of a Novel Thermal-Resistant and Shear-Stable Amphoteric Polyacrylamide in High-Salinity Solution

Abstract: Water-soluble polymers are widely used in oilfields. The rheological behaviors of these polymers in high-salinity solution are very important for stimulation of high-salinity reservoirs. In this work, a novel thermal-resistant and shear-stable amphoteric polyacrylamide (PASD), prepared from acrylamide (AM), sodium styrene sulfonate (SSS), and acryloxyethyl trimethylammonium chloride (DAC) monomers, was prepared by free-radical polymerization in high-salinity solution. The amphoteric polyacrylamide was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (¹H NMR), elemental analysis, thermogravimetric analysis (TG), and scanning electron microscopy (SEM). The amphoteric polyacrylamide exhibited excellent salinity tolerance. The slow increase in apparent viscosity of the polymer with increase in salinity was interesting. The amphoteric polyacrylamide showed perfect temperature resistance in high-salinity solution. The viscosity retention reached 38.9% at 120 °C and was restored to 87.8% of its initial viscosity when temperature was decreased to room temperature. The retention ratio of apparent viscosity reached 49.7% at 170 s^-1 and could still retain it at 25.8% at 1000 s^-1. All these results demonstrated that PASD had excellent thermal-resistance and shear-stability in high-salinity solution. We expect that this work could provide a new strategy to design polymers with excellent salinity-tolerance, thermal-resistance, and shear-stability performances.

Self-Assembly Assisted Fabrication of Dextran-Based Nanohydrogels with Reduction-Cleavable Junctions for Applications as Efficient Drug Delivery Systems

In order to overcome the key challenge in improving both fabrication efficiency and their drug delivery capability of anti-cancer drug delivery systems (ACDDS), here polyacrylic acid (PAA) grafted dextran (Dex) nanohydrogels (NGs) with covalent crosslinked structure bearing redox sensitive disulfide crosslinking junctions (Dex-SS-PAA) were synthesized efficiently through a one-step self-assembly assisted methodology (SAA). The Dex-SS-PAA were subsequently conjugated with doxorubicin through an acid-labile hydrazone bond (Dex-SS-PAA-DOX). The in vitro drug release behavior, anti-cancer effects in vivo, and biosafety of the as-prepared acid- and redox-dual responsive biodegradable NGs were systematically investigated. The results revealed that the Dex-SS-PAA-DOX exhibited pH- and redox-controlled drug release, greatly reduced the toxicity of free DOX, while exhibiting a strong ability to inhibit the growth of MDA-MB-231 tumors. Our study demonstrated that the Dex-SS-PAA-DOX NGs are very promising candidates as ACDDS for anti-cancer therapeutics.

Dextran-Polyacrylamide as Matrices for Creation of Anticancer Nanocomposite

Drug targeting to specific organs and tissues is one of the crucial endeavors of modern pharmacotherapy. Controlled targeting at the site of action and reduced time of exposure of nontargeted tissues increase the efficacy of the treatment and reduce toxicity and side effects, improving compliance and convenience. Nanocarriers based on the branched copolymers dextran-graft-polyacrylamide were synthesized and characterized and were tested on phagocytic cells. It was shown that these nanoparticles are actively captured by phagocytic cells and that they are not cytotoxic. The polymer nanoparticles loaded with cisplatin at different concentrations from 0.1 to 10 μg/mL yielded dose-dependent decrease in viability of chronic myelogenous leukemia and histiocytic lymphoma cells. The lowest percentage of viable cells was observed for lymphoma cells (22%). Taking into account the fact that our nanoparticles will act mainly on malignant phagocytic cells and do not affect healthy cells, they can thus potentially be used for the therapeutic treatment of tumor cells having phagocytic activity. The effect of nanosilver on cell viability was lower than the one of polymer/cisplatin composite. The data from the cytotoxic studies indicate that nanosilver induces toxicity in cells. However, when the copolymers were conjugated to both nanosilver and cisplatin, such a nanosystem displayed less cytotoxic effect compared to the conjugates of dextran-polyacrylamide and cisplatin.

SAXS Combined with UV-vis Spectroscopy and QELS: Accurate Characterization of Silver Sols Synthesized in Polymer Matrices

The present work demonstrates a validation of small-angle X-ray scattering (SAXS) combining with ultra violet and visible (UV-vis) spectroscopy and quasi-elastic light scattering (QELS) analysis for characterization of silver sols synthesized in polymer matrices. Polymer matrix internal structure and polymer chemical nature actually controlled the sol size characteristics. It was shown that for precise analysis of nanoparticle size distribution these techniques should be used simultaneously. All applied methods were in good agreement for the characterization of size distribution of small particles (less than 60 nm) in the sols. Some deviations of the theoretical curves from the experimental ones were observed. The most probable cause is that nanoparticles were not entirely spherical in form.

Synthesis, characterization and cyclic voltammetric study of copper(II) and nickel(II) polymer chelates

Graft copolymers based on dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) were synthesized by free radical initiated solution polymerization technique using ceric ammonium nitrate as initiator. These graft copolymers were used to prepare Cu(II) and Ni(II) chelates by reactions with Cu(II) and Ni(II) metal ions respectively. Graft copolymer and metal chelates were characterized by elemental analysis, intrinsic viscosity, FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Elemental analysis, intrinsic viscosity and FT-IR studies revealed the incorporation of metal ions to form metal chelates. SEM studies showed the change in morphology due to metal incorporation. From AFM studies it was observed that there was increase in Root mean square (RMS) roughness values in case of metal complexes. Metal chelates were observed to be thermally more stable than graft copolymer from TGA. UV-vis spectroscopy study revealed increase in absorbance values and cyclic voltammetric (CV) studies showed more than tenfold increase in redox current due to formation of Cu(II) and Ni(II) metal chelates. The binding constants of each complex determined by using UV-visible spectroscopy revealed that Cu(II) has more binding ability than Ni(II).

In situ formation of silver nanoparticles in linear and branched polyelectrolyte matrices using various reducing agents

Silver nanoparticles were synthesized in linear and branched polyelectrolyte matrices using different reductants and distinct synthesis conditions. The effect of the host hydrolyzed linear polyacrylamide and star-like copolymers dextran-graft-polyacrylamide of various compactness, the nature of the reductant, and temperature were studied on in situ synthesis of silver sols. The related nanosystems were analyzed by high-resolution transmission electron microscopy and UV-vis absorption spectrophotometry. It was established that the internal structure of the polymer matrix as well as the nature of the reductant determines the process of the silver nanoparticle formation. Specifically, the branched polymer matrices were much more efficient than the linear ones for stable nanosystem preparation.

Light Scattering and Viscosimetry Study of Star-Like Dextran-Graft-Polyacrylamide

Dextran-graft-Polyacrylamide copolymers (D-g-PAA) with a polysaccharide backbone having different molecular weights (Mw = 20 000 and Mw = 70 000) and with various number of PAA-grafts per one Dextran macromolecule have been synthesized. Light scattering and viscometry investigations have shown that the internal structure of D-g-PAA copolymers depends upon the distance between PAA-grafts. Compactness of D20-g-PAA copolymers is lower in comparison with D70-g-PAA samples due to different conformations of PAA grafted chains: a “mushroom” conformation for D70-g-PAA and a “worm-like” one for D20-g-PAA samples.