Protein resistance of dextran and dextran-poly(ethylene glycol) copolymer films

The protein resistance of dextran and dextran-poly(ethylene glycol) (PEG) copolymer films was examined on an organosilica particle-based assay support. Comb-branched dextran-PEG copolymer films were synthesized in a two step process using the organosilica particle as a solid synthetic support. Particles modified with increasing amounts (0.1-1.2 mg m(-2)) of three molecular weights (10,000, 66,900, 400,000 g mol(-1)) of dextran were found to form relatively poor protein-resistant films compared to dextran-PEG copolymers and previously studied PEG films. The efficacy of the antifouling polymer films was found to be dependent on the grafted amount and its composition, with PEG layers being the most efficient, followed by dextran-PEG copolymers, and dextran alone being the least efficient. Immunoglobulin gamma (IgG) adsorption decreased from ～5 to 0.5 mg m(-2) with increasing amounts of grafted dextran, but bovine serum albumin (BSA) adsorption increased above monolayer coverage (～2 mg m(-2)) indicating ternary adsorption of the smaller protein within the dextran layer.     

Biosynthesis of poly(3-hydroxybutyrate) copolymers by Azotobacter chroococcum 7B: A precursor feeding strategy

A precursor feeding strategy for effective biopolymer producer strain Azotobacter chroococcum 7B was used to synthesize various poly(3-hydroxybutyrate) (PHB) copolymers. We performed experiments on biosynthesis of PHB copolymers by A. chroococcum 7B using various precursors: sucrose as the primary carbon source, various carboxylic acids and ethylene glycol (EG) derivatives [diethylene glycol (DEG), triethylene glycol (TEG), poly(ethylene glycol) (PEG) 300, PEG 400, PEG 1000] as additional carbon sources. We analyzed strain growth parameters including biomass and polymer yields as well as molecular weight and monomer composition of produced copolymers. We demonstrated that A. chroococcum 7B was able to synthesize copolymers using carboxylic acids with the length less than linear 6C, including poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) (PHB-4MHV) using Y-shaped 6C 3-methylvaleric acid as precursor as well as EG-containing copolymers: PHB–DEG, PHB–TEG, PHB–PEG, and PHB–HV–PEG copolymers using short-chain PEGs (with n?≤?9) as precursors. It was shown that use of the additional carbon sources caused inhibition of cell growth, decrease in polymer yields, fall in polymer molecular weight, decrease in 3-hydroxyvalerate content in produced PHB–HV–PEG copolymer, and change in bacterial cells morphology that were depended on the nature of the precursors (carboxylic acids or EG derivatives) and the timing of its addition to the growth medium.     

Particle-by-particle quantification of protein adsorption onto poly(ethylene glycol) grafted surfaces

The use and advantage of flow cytometry as a particle-by-particle, low sampling volume, high-throughput screening technique for quantitatively examining the non-specific adsorption of proteins onto surfaces is presented. The adsorption of three proteins: bovine serum albumin (BSA), immunoglobulin gamma (IgG) and protein G, incubated at room temperature for 2 h onto organosilica particles modified with poly(ethylene glycol) (PEG) of increasing MW (2000, 3400, 6000, 10,000 and 20,000 g mol(-1)) and grafted amounts (0.14-1.4 mg m(-2)) was investigated as a model system. Each protein exhibited Langmuir-like, high affinity monolayer limited adsorption on unmodified particles with the proteins reaching surface saturation at 1.8, 4.0 and 2.5 mg m(-2) for BSA, IgG and protein G, respectively. Protein adsorption on PEG-modified surfaces was found to decrease with increasing amounts of grafted polymer. PEG grafting amounts >0.6 mg m(-2) effectively prevented the adsorption of the larger two proteins (BSA and IgG) while a PEG grafting amount >1.3 mg m(-2) was required to prevent the adsorption of the smaller protein G.     

RGD-grafted poly-L-lysine-graft-(polyethylene glycol) copolymers block non-specific protein adsorption while promoting cell adhesion

A novel class of surface-active copolymers is described, designed to protect surfaces from nonspecific protein adsorption while still inducing specific cell attachment and spreading. A graft copolymer was synthesized, containing poly-(L-lysine) (PLL) as the backbone and substrate binding and poly(ethylene glycol) (PEG) as protein adsorption-resistant pendant side chains. A fraction of the grafted PEG was pendantly functionalized by covalent conjugation to the peptide motif RGD to induce cell binding. The graft copolymer spontaneously adsorbs from dilute aqueous solution onto negatively charged surfaces. The performance of RGD-modified PLL-g-PEG copolymers was analyzed in protein adsorption and cell culture assays. These coatings efficiently blocked the adsorption of serum proteins to Nb(2)O(5) and tissue culture polystyrene while specifically supporting attachment and spreading of human dermal fibroblasts. This surface functionalization technology is expected to be valuable in both the biomaterial and biosensor fields, because different signals can easily be combined, and sterilization and application are straightforward and cost-effective.     

Separation of macromolecules by ultrafiltration: Removal of poly(ethylene glycol) from human albumin

Mixtures of albumin and poly(ethylene glycol) (PEG) were used to elucidate some of the factors which influence the separation of macromolecules by thin-channel ultrafiltration. Several membranes which readily passed PEG-4000 in the absence of protein were found to exhibit increased rejection of the synthetic polymer when albumin was added to the system. Based on a comparison of filtration flux and net sieving properties, the PM-30 membrane of Amicon was chosen for further characterization. The increased rejection of PEG-4000 in the presence of albumin was independent of albumin concentration between 1 and 100 mg/ml and persisted even after albumin was removed and the system flushed with water. Overnight incubation of the membrane with trypsin restored the original sieving properties, indicating that the ‘permanent’ effects were due to irreversible adsorption to the membrane. By measuring flux over a 10⁶-fold range of albumin concentration it was possible to resolve the effects of protein adsorption, a saturable process which occurs at low protein concentration (<0.01 mg/ml), from the effects of concentration polarization which occur at high protein concentration (>0.1 mg/ml). Only the former process has an effect on the net sieving properties in this system. In spite of the adverse effects of protein adsorption, it was still possible to obtain efficient removal of PEG-4000 from albumin. Exchange of approximately 5 vols. of solvent at room temperature resulted in a 10-fold reduction in the concentration of PEG in the sample, with no loss of albumin, and no formation of albumin dimers.     

Multifunctional poly(ethylene glycol) semi-interpenetrating polymer networks as highly selective adhesive substrates for bioadhesive peptide grafting

Novel artificial extracellular matrices were synthesized in the form of semi-interpenetrating polymer networks containing copolymers of poly(ethylene glycol) and acrylic acid (PEG-co-AA) grafted with synthetic bioadhesive peptides onto exposed carboxylic acid moieties. These substrates were very resistant to cell adhesion, but when they were grafted with adhesive peptides they were highly biospecific in their ability to support cell adhesion. Extensive preadsorption of adhesive proteins or peptides did not render these materials cell adhesive; yet covalent grafting of adhesive peptides did render these materials highly cell adhesive even in the absence of serum proteins. Polymer networks containing immobilized PEG-co-AA were grafted with peptides at densities of 475 +/- 40 pmol/cm(2). Polymer networks containing immobilized PEG-co-AA N-terminally grafted with GRGDS supported cell adhesion efficiencies of 42 +/- 4% 4 h after seeding and became confluent after 12 h. These cells displayed cell spreading and cytoskeletal grafted with inactive control peptides (GRDGS, GRGES, or no peptide) supported cell adhesion efficiencies of 0 +/- 0%, even when challenged with high seeding densities (to 100,000 cell/cm(2)) over 14 days. These polymer networks are suitable substrates to investigate in vitro cell-surface interactions in the presence of serum proteins without nonspecific protein adsorption adhesion signals other than those immobilized for study.     

Marine anti-biofouling efficacy of amphiphilic poly(coacrylate) grafted PDMSe: effect of graft molecular weight

There is currently strong motivation due to ecological concerns to develop effective anti-biofouling coatings that are environmentally benign, durable, and stable for use by the maritime industry. The antifouling (AF) and fouling-release (FR) efficacy of amphiphilic, charged copolymers composed of ~52% acrylamide, ~34% acrylic acid, and ~14% methyl acrylate grafted to poly(dimethyl siloxane) (PDMSe) surfaces were tested against zoospores of the green alga Ulva linza and the diatom Navicula incerta. The biofouling response to molecular weight variation was analyzed for grafts ranging from ~100 to 1,400 kg mol^?1, The amphiphilic coatings showed a marked improvement in the FR response, with a 55% increase in the percentage removal of diatoms and increased AF efficacy, with 92% reduction in initial attachment density of zoospores, compared to PDMSe controls. However, graft molecular weight, in the range tested, was statistically insignificant. Grafting copolymers to PDMSe embossed with the Sharklet? microtopography did not produce enhanced AF efficacy.     

Aqueous polymer two-phase systems formed by new thermoseparating polymers

A set of new polymers that can be used as phase forming components in aqueous two-phase systems is presented. All polymers studied have thermoseparating properties i.e. form one separate polymer enriched phase and one aqueous solution when heated above the critical temperature. This property makes the polymers attractive alternatives to the polymers used in traditional aqueous two-phase systems such as poly(ethylene glycol) (PEG) and dextran. The thermal phase separation simplifies recycling of the polymers, thus making the aqueous two-phase systems more cost efficient and suitable for use in large scale. Thermoseparating polymers studied have been copolymers of ethylene oxide and propylene oxide (EO-PO), poly (N-isopropylacrylamide) (poly-NIPAM), poly vinyl caprolactam (poly-VCL) and copolymers of N-isopropylacrylamide and vinyl caprolactam with vinyl imidazole (poly(NIPAM-VI) and poly(VCL-VI), respectively). In addition, the copolymer poly(NIPAM-VI) has the property to be uncharged at pH above 7.0 and positively charged at lower pH. This allows the partitioning of protein to be directed by changing the pH in the system instead of the traditional addition of salt to direct the partitioning. Hydrophobically modified EO-PO copolymer (HM-(EO-PO)) with alkyl groups (C₁₄) at both ends forms two-phase system with for example poly(NIPAM-VI). The phase diagram for poly(NIPAM-VI)/HM-(EO-PO) was determined and the model proteins lysozyme and BSA were partitioned in this system. For BSA in poly(NIPAM-VI)/HM-(EO-PO) system a change in pH from 8.0 to 5.4 results in a change of partition coefficient from K=0.8 to K=5.1, i.e. BSA could be transferred from the HM-(EO-PO) phase to the poly(NIPAM-VI) phase. BSA partitioning in poly(NIPAM-VI)/HM-(EO-PO) system allows quantitative BSA recovery, and recoveries of poly(NIPAM-VI) and HM-(EO-PO) were 53% and 92%, respectively, after the thermoseparation step.     

Enhanced production of poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-4-hydroxybutyrate) copolymer with manipulated variables and its properties

Cupriavidus sp. USMAA1020, a local isolate was able to biosynthesis poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymer with various 4HB precursors as the sole carbon source. Manipulation of the culture conditions such as cell concentration, phosphate ratio and culture aeration significantly affected the synthesis of P(3HB-co-4HB) copolymer and 4HB composition. P(3HB-co-4HB) copolymer with 4HB compositions ranging from 23 to 75 mol% 4HB with various mechanical and thermal properties were successfully produced by varying the medium aeration. The physical and mechanical properties of P(3HB-co-4HB) copolymers were characterized by NMR spectroscopy, gel-permeation chromatography, tensile test, and differential scanning calorimetry. The number-average molecular weights (M _n) of copolymers ranged from 260 × 10³ to 590 × 10³Da, and the polydispersities (M _w/M _n) were between 1.8 and 3.0. Increases in the 4HB composition lowered the molecular weight of these copolymers. In addition, the increase in 4HB composition affected the randomness of copolymer, melting temperature (T _m), glass transition temperature (T _g), tensile strength, and elongation to break. Enzymatic degradation of P(3HB-co-4HB) films with an extracellular depolymerase from Ochrobactrum sp. DP5 showed that the degradation rate increased proportionally with time as the 4HB fraction increased from 17 to 50 mol% but were much lower with higher 4HB fraction. Degradation of P(3HB-co-4HB) films with lipase from Chromobacterium viscosum exhibited highest degradation rate at 75 mol% 4HB. The biocompatibility of P(3HB-co-4HB) copolymers were evaluated and these copolymers have been shown to support the growth and proliferation of fibroblast cells.     

Assessment of risk of GHG emissions from Tehri hydropower reservoir,India

The hydropower reservoirs, considered as a green source of energy, are now found to emit significant quantities of greenhouse gas (GHG) to the atmosphere. This article attempts to predict the vulnerability of Tehri reservoir, India to GHG emissions using the GHG risk assessment tool (GRAT). The GRAT is verified with experimental GHG fluxes. The annual mean CO₂ fluxes from diffusion, bubbling, and degassing were 425.93 ± 122.50, 4.81 ± 1.33, and 7.01 ± 2.77 mg m^?2d^?1, whereas CH₄ fluxes were 23.11 ± 7.08, 4.79 ± 1.08, and 7.41 ± 4.50 mg m^?2d^?1, respectively, during 2011–12. The model found that Tehri reservoir emitted higher CO₂ and CH₄ (i.e., 790 mg m^?2d^?1 and 64 mg m^?2d^?1, respectively) in 2011, which came within vulnerability range causing more climate change impact. By the year 2015, it would scale down to medium risks necessitating no further assessment of GHG. Significant difference between predicted and experimental GHG emission are assessed, which may be due to insufficient data, spatial and temporal variations, decomposition of flooded biomass, limitation of GRAT model, and inadequate methodology. The study reveals that GHG emission from Tehri reservoir is less than predicted by the GRAT.     

Equilibrium and Kinetics of Adsorption of Mn2+ by Haloarchaeon Halobacterium sp. GUSF (MTCC3265)

The coastal waters of countries bordering on an ocean show increases in manganese pollution due to runoff from mining activity and from industries dealing with production of ferroalloys, steel, iron, petrochemicals, and fertilizers. One gram of dried cells of haloarchaeon Halobacterium sp. GUSF (MTCC3265) adsorbed 99% Mn²⁺ in 60 min at pH 6.8 and 30ºC on contact with 109.54 mg Mn²⁺ per liter in saline solution. Adsorbed Mn²⁺ was quantified by atomic absorption spectrometry and demonstrated on the cell surface by SEM-EDX. Mn²⁺ adsorbed to functional groups of the adsorbent was studied by FTIR. The adsorption process of Mn²⁺ showed saturation and followed pseudo–second-order kinetics; was consistent with the homogeneity of the Langmuir model (R² of 0.99); exhibited a Q_max of 62.5 mg g^?1 and a binding energy of 0.018 L mg^?1. The Mn²⁺adsorption was also consistent with the heterogeneity of the Freundlich model by exhibiting a K_f of 1.0 mg g^?1 with an n value of 1.1. Adsorption efficiency of 99% was retained even after a third adsorption-desorption cycle. This is the first report on metal ion adsorption, using Mn²⁺ as an example, by the haloarchaeon Halobacterium sp. GUSF (MTCC3265) in the domain Archaea.     

Drug release from and hydrolytic degradation of a poly(ethylene glycol) grafted poly(3-hydroxyoctanoate)

Monoacrylate-poly(ethylene glycol)-grafted poly(3-hydroxyoctanoate) (PEGMA-g-PHO) copolymers were synthesized to develop a swelling-controlled release delivery system for ibuprofen as a model drug. The in vitro hydrolytic degradation of and the drug release from a film made of the PEGMA-g-PHO copolymer were carried out in a phosphate buffer saline (pH 7.4) medium. The hydrolytic degradation of the copolymer was strongly dependent on the degree of grafting (DG) of the PEGMA group. The degradation rate of the copolymer films in vitro increased with increasing DG of the PEGMA group on the PHO chain. The copolymer films showed a controlled delivery of ibuprofen to the medium in periods of time that depend on the composition, hydrophilic/hydrophobic characteristics, initial drug loading amount and film thickness of the graft copolymer support. The drug release rate from the grafted copolymer films was faster than the rate of weight loss of the films themselves. In particular, a combination of the low DG of the PEGMA group in the PHO chains with the low ibuprofen solubility in water led to long-term constant release from these matrices in vitro.     

A New Synthesis Of Coenzymically Active Water-Soluble Macromolecular Nad And Nadp Derivatives

Based on an unexpected transformation of N (1)-(2-aminoethyl)-NAD(P) to N⁶-(2-aminoethy1)-NAD(P) under mild aqueous conditions (pH 6.0-6.5, 50°C) synthesis of uniform macromolecular derivatives of N⁶-alkylated NAD and N⁶-alkylated NADP was possible, with, in most cases, acceptable overall yields (6-37%). The usual steps of (a) the chemical reduction with Na₂S₂O₄,(b) the Dimroth rearrangement under harsh alkaline conditions and (c) the enzymatic or chemical oxidation were omitted. This represents a significant simplification of the procedure. A common procedure for the synthesis of macromolecular N⁶-(2-aminoethyl)-NAD(P) derivatives was pursued, coupling N⁶-(2-aminoethyl)-NAD(P) to several water-soluble copolymers containing maleic acid anhydride. PEG (M_r = 20000)-N⁶-(2-aminoethl)-NAD, polyvinylpyrrolidone (M_r,= 160000)-N⁶-(2-aminoethylNAD and dextran (M_r= 70000)-N⁶-(2-aminoethyl)-NAD were synthesized by covalently binding N⁶-(2-aminoethyl)-NAD to the corresponding carboxylated polymers by the carbodiimide method. PEG (M_r= 4000 and 20000-N⁶-(2-aminoethyl)-NADP was efficiently synthesized by covalent attachment of N⁶-(2-aminoethyl)-NADP to N-hydroxy-succinimide activated carboxylate PEG (M_r= 4000 and 20000), avoiding the carbodiimide method, which would lead simultaneously to 2′3′-cyclic NADP derivatives. Except for the macromolecular cofactor derivatives based on copolymers containing maleic acid anhydride, the total enzymatic reducibility of the macromolecular N-(2-aminoethyl)-NAD(P) derivatives was satisfactory (90-95%).     

Preparation of a recyclable novel thermoresponsive affinity copolymer and its application towards ε-polylysine purification

Thermo-responsive polymers have great potential for industrial applications of bio-separation and purification. However, the poor affinity and low recovery of thermoresponsive copolymers are the main factors limiting their large-scale application. In this paper, a recyclable thermoresponsive affinity copolymer (P_NHM-IDA-Ni²⁺) was prepared by immobilizing nickel ions (Ni²⁺) on copolymer P_NHM, and P_NHM-IDA-Ni²⁺ was applied to the purification of ε-polylysine. The lower critical solution temperature (LCST) of P_NHM and P_NHM-IDA-Ni²⁺ were 31.0 °C and 34.0 °C, respectively. Additionally, the recoveries of both copolymers were over 95.0%. The main parameters, such as pH were investigated to optimize the adsorption conditions. In addition, the Langmuir and Freundlich adsorption models were used to predict the maximum adsorption capacity of ε-polylysine. The results of the affinity precipitation demonstrated that the maximum adsorption capacity was 42.9 mg/g, and the adsorption was considered to follow the mono-layer model. The thermodynamic parameters (ΔG⁰, ΔH⁰ and ΔS⁰) of the ε-polylysine adsorption indicated that the adsorption was spontaneous and exothermic. The maximum elution recovery (93.5%) was achieved at pH 5.0 with 0.2 M imidazole. The results of tricine-SDS-PAGE and HPLC (Purity: increased from 84% to 99%) showed that the ε-polylysine was well separated from the crude extract by using the affinity copolymer P_NHM-IDA-Ni²⁺.     

Synthesis of Arg–Gly–Asp (RGD) Sequence Conjugated Thermo-Reversible Gel via the PEG Spacer Arm as an Extracellular Matrix for a Pheochromocytoma Cell (PC12) Culture

Adhesion molecules composed of Gly–Arg–Gly–Asp–Ser (GRGDS) peptides and cell recognition ligands were inculcated into thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 3400) used as a biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was studied in vitro for its ability to promote cell spreading and to increase the viability of cells by introducing PEG spacers. Hydrogel lacking the adhesion molecules proved to be a poor ECM for adhesion, permitting only a 20% spread of the seeded cells after 10 days. When PEG spacer arms, immobilized by a peptide linkage, had been integrated into the hydrogel, conjugation of RGD promoted cell spread by 600% in a 10-day trial. In addition, in a serum-free medium, only GRGDS peptides conjugated with the spacer arm were able to promote cell spread. In terms of the cell viability, GRGDS peptides conjugated with the PEG-carrying copolymer gel specifically mediated cell spread. This result supports the theory that specific recognition is the result of interaction between the integrin families on the fibroblast, and the RGD sequence on the p(NiPAAm-co-PEG) copolymer gel.     

Enzyme immobilization on ultrafine cellulose fibers via poly(acrylic acid) electrolyte grafts

Ultrafine cellulose fiber (diameter 200-400 nm) surfaces were grafted with polyacrylic acid (PAA) via either ceric ion initiated polymerization or methacrylation of cellulose with methacrylate chloride (MACl) and subsequent free-radical polymerization of acrylic acid. PAA grafts by ceric ion initiated polymerization increased with increasing reaction time (2-24 h), monomer (0.3-2.4 M), and initiator (1-10 mM) concentrations, and spanned a broad range from 5.5-850%. PAA grafts on the methacrylated cellulose fibers also increased with increasing molar ratios of MACl to cellulosic hydroxyl groups (MACl/OH, 2-6.4) and monomer acrylic acid (AA) to initiator potassium persulfate (KPS) ratios ([AA]/[KPS], 1.5-6), and were in a much narrower range between 12.8% and 29.4%. The adsorption of lipase (at 1 mg/ml lipase and pH 7) and the activity of adsorbed lipase (pH 8.5, 30 degrees C), in both cases decreased with increasing PAA grafts. The highest adsorption and activity of the lipase on the ceric ion initiated grafted fibers were 1.28 g/g PAA and 4.3 U/mg lipase, respectively, at the lowest grafting level of 5.5% PAA, whereas they were 0.33 g/g PAA and 7.1 U/mg lipase, respectively, at 12.8% PAA grafts on the methacrylated and grafted fibers. The properties of the grafted fibers and the absorption behavior and activity of lipase suggest that the PAA grafts are gel-like by ceric-initiated reaction and brush-like by methacrylation and polymerization. The adsorbed lipase on the ceric ion-initiated grafted surface possessed greatly improved organic solvent stability over the crude lipase. The adsorbed lipases exhibited 0.5 and 0.3 of the initial activity in the second and third assay cycles, respectively.     

Behavior of human immunoglobulin G adsorption onto immobilized Cu(II) affinity hollow‐fiber membranes

Iminodiacetic acid (IDA) and tris(2‐aminoethyl)amine (TREN) chelating ligands were immobilized on poly(ethylene vinyl alcohol) (PEVA) hollow‐fiber membranes after activation with epichlorohydrin or butanediol diglycidyl ether (bisoxirane). The affinity membranes complexed with Cu(II) were evaluated for adsorption of human immunoglobulin G (IgG). The effects of matrix activation and buffer system on adsorption of IgG were studied. Isotherms of batch IgG adsorption onto finely cut membranes showed that neither of the chelates, IDA‐Cu(II) or TREN‐Cu(II), had a Langmuirean behavior with negative cooperativity for IgG binding. A comparison of equilibrium and dynamic maximum capacities showed that the dynamic capacity for a mini‐cartridge in a cross‐flow filtration mode (52.5 and 298.4 mg g^?1 dry weight for PEVA‐TREN‐Cu(II) and PEVA‐IDA‐Cu(II), respectively) was somewhat higher than the equilibrium capacity (9.2 and 73.3 mg g^?1 dry weight for PEVA‐TREN‐Cu(II) and PEVA‐IDA‐Cu(II), respectively). When mini‐cartridges were used, the dynamic adsorption capacity of IDA‐Cu(II) was the same for both mini‐cartridge and agarose gel. Copyright © 2013 John Wiley & Sons, Ltd.     

Controlling the physical behavior and biological performance of liposome formulations through use of surface grafted poly(ethylene glycol)

The presence of poly(ethylene glycol) (PEG) at the surface of a liposomal carrier has been clearly shown to extend the circulation lifetime of the vehicle. To this point, the extended circulation lifetime that the polymer affords has been attributed to the reduction or prevention of protein adsorption. However, there is little evidence that the presence of PEG at the surface of a vehicle actually reduces total serum protein binding. In this review we examine all aspects of PEG in order to gain a better understanding of how the polymer fulfills its biological role. The physical and chemical properties of the polymer are explored and compared to properties of other hydrophilic polymers. An evidence based assessment of several in vitro protein binding studies as well as in vivo pharmacokinetics studies involving PEG is included. The ability of PEG to prevent the self-aggregation of liposomes is considered as a possible means by which it extends circulation longevity. Also, a dysopsonization phenomenon where PEG actually promotes binding of certain proteins that then mask the vehicle is discussed.     

Synthesis and flocculation property in dye solutions of β-cyclodextrin-acrylic acid-[2-(Acryloyloxy)ethyl] trimethyl ammonium chloride copolymer

In aqueous solution a cationic copolymer, poly (β-CD-AA-DMC) was synthesized via free radical copolymerization of acrylic acid (AA) esterified β-CD (β-CD-AA), and a cationic monomer [2-(Acryloyloxy)ethyl] trimethyl ammonium chloride (DMC). The copolymer's structure, morphology and thermal stability were demonstrated by FT-IR, ¹H NMR, SEM and TGA analysis. The flocculation properties of the copolymer were evaluated by the decolorization solutions of two reactive dyes using a jar test method. The decolorization efficiency is influenced by both the nature of the anionic dyes and the pH of the initial dye solution. Electrostatic adsorption played a more important role in flocculation of dyes than bridging of the polymer. Moreover, the inorganic salt decreased the efficiency of color removal.     

Removal of chromium (VI) using poly(methylacrylate) functionalized guar gum

Using persulfate/ascorbic acid redox pair, poly(methylacrylate) was grafted on to guar gum and the conditions for the grafting were optimized. The copolymer sample having maximum %G was evaluated for the removal of Cr(VI) and the sorption conditions were optimized. The sorption was found pH dependent, pH 1.0 being the optimum value. Sorption data at pH 1.0 were modeled using both the Langmuir and Freundlich isotherms where the data fitted better to Freundlich isotherm. The equilibrium sorption capacity of 29.67 mg/g was determined from the Langmuir isotherm. The sorption followed a pseudo-second-order kinetics with a rate constant 2.5 × 10^?4 g mg^?1 min^?1. The grafted product was also evaluated for Cr(VI) removal from local electroplating industrial waste water. The regeneration experiments revealed that the guar-graft-poly(methylacrylate) could be successfully reused for five cycles. In the present study conductivity measurements were used instead of conventional photometric method for determining Cr(VI) concentration in the equilibrium solutions and the results obtained have been compared with photometric method. Optimum Cr(VI) binding under highly acidic conditions indicated significant contribution of non electrostatic forces in the adsorption process.