Synthesis of discrete allyl-functional polyethylene glycol for efficient hydrophilization of dihydr (polydimethylsiloxane)

Amphiphilic poly(ethylene glycol)-block-pol (dimethylsiloxane)-block-poly(ethylene glycol)(PEG-block-PDMS block-PEG) triblock copolymers have been successfully prepared via hydrosilylation using discrete and polydisperse PEG of various chain lengths. Facile synthesis of discrete PEG (dPEG) is achieved via systematic tosylation and etherification of lower glycols. Amphiphilicity of the dPEG block-PDMS-block-dPEG triblock copolymer is illustrated by dynamic light scattering (DLS) and measurement of the critical micelle concentration (CMC).

Low temperature pretreatment of sugarcane bagasse at atmospheric pressure using mixtures of ethylene carbonate and ethylene glycol

A low temperature lignocellulose pretreatment process was developed using acid-catalysed mixtures of alkylene carbonate and alkylene glycol. Pretreatment of sugarcane bagasse with mixtures of ethylene carbonate (EC) and ethylene glycol (EG) was more effective than that with mixtures of propylene carbonate (PC) and propylene glycol (PG). These mixtures were more effective than the individual components in making bagasse cellulose more amenable to cellulase digestion. Glucan digestibilities of ≥87% could be achieved with a wide range of EC to EG ratios from 9:1 to 1:1 (w/w). Pretreatment of bagasse by the EC/EG mixture with a ratio of 4:1 in the presence of 1.2% H2SO4 at 90 °C for 30 min led to the highest glucan enzymatic digestibility of 93%. The high glucan digestibilities obtained under these acidic conditions were due to (a) the ability of alkylene carbonate to cause significant biomass size reduction, (b) the ability of alkylene glycol to cause biomass defibrillation, (c) the ability of alkylene carbonate and alkylene glycol to remove xylan and lignin, and (d) the magnified above attributes in the mixtures of alkylene carbonate and alkylene glycol.

Effect of dangling chains on the structure and physical properties of a tightly crosslinked poly(ethylene glycol) network

Major imperfections in crosslinked polymers include loose or dangling chain ends that lower the crosslink d., thereby reducing elastic recovery and increasing the solvent swelling. These imperfections are hard to detect, quantify and control when the network is initiated by free radical reactions. As an alternative approach, the sol-​gel synthesis of a model poly(ethylene glycol) (PEG-​2000) network is described using controlled amts. of bis- and mono-​triethoxy silyl Pr urethane PEG precursors to give silsesquioxane (SSQ, R-​SiO1.5) structures as crosslink junctions with a controlled no. of dangling chains. The effect of the no. of dangling chains on the structure and connectivity of the dried SSQ networks has been detd. by step-​crystn. differential scanning calorimetry. The role that micelle formation plays in controlling the sol-​gel PEG network connectivity has been studied by dynamic light scattering of the bis- and mono-​triethoxy silyl precursors and the networks have been characterized by 29Si solid state NMR, sol fraction and swelling measurements. These show that the dangling chains will increase the mesh size and water uptake. Compared to other end-​linked PEG hydrogels, the SSQ-​crosslinked networks show a low sol fraction and high connectivity, which reduces solvent swelling, degree of crystallinity and the crystal transition temp. The increased degree of freedom in segment movement on the addn. of dangling chains in the SSQ-​crosslinked network facilitates the packing process in crystn. of the dry network and, in the hydrogel, helps to accommodate more water mols. before reaching equil.

methoxy-poly(ethylene glycol) modified poly(L-lactide) enhanced cell affinity of human bone marrow stromal cells by the upregulation of 1-cadherin and delta-2-catenin

Poly(l-lactide) (PLLA), a versatile biodegradable polymer, is one of the most commonly-used materials for tissue engineering applications. To improve cell affinity for PLLA, poly(ethylene glycol) (PEG) was used to develop diblock copolymers. Human bone marrow stromal cells (hBMSCs) were cultured on MPEG-b-PLLA copolymer films to determine the effects of modification on the attachment and proliferation of hBMSC. The mRNA expression of 84 human extracellular matrix (ECM) and adhesion molecules was analyzed using RT-qPCR to understand the underlying mechanisms. It was found that MPEG-b-PLLA copolymer films significantly improved cell adhesion, extension, and proliferation.This was found to be related to the significant upregulation of two adhesion genes, CDH1 and CTNND2, which encode 1-cadherin and delta-2-catenin, respectively, two key components for the cadherin-catenin complex. In summary, MPEG-b-PLLA copolymer surfaces improved initial cell adhesion by stimulation of adhesion molecule gene expression.

Controlling microencapsulation and release of micronized proteins using poly(ethylene glycol) and electrospraying

The fabrication of tailored microparticles for delivery of therapeutics is a challenge relying upon a complex interplay between processing parameters and materials properties. The emerging use of electrospraying allows better tailoring of particle morphologies and sizes than current techniques, critical to reproducible release profiles. While dry encapsulation of proteins is essential for the release of active therapeutics from microparticles, it is currently uncharacterized in electrospraying. To this end, poly(ethylene glycol) (PEG) was assessed as a micronizing and solubilizing agent for dry protein encapsulation and release from electrosprayed particles made from polycaprolactone (PCL). The physical effect of PEG in protein-loaded poly(lactic-co-glycolic acid) (PLGA) particles was also studied, for comparison. The addition of 5–15 wt% PEG 6 kDa or 35 kDa resulted in reduced PCL particle sizes and broadened distributions, which could be improved by tailoring the electrospraying processing parameters, namely by reducing polymer concentration and increasing flow rate. Upon micronization, protein particle size was reduced to the micrometer domain, resulting in homogenous encapsulation in electrosprayed PCL microparticles. Microparticle size distributions were shown to be the most determinant factor for protein release by diffusion and allowed specific control of release patterns.

Determination of urinary thymidine glycol using affinity chromatography, HPLC and post-column reaction detection : a biomarker of oxidative DNA damage upon kidney transplantation

Reactive oxygen species are generated during ischaemia-reperfusion of tissue. Oxidation of thymidine by hydroxyl radicals (HO) leads to the formation of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol). Thymidine glycol is excreted in urine and can be used as biomarker of oxidative DNA damage. Time dependent changes in urinary excretion rates of thymidine glycol were determined in six patients after kidney transplantation and in six healthy controls. A new analytical method was developed involving affinity chromatography and subsequent reverse-phase high-performance liquid chromatography (RP-HPLC) with a post-column chemical reaction detector and endpoint fluorescence detection. The detection limit of this fluorimetric assay was 1.6 ng thymidine glycol per ml urine, which corresponds to about half of the physiological excretion level in healthy control persons. After kidney transplantation the urinary excretion rate of thymidine glycol increased gradually reaching a maximum around 48 h. The excretion rate remained elevated until the end of the observation period of 10 days. Severe proteinuria with an excretion rate of up to 7.2 g of total protein per mmol creatinine was also observed immediately after transplantation and declined within the first 24 h of allograft function (0.35 + 0.26 g/mmol creatinine). The protein excretion pattern, based on separation of urinary proteins on sodium dodecyl sulphate-polyacrylamide gel electrophorosis (SDS-PAGE), as well as excretion of individual biomarker proteins, indicated nonselective glomerular and tubular damage. The increased excretion of thymidine glycol after kidney transplantation may be explained by ischaemia-reperfusion induced oxidative DNA damage of the transplanted kidney.

Performance of R-N(R′)-R″ functionalised poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) monolithic sorbent for plasmid DNA adsorption

High-throughput plasmid DNA (pDNA) manufacture is obstructed predominantly by the performance of conventional stationary phases. For this reason, the search for new materials for fast chromatographic separation of pDNA is ongoing. A poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (GMA-EGDMA) monolithic material was synthesised via a thermal-free radical reaction, functionalised with different amino groups from urea, 2-chloro-N,N-diethylethylamine hydrochloride (DEAE-Cl) and ammonia in order to investigate their plasmid adsorption capacities. Physical characterisation of the monolithic polymer showed a macroporous polymer having a unimodal pore size distribution pivoted at 600 nm. Chromatographic characterisation of the functionalised polymers using pUC19 plasmid isolated from E. coli DH5α-pUC19 showed a maximum plasmid adsorption capacity of 18.73 mg pDNA/mL with a dissociation constant (KD) of 0.11 mg/mL for GMA-EGDMA/DEAE-Cl polymer. Studies on ligand leaching and degradation demonstrated the stability of GMA-EGDMA/DEAE-Cl after the functionalised polymers were contacted with 1.0 M NaOH, which is a model reagent for most 'cleaning in place' (CIP) systems. However, it is the economic advantage of an adsorbent material that makes it so attractive for commercial purification purposes. Economic evaluation of the performance of the functionalised polymers on the grounds of polymer cost (PC)/mg pDNA retained endorsed the suitability of GMA-EGDMA/DEAE-Cl polymer.

Treatment of silk fibroin with poly(ethylene glycol) for the enhancement of corneal epithelial cell growth

A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori) and cast into membranes to serve as freestanding templates for tissue-engineered corneal cell constructs to be used in ocular surface reconstruction. In this study, we sought to enhance the attachment and proliferation of corneal epithelial cells by increasing the permeability of the fibroin membranes and the topographic roughness of their surface. By mixing the fibroin solution with poly(ethylene glycol) (PEG) of molecular weight 300 Da, membranes were produced with increased permeability and with topographic patterns generated on their surface. In order to enhance their mechanical stability, some PEG-treated membranes were also crosslinked with genipin. The resulting membranes were thoroughly characterized and compared to the non-treated membranes. The PEG-treated membranes were similar in tensile strength to the non-treated ones, but their elastic modulus was higher and elongation lower, indicating enhanced rigidity. The crosslinking with genipin did not induce a significant improvement in mechanical properties. In cultures of a human-derived corneal epithelial cell line (HCE-T), the PEG treatment of the substratum did not improve the attachment of cells and it enhanced only slightly the cell proliferation in the longer term. Likewise, primary cultures of human limbal epithelial cells grew equally well on both non-treated and PEG-treated membranes, and the stratification of cultures was consistently improved in the presence of an underlying culture of irradiated 3T3 feeder cells, irrespectively of PEG-treatment. Nevertheless, the cultures grown on the PEG-treated membranes in the presence of feeder cells did display a higher nuclear-to-cytoplasmic ratio suggesting a more proliferative phenotype. We concluded that while the treatment with PEG had a significant effect on some structural properties of the B. mori silk fibroin (BMSF) membranes, there were minimal gains in the performance of these materials as a substratum for corneal epithelial cell growth. The reduced mechanical stability of freestanding PEG-treated membranes makes them a less viable choice than the non-treated membranes.

Characterisation of lignins isolated from sugarcane bagasse pretreated with acidified ethylene glycol and ionic liquids

Sugarcane bagasse pretreatment processes using acidified aqueous ethylene glycol (EG) and ionic liquids (ILs) have been reported recently. In this study, recovery of lignins from these processes was conducted, as well as determination of their physico-chemical properties. The amount of lignins recovered from 1-butyl-3-methylimidazolium chloride ([bmim]Cl) with HCl as a catalyst and [bmim][CH3SO3] was ∼42%, and ∼35%–36% by EG with HCl or H2SO4 as a catalyst, respectively. The isolated lignins were characterised using wet chemistry, spectroscopy and thermogravimetry analysis (TGA), and the results compared to soda lignin from NaOH pretreatment of bagasse. The IL and EG lignins contained no or trace amounts of carbohydrates, slightly lower hydrogen content but slightly higher oxygen contents than soda lignin. The IL and EG lignins contained more C-3 and C-5 reactive sites for Mannich reaction and had more p-hydroxypheny propane unit structures than soda lignin. Two-dimensional heteronuclear single quantum coherence (2D HSQC) nuclear magnetic resonance (NMR) identified the major substructural units in the lignins, and allowed differences among them to be studied. As EG lignins were extracted in very reactive environment, intermediate enol ethers were formed and led to cleavage reactions which were not apparent in the other lignins. 31P NMR and infra-red spectroscopy results showed that IL and EG lignins had lower total hydroxyl content than soda lignin, probably indicating that a higher degree of self-polymerisation occurred during bagasse pretreatment, despite the use of lower temperature and shorter reaction time. On the basis of the salient features of these lignins, potential applications were proposed.

Thermal Analysis of Polypropylene Hydroperoxide

Studies on the low temperature oxidation of polyolefins have been the subject matter of several investigations because of interest in understanding the aging and weathering of polymers. One of the key steps in such an oxtdatton is the formation of hydroperoxide. Estimation of the hydroperoxide in oxidized samples, which is conventionally done by iodometric titrations, is quite important to gain knowledge about the kinetics and mechanism of the process. The present investigation is the first report of the thermal analysis of polypropylene hydroperoxide samples from two angles: (1) the thermal behavior of its decomposition and (2) whether such an analysis leads to knowledge of the concentration of hydroperoxide in the sample.

Properties Of Castor Oil Impregnated All-Polypropylene And Polypropylene-Paper Capacitors

In view of its non-toxicity, and good dielectric properties, castor oil, a polar liquid dielectric of vegetable origin is suggested as a possible alternative to PCB's for capacitor applications. In this paper the dielectric properties (including partial discharge behavior), of all-polypropylene and paper-polypropylene capacitors with castor oil as impregnant, are reported. The paper also contains results of life studies conducted under accelerated electrical and thermal stresses when they are occurring both individually and combined. The data obtained have been statistically analyzed and approximate life of the system calculated bylinear extrapolation.