Model process for separation based on unfolding and refolding of chymotrypsin inhibitor 2 in thermoseparating polymer two-phase systems

For the design of a new separation process based on unfolding and refolding of protein, the partitioning behaviour of proteins was studied in thermoseparating polymer two-phase systems with varying pH and temperature. Chymotrypsin inhibitor 2 (CI2), which unfolds reversibly in a simple two-state manner, was partitioned in an aqueous two-phase system (ATPS) composed of a random copolymer of ethylene oxide and propylene oxide (Breox) and dextran T-500. Between 25 and 50 degrees C, the partition coefficients of CI2 in Breox-dextran T-500 systems remain constant at neutral pH. However, there is a drastic increase at pH values below 1.7, 2.1, and 2.7 at 25, 40 and 50 degrees C, respectively. The partitioning behavior of CI2 was also investigated in thermoseparating water-Breox systems at 55-60 degrees C, where CI2 was partitioned to the polymer-rich phase at pH values below 2.4. These results on the CI2 partitioning can be explained by the conformational difference between the folded and the unfolded states of the protein, where the unfolded CI2 with a more hydrophobic surface is partitioned to the relatively hydrophobic Breox phase in both systems. A separation process is presented based on the partitioning behavior of unfolded and refolded CI2 by control of pH and temperature in thermoseparating polymer two-phase systems. The target protein can be recovered through (i) selective separation in Breox-dextran systems, (ii) refolding in Breox phase, and (iii) thermoseparation of primary Breox phase.     

Influence of poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) triblock copolymers on stereoselective catalysis in water

The first application of (EO)_n‐(PO)_m‐(EO)_n triblock copolymers as surfactants in asymmetric hydrogenation is described. We observed a dependence of the activity and enantioselectivity on the asymmetric hydrogenation of methyl (Z)‐α‐acetamidocinnamate on the length of the (PO)_m domain of the copolymer. The activity and enantioselectivity were observed to be independent of the hydrophilic‐lipophilic‐balance (HLB) or the critical micelle concentration (cmc) of the copolymer. The size of the (EO)_n unit does not play an important role, however the addition of a small amount of SDS enhances the enantioselectivities significantly. The triblock copolymers were also successfully used as phase transfer reagent in two‐phase Suzuki carbon‐carbon coupling reactions. The use of polymeric reagents in micellar and phase‐transfer systems has the advantage that these reagents can be easily separated from the reaction mixture by means of a membrane.     

Side-chain liquid-crystalline polymers containing siloxane spacer, 3. Thermal properties of copolymers containing different types of mesogens

Copolymerization of monomers containing the disiloxane unit in the spacer component and linear triple-core mesogens with comonomers containing linear double-core mesogens, or laterally attached triple-core mesogens was carried out radically. The effect of copolymer composition and monomer structure on the mesomorphic properties of the obtained copolymers was investigated in detail. The copolymers with a comonomer content up to 50 mol-%, exhibit an enantiotropic nematic phase, whereas the parent homopolymers containing triple-core mesogens exhibit a smectic phase. The copolymer containing more than 50 mol-% of the comonomer shows no mesophase. The isotropization temperature of the copolymers decreases with increasing comonomer content. However, the glass transition temperature is almost unchanged upon introduction of the comonomer unit. In case of copolymers containing laterally attached mesogens, a smectic phase was observed below the temperature range of the nematic phase. Consequently, the mesophase and the temperature range of the liquid-crystalline state can be controlled by the introduction of the comonomer unit whose parent homopolymer does not exhibit any mesophase.     

Antithrombogenicity and oxygen permeability of block and graft copolymers of polydimethylsiloxane and poly(alpha-amino acid)

A-B-A-type block copolymers consisting of poly(alpha-amino acid) as A component and polydimethylsiloxane as B component and graft copolymers consisting of polydimethylsiloxane as trunk polymer and poly(alpha-amino acid) as branch polymer were synthesized. gamma-Benzyl-L- or DL-glutamate, epsilon-benzyloxycarbonyl L-lysine, and sarcosine were used as alpha-amino acid. Different microphase-separated structures were found on the film surface according to the copolymer composition and the casting conditions. In vitro antithrombogenicity test showed higher antithrombogenicity of block or graft copolymers than homopolymers. The best antithrombogenicity was independent of the kind of alpha-amino acid and the degree of polymerization of copolymers. The best ratio was 65-75% in block copolymer and 40-50% in the case of graft copolymer. The oxygen permeability of block and graft copolymer film was intermediate between those of homopolymers and varied with changing the composition of the copolymer. These experiments showed that the microphase-separated structure on the film surface was most important both for the antithrombogenicity and oxygen permeability of these copolymer films.     

Novel Polyesteramide‐Based Diblock Copolymers: Synthesis by Ring‐Opening Copolymerization and Characterization

Block copolymers based on a polyesteramide sequence and a polyether block were synthesized in bulk at 250 °C by ring‐opening copolymerization (ROP) of ε‐caprolactone (CLo) and ε‐caprolactam (CLa) as initiated by Jeffamine® M1000, i.e., ω‐NH₂ copoly[(ethylene oxide)‐co‐(propylene oxide)] copolymer [P(EO‐co‐PO)‐NH₂]. For an initial molar ratio of [CLa]₀/[CLo]₀ = 1, the copolymerization allowed for the formation of a diblock copolymer with a statistical polyesteramide sequence, as evidenced by ¹³C NMR. Investigation of the ROP mechanism highlighted that CLo was first polymerized, leading to the formation of a diblock copolymer P(EO‐co‐PO)‐b‐PCLo‐OH, followed by CLa hydrolysis to aminocaproic acid that inserted into the ester bonds of PCLo via aminolysis and subsequent condensation reactions. The outcome is the selective formation of P(EO‐co‐PO)‐b‐P(CLa‐co‐CLo)‐OH diblock copolymers where the composition and length of the polyesteramide sequence can be fine‐tuned by the [CLa]₀/[CLo]₀ and ([CLa]₀ + [CLo]₀)/[P(EO‐co‐PO)‐NH₂]₀ initial molar ratios.     

Structure of Polybutadienes Synthesised with a New Catalyst System, 3. Random Copolymers of trans‐1,4‐ and 1,2‐Polybutadiene

The structure and phase composition of random copolymers based on mesomorphic trans‐1,4‐polybutadiene containing a different amount of vinyl units (2–41 mol‐%) were studied at various temperatures by X‐ray analysis and differential scanning calorimetry. As the amount of 1,2‐units in the polymer increases, temperatures of the phase transitions crystal‐mesophase and mesophase‐melt decrease, thus leading to a more narrow temperature range corresponding to an existence of the mesomorphic state. At a concentration of alien units of about 30 mol‐%, the copolymer loses the ability to form a mesophase. Upon a further increase of 1,2‐unit content (35–40 mol‐%), the copolymer no longer crystallizes. The phase diagram of the copolymer is discussed in relation of temperature of phase transitions versus composition. It was shown that the destruction of the regular structure of the mesophase polymer by incorporation of alien units in its main chain leads to substantial decrease of the tendency of the material to mesomorphism, even more strongly than its ability to crystallize.     

Nonfouling biomaterials based on polyethylene oxide-containing amphiphilic triblock copolymers as surface modifying additives: protein adsorption on PEO-copolymer/polyurethane blends

Surface modification of a segmented polyurethane was achieved by blending with novel PEO-containing amphiphilic triblock copolymers (PEO-polyurethane-PEO). Three copolymers having different PEO MW (550, 2000, 5000) were used as surface modification additives. The protein resistance of the blend surfaces was evaluated using radiolabeling methods. On the blends of copolymers with PEO blocks of MW 2000 and 5000, fibrinogen adsorption from physiologic buffer decreased with increasing copolymer content up to 20 wt%. On the blends with PEO blocks of MW 550, resistance to adsorption for a given copolymer content was much greater. For all three blend types at 20% copolymer content, reductions in adsorption compared to the unmodified PU matrix were greater than 95%. Reductions in adsorption were similar for the 20% blends and surfaces prepared by coating the copolymers directly on the matrix, suggesting that the 20% blend surfaces were completely covered by copolymer. At low copolymer content (< or =10 wt %), fibrinogen adsorption decreased with decreasing PEO block length. This was probably due to increasing surface coverage of the copolymers with decreasing block length. It is therefore concluded that surface density of PEO is more important than PEO MW for the protein resistance of these surfaces. Lysozyme, a much smaller protein, showed adsorption trends similar to fibrinogen. The adsorption of fibrinogen and lysozyme from binary solutions to blends of the copolymer with PEO blocks of 2000 MW was investigated to probe the effects of protein size on adsorption resistance. Fibrinogen and lysozyme showed similar fractional decreases in adsorption relative to the PU matrix independent of the surface density of PEO. However lysozyme was enriched in the surface relative to the solution, that is, it was adsorbed preferentially to fibrinogen.     

In vitro and in vivo degradation studies of a novel linear copolymer of lactide and ethylphosphate

Poly(lactide-co-ethylphosphate)s, a new class of linear phosphorus-containing copolymers made by chain-extending low-molecular-weight polylactide prepolymers with ethyl dichlorophosphate, were investigated for their in vitro and in vivo degradation mechanism and kinetics. Microspheres made from poly(lactide-co-ethylphosphate) were studied under both accelerated and normal in vitro degradation conditions. Gel permeation chromatography (GPC), 1H- and 31P-NMR, weight loss measurements, and differential scanning calorimetry (DSC) techniques were used to characterize the change of molecular weight (M(w)), chemical composition, and glass transition temperature (T(g)) of the degrading polymers. The results indicated that the copolymers degraded in a two-stage fashion, with cleavage of the phosphate-lactide linkages contributing mostly to the initial more rapid degradation phase and cleavage of the lactide-lactide bonds being responsible for the slower latter stage degradation. The decrease in the copolymer M(w) was accompanied by a continuous mass loss. Results from the accelerated degradation studies confirmed that the copolymers degraded into various monomers of the copolymers, which were non-toxic and biocompatible. A two-stage hydrolysis pathway was thus proposed to explain the degradation behavior of the copolymers. In vivo degradation studies performed in mice demonstrated a good in vitro and in vivo correlation for the degradation rates. In vivo clearance of the polymer was faster and without any lag phase. These copolymers are potentially advantageous for drug delivery and other biomedical applications where rapid clearance of the polymer carrier and repeated dosing capability are essential to the success of the treatment.     

Propriétés physiques et mécaniques d'un copolymère séquencé polystyrène-polyisoprène-polystyrène hydrogéné

Differential scanning calorimetry (DSC) and stress-strain measurements have been made on a polyisoprene hydrogenated polystyrene-polyisoprene-polystyrene (SIS) elastomeric block copolymer and compared with those of the corresponding nonhydrogenated copolymer. The SIS copolymer was prepared by anionic polymerization with butyllithium in benzene. Both polymers are two-phase amorphous elastomeric materials displaying two glass transition temperatures. The transition temperature of the hydrogenated polyisoprene phase is only 4°C higher than that of the polyisoprene phase in the unhydrogenated material. Stress-strain curves measured on solvent cast films before and after hydrogenation show identical behaviors at low elongation. Both the tensile strength and elongation at break are smaller for the hydrogenated polymer. Comparison between the stress-strain curves measured in successive extension cycles shows that this polymer does not exhibit the “leathery” behavior generally observed for SIS elastomeric block copolymers, but behaves more like a typical vulcanized elastomer. This would indicate more rigid and much better separated polystyrene particles in the hydrogenated system.     

Low temperature formation of calcium-deficient hydroxyapatite-PLA/PLGA composites

Hydroxyapatite-biodegradable polymer composites have been formed by a low temperature chemical route. Precomposite structures were prepared by combining alpha-Ca(3)(PO(4))(2) (alpha-tricalcium phosphate or alpha-TCP) with poly(L-lactic) acid and poly(DL-lactide-co-glycolide) copolymers. The final composite structure was achieved by in situ hydrolysis of alpha-TCP to Ca(9)(HPO(4))(PO(4))(5)OH (calcium deficient hydroxyapatite or CDHAp) either in solvent cast or pressed precomposites. Hydrolysis was performed at 56 degrees C-a temperature slightly above the glass transition of the polymers. The effects of polymer chemistry, composite formation technique, and porosity on hydrolysis kinetics and degree of transformation were examined with isothermal calorimetry, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and scanning electron microscopy. Calorimetric data and XRD analyses revealed that hydrolysis reactions were inhibited in the presence of the polymers. Isothermal calorimetry indicated the extent of the alpha-TCP to CDHAp transformation in 24 h to be 85% in the solvent cast composites containing PLGA (85:15) copolymer; however, XRD analyses suggested almost complete reaction. The CDHAp formation extent was 26% for the pressed composites containing the same polymer. In the presence of NaCl as a pore generator, 81% transformation was observed for the pressed composites. This transformation occurred without any chemical reaction between the polymer-inorganic components, as determined by Fourier transform infrared spectroscopy. Minimal transformation to CDHAp occurred in composites containing poly(L-lactic) acid.     

Temperature and pH dependence of the catalytic activity of colloidal platinum nanoparticles stabilized by poly[(vinylamine)‐co‐(N‐vinylisobutyramide)

Colloidal platinum nanoparticles in the size range of 5–35 Å have been successfully prepared in water at room temperature by NaBH₄ reduction of ionic platinum in the presence of poly[(vinylamine)‐co‐(N‐vinylisobutyramide)] (PVAm‐co‐PNVIBA). To our knowledge, the temperature‐ and pH‐responsive copolymer was used for the first time as the stabilizer of colloidal metal particles. Three PVAm‐co‐PNVIBA copolymers with PVAm contents of 4.1, 8.3, and 19.8 mol‐% were examined. The particle size and morphology of the platinum colloids varied with the copolymer composition, as confirmed by TEM measurements. The polymer‐stabilized Pt nanoparticles precipitated on heating above their critical flocculation temperatures (CFTs), which were strongly dependent on the solution pH and the copolymer composition. The CFTs were 0.2–1.6°C lower than the lower critical solution temperatures (LCSTs) of the copolymers free in water and the differences increased with increasing PVAm content. The catalytic activity of the Pt nanoparticles was investigated in the aqueous hydrogenation of allyl alcohol. It was found that the activity was regulated through temperature‐ and pH‐induced phase separation. The PVAm content also strongly effected the catalytic activity and the morphology of phase separated catalysts. With a PVAm content of 4.1 mol‐%, the colloidal platinum sol reversibly changed its catalytic activity with changes in temperature.     

Gas permeability of the film of block and graft copolymers of polydimethylsiloxane and poly(gamma-benzyl L-glutamate)

A-B-A type block copolymers of poly(gamma-benzyl L-glutamate) (PBLG, A segment) and polydimethylsiloxane (PDMS, B segment) and PDMS (trunk)-PBLG (branch) graft copolymers were synthesized, and the permeation of oxygen in water and the permeation of oxygen and carbon dioxide in the dry state were investigated. The gas permeation coefficient (P) increased with increasing content of PDMS. However, PCO2/PO2 values of copolymer films were in the range 6-9, i.e. larger than 5.4 for PDMS film. The oxygen permeation in water suffered from the interfacial resistance, which was reduced by the hydrolysis of film surface. The Arrhenius plot of the gas permeation coefficient in the dry state of the block copolymer B showed a turning point at about 40 degrees C. This temperature is close to beta-peak temperature (39 degrees C) and may be ascribed to the molecular motion of the PBLG segment. Transmission electron microscopy showed that one of the block copolymer films (PDMS 46 mol%) appears to have PDMS segments dispersed in the PBLG matrix (island-in-sea structure) and one of the graft copolymer films (PDMS 58 mol%) appears to take a lamellar structure. The gas permeation across the graft copolymer film appears to occur through the continuous PDMS phase, leading to a near-negligible activation energy in this process.     

Synthesis and Characterization of Epoxidized Styrene‐Butadiene Block Copolymers as Templates for Nanostructured Thermosets

Summary: A wide range of epoxidized styrene‐block‐butadiene block copolymers were synthesized using hydrogen peroxide in the presence of an in situ prepared methyltrioctylammoniumtetrakis(diperoxotungstate)phosphate as the catalyst system in a water/dichloroethane biphasic system. ¹H NMR and FT‐IR spectra revealed that the epoxidation procedure led mainly to 1,4‐epoxidized butadiene units. GPC analysis showed that epoxidation changed the copolymer architecture into stars with fewer arms. The copolymers showed two glass transition temperatures in accordance with the phase separation for block copolymers and, as revealed in AFM images, the self‐assembly takes place on a nanometer scale. Moreover, epoxidized styrene‐butadiene (SB) copolymers showed improved miscibility with epoxy monomers leading to self‐assembled nanostructures in the uncured state. This allows them to be used as templates for nanostructured resins.

TM‐AFM phase images for: a) 40 mol‐% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.‐% DGEBA in 50 mol‐% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.     

Development of injectable, resorbable drug-releasing copolymer scaffolds for minimally invasive sustained ophthalmic therapeutics

Copolymers based on N-isopropylacrylamide (NIPAAm), acrylic acid N-hydroxysuccinimide (NAS) and varying concentrations of acrylic acid (AA) and acryloyloxy dimethyl-γ-butyrolactone (DBA) were synthesized to create thermoresponsive, resorbable copolymers for minimally invasive drug and/or cell delivery to the posterior segment of the eye to combat retinal degenerative diseases. Increasing DBA content was found to decrease both copolymer water content and lower critical solution temperature. The incorporation of NAS provided an amine-reactive site, which can be exploited for facile conjugation of bioactive agents. Proton nuclear magnetic resonance analysis revealed the onset of hydrolysis-dependent opening of the DBA lactone ring, which successfully eradicated copolymer phase transition properties and should allow the gelled polymer to re-hydrate, enter systemic circulation and be cleared from the body without the production of degradation byproducts. Hydrolytic ring opening occurs slowly, with over 85% copolymer mass remaining after 130 days of incubation in 37°C phosphate buffered saline. These slow-degrading copolymers are hypothesized to be ideal delivery vehicles to provide minimally invasive, sustained, localized release of pharmaceuticals within the posterior segment of the eye to combat retinal degenerative diseases.     

Extended delivery of the antimitotic agent colchicine from thermoresponsive N-isopropylacrylamide-based copolymer films to human vascular smooth muscle cells

The aim of this study was to establish the capacity of thermoresponsive poly(N-isopropylacrylamide) copolymer films to deliver bioactive concentrations of an antimitotic agent to human vascular smooth muscle cells (HASMC) over an extended period of time. Copolymer films were prepared using a 50:50 (w/w) ratio of N-isopropylacrylamide (NiPAAm) monomer to the more hydrophobic N-tert-butylacrylamide (NtBAAm) and loaded with the antimitotic agent colchicine (0.1 micromol per film) at room temperature. Colchicine release from films was sustained over a 14-day period. At 24 h postloading, the concentration of colchicine in the medium overlying films was 2.12 +/- 0.16 microM; this fell to 0.20 +/- 0.01 microM at 7 days and decreased further to 0.12 +/- 0.01 microM after 14 days. Colchicine released from copolymer films inhibited proliferation when subsequently placed on HASMC: at 0.1 microM, released colchicine reduced proliferation to 18.5 +/- 0.8% of control cells (p < 0.001, n = 9). The antiproliferative effect of released colchicine was comparable to that of native colchicine, as observed in separate experiments. Furthermore, colchicine released from 50:50 polymer films inhibited the proliferation of cells grown in the same environment as the copolymer. Inhibition of cell proliferation was not due to the release of cytotoxic particles from the copolymer because medium incubated with copolymer for 5 days and then applied to HASMC did not alter cell viability. In conclusion, this study demonstrates that 50:50 NiPAAm:NtBAAm copolymers can deliver bioactive concentrations of the antimitotic agent colchicine to human vascular cells over an extended period of time.     

Compatibilizing Effect of Transesterification Copolymers on Bisphenol‐A Polycarbonate/Poly(ethylene terephthalate) Blends

After considerably long time of transesterification reactions between poly(ethylene terephthalate) (PET) and bisphenol‐A polycarbonate (PC) in the molten state, random copolymers, referred to be TCET's, can be obtained, which have fairly good compatibilizing effect on the immiscible PC/PET blend. The compatibilizing effect of these transesterification random copolymers is proved to be closely related to their compatibility with PET and PC. Being completely compatible both with PET and PC, the TCET50 copolymer with 50 wt.‐% ethylene terephthalate content is an efficient compatibilizer, it can greatly improve the compatibility between PET and PC. With increasing content of the TCET50 copolymer in the PC/PET/TCET50 ternary blend, the two glass transition temperatures, which belong to the PET‐rich and PC‐rich phase respectively, approach each other gradually. When the content of the TCET50 copolymer in the blend reaches 60 wt.‐%, only one glass transition temperature can be detected by differential scanning calorimetry (DSC). The TCET30 and TCET70 copolymer, which have 30 and 70 wt.‐% ethylene terephthalate content respectively, are less efficient in compatibilizing the PC/PET blend, since the TCET30 copolymer and PET, as well as the TCET70 copolymer and PC, are compatible to a certain degree instead of being completely compatible.     

Block Copolymers Have Differing Adjuvant Effects on the Primary Immune Response Elicited by Genetic Immunization and on Further Induced Allergy

Block copolymers were recently used to promote gene delivery in various tissues. Using a plasmid encoding a food allergen, bovine β-lactoglobulin (BLG), we studied the effects of block copolymers on gene expression levels and primary immune response and on further induced allergy. Block copolymers (i.e., Tetronic 304, 908, and 1107) and various quantities of DNA were injected into the tibialis muscles of BALB/c mice. The BLG levels in injected muscle and the BLG-specific induced immune response were analyzed after injection. DNA-immunized mice were further experimentally sensitized with BLG, and the effects of block copolymer and DNA doses on allergic sensitization and elicitation were compared. Tetronic 304 induced a 12-fold increase in BLG production, while Tetronic 1107 increased the duration of BLG expression. Different Th1 primary specific immune responses were observed, either strong humoral and cellular (304), only cellular (1107), or weak cellular and humoral (908) responses. After BLG sensitization, increased BLG-specific IgG2a production was observed in all groups of mice independently of the presence and nature of the block copolymer. Increased BLG-specific IgG1 production was also detected after sensitization, except with Tetronic 1107. Compared with naked DNA, Tetronic 304 was the only block polymer that decreased BLG-specific IgE concentrations. However, after allergen challenge, Tetronic 1107 was the only block copolymer to reduce eosinophils and Th2 cytokines in bronchoalveolar lavage (BAL) fluid. Tetronic 304 amplified local inflammation. Each block copolymer elicited a different immune response, although always Th1 specific, in BALB/c mice.We previously demonstrated that DNA immunization using the β-lactoglobulin (BLG) gene, one of the major cow''s milk allergens, elicited a Th1-specific immune response that inhibited Th2 cell induction and prevented further allergic sensitization (2). This approach has also been successfully applied to allergens from pollen, latex, and peanut (for a review, see reference 23). However, patients with cow''s milk allergy are predominantly multisensitized, i.e., they produce IgE directed against more than one cow''s milk protein (22). Moreover, many allergic patients are polyallergic, i.e., they are allergic to various allergens (food, pollen, and dust). Putative use of DNA delivery in allergy would therefore imply multigene immunization, i.e., the administration of a pool of plasmids containing the cDNAs of different allergens. This suggests that decreasing quantities of DNA should be used to determine the minimal quantity of plasmid necessary to decrease the IgE level after sensitization. In this context, adjuvants such as block copolymers, which promote the expression of various reporter genes, e.g., luciferase and β-galactosidase genes (11, 12, 16), are of interest.Block copolymers are synthesized using propylene oxide (PO) and ethylene oxide (EO), which are organized as “blocks” of polyoxyethylene (POE) and polyoxypropylene (POP). These copolymers can be designed and synthesized using various amounts of PO and EO and with differential arrangements of POP and POE blocks. Block copolymers are used for their adjuvant capacities (for a review, see reference 21) and were recently found to promote gene delivery in tissues, such as skeletal and cardiac muscle (11, 15-18), lung (8), and eyes (12). Copolymers can be used to increase the intensity and/or duration of the expression of reporter genes, such as those encoding green fluorescent protein (GFP) or luciferase, but also of therapeutic genes, such as those encoding erythropoietin or dystrophin. We used poloxamine block copolymers, which have a tetrafunctional structure consisting of four PEO/POP blocks centered on an ethylenediamine moiety (15). The DNA delivery efficiencies of 3 nonionic block copolymers, i.e., Tetronic 304, 908, and 1107, with molecular masses ranging from 1,650 to 25,000 Da, were studied by monitoring in situ protein production at different time points after intramuscular (i.m.) injection of BLG-encoding plasmid DNA. Different doses of injected DNA were used (0.02, 1, and 50 μg). The adjuvant capacities of copolymers were evaluated using various criteria, such as primary specific antibody response and cytokine secretion after splenocyte reactivation. Lastly, we evaluated the effects of DNA immunization with the different copolymers and with the different plasmid doses on further allergic sensitization and challenge with BLG protein.     

A DSC study of the miscibility of poly(ethylene oxide)-block-poly(DL-lactide) copolymers with poly(DL-lactide).

The purpose of this study was to examine the miscibility of poly(ethylene oxide)-block-poly(DL-lactide) copolymers with poly (DL-lactide). The copolymers L7E73L7 and L17E78L17 (L = carbonyloxymethylmethylene unit, OCOCH(CH3); E = oxyethylene unit, OCH2CH2) were synthesised by non-catalysed anionic polymerisation and characterised by gel permeation chromatography and 13C NMR. Blends of each of the copolymers with poly(DL-lactide) with compositions over the range from 10 to 90 wt% copolymer were cast as thin films and examined by differential scanning calorimetry (DSC) to determine glass transition temperatures (Tg) and melting temperatures (Tm). The phase diagram showed a region of miscibility above the melting point of the copolymer in the system (approx. 35-40 degrees C). Within this region the system was glassy at low mass fractions of oxyethylene in the copolymer (wE < or = 0.1) and rubbery at higher mass fractions. Below Tm a mechanically compatible glassy blend existed at low wE whilst quenching of systems of higher wE led to phase separation, the biphasic region consisting of crystalline Em-sequences of copolymer separated from non-crystalline poly(DL-lactide). The phase diagram resulting from this study provides the means for the design of drug delivery systems based on blends of poly(DL-lactide) and poly(ethylene oxide)-containing components. The crystal melt boundary can be lowered by the use of block copolymers with short poly(ethylene oxide) blocks permitting the preparation of blends which are miscible at room temperature and rubbery or glassy according to composition.     

Wound dressing with sustained anti-microbial capability

Amphiphilic poly(ether ester amide) (PEEA) multiblock copolymers were synthesized by polycondensation in the melt from hydrophilic poly(ethylene glycol) (PEG), 1,4-dihydroxybutane and short bisester-bisamide blocks. These amide blocks were prepared by reaction of 1,4-diaminobutane with dimethyl adipate in the melt. A range of multiblock copolymers were prepared, with PEG contents varying from 23-66 wt %. The intrinsic viscosity of the PEEA polymers varied from 0.58-0.78. Differential scanning calorimetry showed melting transitions for the PEG blocks and for the amide-ester blocks, suggesting a phase separated structure. Both the melting temperature and the crystallinity of the hard amide-ester segments decreased with increasing PEG content of the polymers. The equilibrium swelling ratio in phosphate buffered saline (PBS) increased with increasing amount of PEG in the polymers and varied from 1.7 to 3.7, whereas the polymer that contained 66 wt % PEG was soluble in PBS. During incubation of PEEA films in PBS, weight loss and a continuous decrease in the resulting inherent polymer viscosity was observed. The rate of degradation increased with increasing PEG content. The composition of the remaining matrices did not change during degradation. A preliminary investigation of the protein release characteristics of these PEEA copolymers showed that release of the model protein lysozyme was proportional to the square root of time. The release rate was found to increase with increasing degree of swelling of the polymers.     

Phase diagram and structural study of polystyrene — poly(ethylene oxide) block copolymers, 1. Systems polystyrene/poly(ethylene oxide)/diethyl phthalate

By means of low angle X-ray scattering and differential scanning calorimetry, we have drawn the phase diagrams of poly(ethylene oxide)-polystyrene block copolymers in the presence of diethyl phthalate as a preferential solvent of polystyrene. Such systems exhibit two liquid-cristalline structures in terms of temperature and solvent concentration. At temperatures below about 50°C, a lamellar structure (LC) with crystallized poly(ethylene oxide) chains exists. Between 50 and about 170°C, we find a structure with melted poly(ethylene oxide) chains. Like for amorphous block copolymers, the type of the latter structure is governed by the copolymer composition. We have shown that in the LC structure, the poly(ethylene oxide) chains crystallize folding in two superposed layers, and we have studied the number of folds and the crystallinity of the poly(ethylene oxide) blocks as a function of solvent concentration, composition and rel. mol. mass of the copolymer, and of the crystallization temperature.