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Abstract: Several demonstrations of the effective biodegradation in soil of pro-oxidant activated polyethylene (PE) have been reported recently. Nevertheless a comprehensive understanding of the ultimate fate in the environment of the oxidized fragments of oxo-biodegradable polyethylene materials needs the extension of the studies to other natural environments and in particular to aqueous media (river, lake, brackish and marine waters) where accidental plastic littering and the resulting degraded fragments eventually may end up. In this respect, as part of our continuing activity in the area of oxo-biodegradable polymeric materials, in the present paper we wish to report on the results attained in an ongoing investigation on the biodegradation in a water medium of thermally pre-oxidized low density polyethylene (LDPE) film samples containing pro-oxidant additives. Thermally oxidized LDPE-film samples and corresponding acetone extractable fractions were submitted to the effect of microorganism flora present in river water. The effective biodegradation was assessed by monitoring the amount of CO2 developed over time in a respirometer apparatus. Levels of biodegradation up to 12 and 48% for the degraded fragments and corresponding fractions extracted with boiling acetone were detected on a 100-day time frame. [Copyright &y& Elsevier]

Abstract: Poly(vinyl alcohol) (PVA) is considered to be one of the very few vinyl polymers soluble in water and susceptible to biodegradation in aqueous media by specific microorganisms, implying oxidation of the carbon backbone followed by a random endocleavage of the polymer chains. The overall process does not appear to be appreciably affected by either degree of polymerization (DPn) or degree of hydrolysis (HD) of PVA at least in the 100–1000 and 80–100% ranges, respectively. In order to assess the effect of HD on the biodegradation propensity of PVA, different PVA samples having similar DPn and noticeably different HD values were synthesized by controlled acetylation of commercial PVA (HD=99%) and submitted to biodegradation tests in aqueous medium, mature compost and soil by using respirometric procedures. Re-acetylated PVA samples characterized by HD of between 25 and 75% underwent extensive mineralization when buried in solid media, whilst PVA (HD=99%) showed recalcitrance to biodegradation under those conditions. An opposite trend was indeed observed in aqueous solution, thus suggesting that biodegradation is not an absolute attribute directly related to structural features of the substrate under investigation. Boundary conditions related to the framework under which the biodegradation assessment is undertaken have to be taken into account and specifically well defined. [Copyright &y& Elsevier]

Thermally degradable low-density polyethylene samples containing TDPA™ pro-oxidant additives from EPI Inc. were submitted to an investigation aimed at evaluating their ultimate biodegradation (e.g. mineralization) in soil and mature compost incubation media. Respirometric tests aimed at simulating soil burial and composting (mature compost) conditions, were used for testing the potential biodegradability of polyolefins in the environment. An LDPE-TDPA film sample provided by EPI Inc. was also submitted to a thermal oxidative degradation treatment in order to mimic the thermophilic phase of a full scale composting process. Retrieved degradation specimens, their solvent extracts and residues were also tested in soil burial respirometric tests in order to evaluate their potential biodegradability. Original and test samples submitted to biotic environments were characterized by means of spectroscopic analysis. LDPE-TDPA sample replicates undergo biodegradation as mediated by soil microorganisms in respirometric experiments. High mineralization levels were observed, above 60%, comparable to those occurring in the case of several natural polymers in natural environments; the time for biodegradation, though, is relatively longer. However, it is clear from the positive biodegradation profile that biodegradation continues. The degradation process is accompanied by a dramatic change in the structural characteristics of the test samples. To the best of our knowledge, this is the first study clearly indicating the biodegradation and assimilation of a synthetic polyolefin at a substantial level, even though reached at fairly long incubation time. [Copyright &y& Elsevier]

Poly(vinyl alcohol) (PVA) is recognized as one of the very few vinyl polymers soluble in water also susceptible of ultimate biodegradation in the presence of suitably acclimated microorganisms. Accordingly, increasing attention is devoted to the preparation of environmentally compatible PVA-based materials for a wide range of applications. The present article is aimed at providing a survey of the available information on the environmental fate of PVA and PVA-based materials. Literature data and recent advances on the biochemistry and microbial physiology of PVA biodegradation and on the influence of environmental conditions are discussed along with the biodegradation processes of other water-soluble materials. The biodegradation behaviors of several PVA-based materials including blends, composites and copolymers are also reviewed and discussed. [Copyright &y& Elsevier]

Investigates the formulation of hybrid nanoparticles based on synthetic polymer-protein hybrid matrices for the release of proteic drugs with antiviral activity. Use of digalactosyl diacyl glycerol; Preparation of nanoparticle suspensions; Utilization of slow solvent evaporation.

Different types of multifunctional hydrophilic polymers were synthesized and characterized in view of their possible biomedical application. Several poly(amide)s and poly(ester-amide)s containing oligo(oxyethylene) segments and tartaric or succinic acid residues were prepared by activated polycondensation methods. New functional derivatives of β-cyclodextrin were obtained by reaction with glycidyl ether of protected polyols. The mechanism of β-cyclodextrin polymerization with epichlorohydrine was investigated by 13C-NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The utilization of silk fibroin protein (SFP) in the field of biomaterials and tissue engineering plays an important role due to its promising mechanical, biological, and processing properties. In the present study, SFP solutions were exposed to ultrasound sonication to assess impact on molecular weight (Mw), sol-gel transition behavior, and physico-chemical properties. The Mw of SFP was significantly reduced with sonication, determined by sodium dodecyl sulfate polyacrylamide gels (SDS-PAGE) gel electrophoresis. Sol-gel transitions were observed as SFP assembled to form a reversible SFP gel network at different concentrations and sonication time with the formation of a β-sheet-rich conformation in the gel state. The conformational changes and morphological properties were correlated over a range of SFP concentrations by circular dichroism (CD), UV spectroscopy, swelling and attenuated total reflectance fourier transformed infrared spectroscopy (ATR-FTIR). [ABSTRACT FROM AUTHOR]

The work presented here is aimed at suggesting plausible hypotheses for functional oligomeric forms of the human asialoglycoprotein receptor (ASGP-R), by applying a combination of different computational techniques. The functional ASGP-R is a hetero-oligomer, that comprises of several subunits of two different kinds (H1 and H2), which are highly homologous. Its stoichiometry is still unknown. An articulated step-wise modeling protocol was used in order to build the receptor model in a minimal oligomeric form, necessary for it to bind multi-antennary carbohydrate ligands. The ultimate target of the study is to contribute to increasing the knowledge of interactions between the human ASGP-R and carbohydrate ligands, at the molecular level, pertinent to applications in the field of hepatic tissue engineering. [ABSTRACT FROM AUTHOR]

Low-density polyethylene (LDPE) blended with poly(3-hydroxybutyrate) (PHB) and additivated with pro-oxidant were soil buried for 180 days and characterized using thermogravimetry (TG) and differential scanning calorimetry (DSC). TG data showed that both onset and maximum rate degradation temperatures decreased as a function of biodegradation time. Apparent activation energies ( Ea) using the Broido integral method decreased with the burial time increasing. PE crystallinity degree values increased in general up to 2 months of biodegradation. At the end of the soil burial (SB) test these values decreased principally for samples that were previously thermo-oxidized in an oven. [ABSTRACT FROM AUTHOR]

Abstract: Diallyl dimethyl ammonium chloride (DADMAC)-N-vinyl 2-pyrrolidinone (NVP) copolymers were demonstrated to provide excellent stabilities for in situ generated CdS nanoparticles in aqueous medium. Nearly transparent and stable CdS dispersions (up to 0.1M concentrations) were produced in 1% copolymer solutions. Experiments showed that, increasing DADMAC content induces greater stabilization. UV-visible spectroscopy, fluorescence spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for characterization of the stable nanoparticles. TEM images showed snake-like alignment of nonspherical CdS nanoparticles with 50–70nm of size, due to template effect of the cationically charged polymer. The CdS nanoparticles in aqueous medium showed reasonably high catalytic activities in photolysis of water, as inferred from hydrogen evolution measurements carried out in the absence and presence of noble metals, Pd and Pt. The highest hydrogen evolution rate (5.6mL per gram of CdS in min) was detected in the presence of Pt metal, while illuminating with mercury lamp (160W). [Copyright &y& Elsevier]

Whey permeate from dairy industry was hydrolyzed enzymatically to cleave its main carbon source, lactose, to glucose and galactose. The hydrolysis products were chosen as carbon sources for the production of poly-3-hydroxybutyric acid (PHB) by Pseudomonas hydrogenovora. In shaking flask experiments, the utilization of whey permeate as a cheap substrate was compared to the utilization of pure glucose and galactose for bacterial growth under balanced conditions as well as for the production of PHB under nitrogen limitation. After determination of the inhibition constant Ki for sodium valerate on biomass production (Ki =1.84g/l), the biosynthesis of PHA co-polyesters containing 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) units from hydrolyzed whey permeate and valerate was investigated. The application of hydrolyzed whey permeate turned out to be advantageous compared with the utilization of pure sugars. Therefore, fermentation under controlled conditions in a bioreactor was performed with hydrolyzed whey permeate to obtain detailed kinetic data (maximum specific growth rate, μ max =0.291/h, maximum polymer concentration, 1.27g/l PHB), values for molecular mass distribution (weight average molecular weight M w =353.5kDa, polydispersity index PDI=3.8) and thermo analytical data. The fermentation was repeated with co-feeding of valerate (maximum specific growth rate, μ max =0.201/h, maximum polymer concentration, 1.44g/l poly-(3HB-co-21%-3HV), weight average molecular weight M w =299.2kDa, polydispersity index PDI=4.3). [Copyright &y& Elsevier]

New chiral liquid-crystalline poly(vinylcyclopropane)s were prepared by free-radical ring-opening polymerization of the corresponding 2-vinylcyclopropane monomers. These side-group polymers had unconventional structures as they contained both linear and cyclic isomer repeat units. They formed an SmC phase around room temperature. General trends of the phase structures and transitions were found with the length of the spacer segment and the nature of the chiral substituent of the side-group mesogens. [ABSTRACT FROM AUTHOR]

The dependence of PVA biodegradation on polymer molecular weight, degree of hydrolysis, and content of head-to-head structural units was investigated in the presence of a PVA-degrading microbial population and of the relevant culture supernatant. Respirometric tests carried out in the presence of the selected microbial population evidenced a limited but significant delay in the mineralization profile depending upon the degree of PVA hydrolysis, whereas no remarkable effect by molecular weight was detected. Five bacterial strains were isolated from the PVA-degrading microbial population, but only the degradation of low molecular weight fractions was recorded in cultures inoculated with single bacterial strains. The exclusive attack of low molecular weight fractions is in accordance with the occurrence of an additional degradation mechanism different from that generally proposed for PVA biodegradation. Experiments carried out in the presence of the culture supernatant clearly demonstrated the presence of a PVA degrading enzymatic system in the solution. Kinetic studies carried out under the reported conditions suggested the occurrence of a random cleavage of PVA chains. No influence of both molecular weight and content of head-to-head structural units on the enzymatic degradation process was observed. Enzymatic assays excluded the presence of extracellular esterases in the culture supernatant but confirmed the presence of oxidases. [Copyright &y& Elsevier]

Presents a study which described the synthesis of graft and block copolymers by sequential cationic and free-radical polymerizations. Methodology; Results and discussion.

This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a microbiological shake flask experiment utilizing oxidized polypropylene (PP) waste as an additional carbon source. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust, and one of the best known producers of PHA. Making use of PHA oligomers, formed by controlled moderate-temperature degradation induced by carboxylate moieties, by examination of both the parent and fragmentation ions, the ESI-MS/MS analysis revealed the 3-hydroxybutyrate and randomly distributed 3-hydroxyvalerate as well as 3-hydroxyhexanoate repeat units. Thus, the bioconversion of PP solid waste to a value-added product such as PHA tert-polymer was demonstrated. [ABSTRACT FROM AUTHOR]

Two structurally isomeric homologous series of semiflexible thermotropic liquid crystalline polyesters were analysed by dielectric spectroscopy in temperature intervals varying from 253 to 403 K. Each series is characterised by a well-distinct behaviour of the dielectric loss versus temperature with a minor diffuse and a more confined relaxation occurring at lower and higher temperatures, respectively. Extrapolations from semilog plots of frequency ( f) versus reciprocal absolute temperature (1/ T) indicated that the principal relaxation is related to the glass transition temperature as defined by DSC. The analysis of data according to WLF equation indicated that the size and the kind of the polymethylene groups influence the apparent activation energy. A parity effect, connected to the length of polymethylene segments within each series, was finally detected on the relative position of the maximum relaxation, the odd numbers showing in any case higher temperature values. [ABSTRACT FROM AUTHOR]

The comparative behaviour to degradation of polypropylene (PP) films with 1 and 3 wt.% of experimental (transition metal free) and commercial (transition metal containing) pro-oxidant/pro-degradant additive were investigated under accelerated environmental conditions. Specimens of 20 μm films, obtained by extrusion of the samples of PP containing the pro-oxidant/pro-degradant additives, were initially exposed to irradiation in a UV chamber for 270 h, and then submitted to a degradation test in aqueous medium for 100 days. The CO 2 production in response of a microbial attack was monitored by back titration during all the experimented trials. The PP crystallinity was evaluated by differential scanning calorimetry (DSC) and the oxidation level was determined by the determination of carbonyl index by Fourier Transform Infrared analysis (FT-IR). The surface morphology of the PP samples was investigated by scanning electron microscopy. A degradation evidence of the additivated PP samples was attained in comparison with the behaviour of neat PP samples. The surface of the additivated PP films showed grooves and holes as a clear indication of the physical-chemical degradation. The PP samples with the experimental metal-free pro-oxidant/pro-degradant experienced a higher level of degradation with respect to the PP sample loaded with the commercial transition metal containing pro-oxidant/pro-degradant. Thus, the benzoin/potassium salt free of transition metal suggested in this work has showed be highly efficient degradant additive for PP degradation. [ABSTRACT FROM AUTHOR]

Objective(s): Despite of wide range applications of polymeric nanoparticles in protein delivery, there are some problems for the field of protein entrapment, initial burst and controlled release profile. Materials and Methods: In this study, we investigated the influence of some changes in PLGA nanoparticles formulation to improve the initial and controlled release profile. Selected parameters were: pluronic F127, polysorbate 80 as surfactant, pH of inner aqueous phase, L/G ratio of PLGA polymer, volume of inner aqueous phase and addition of polyvinylpyrrolidone as an excipient. FITC-HSA was used as a model hydrophilic drug. The nanoparticles were prepared by nanoprecipitation. Results: Initial release of FITC-HSA from PLGA-tween 80 nanoparticles (opt-4, 61%) was faster than control (PLGA-pluronic) after 2.30 h of incubation. Results showed that decrease in pH of inner aqueous phase to pI of protein can decrease IBR but the release profile of protein is the same as control. Release profile with three phases including a) initial burst b) plateau and c) final release phase was observed when we changed volume of inner aqueous phase and L/G ratio in formulation. Co-entrapment of HSA with PVP and pluronic reduced the IBR and controlled release profile in opt-19. Encapsulation efficiency was more than 97% and nanoparticles size and zeta potentials were mono-modal and -18.99 mV, respectively. Conclusion: In this research, we optimized a process for preparation of PLGA-PVP-pluronic nanoparticles of diameter less than 300 nm using nanoprecipitation method. This formulation showed a decreased initial burst and long lasting controlled release profile for FITC-HSA as a model drug for proteins. [ABSTRACT FROM AUTHOR]

Poly(ester-ether-urethane)s copolymers are a resourceful class of biopolymers for the preparation of nanocarriers for drug delivery applications. However, a simple clinical translation for this synthetic material with biological and quality features is still needed. In this view, poly(ε-caprolactone)- co -poly(ethylene glycol) copolymers were synthesized as semi-bulk pilot (Kg) scale under mild conditions in absence of catalyst, bearing functional termini such as fluorescein tag and anticancer targeting moieties. The obtained materials were processed into surface decorated paclitaxel (PTX) loaded nanoparticles (NPs). The NPs were fully characterized in vitro and in vivo biodistribution in healthy mice evidenced no sign of toxicity and lower levels of PTX in lung and spleen, compared to clinically applied PTX dosage form. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) with tailored properties are needed to meet consumer demands regarding the use of eco-compatible biobased polymeric materials and relevant plastic items. Inserting 3-hydroxvalerate (3HV) monomeric units in PHA biopolyesters results in poly[( R)-3-hydroxybutyrate- co-( R)-3-hydroxyvalerate] (PHBHV) copolyesters aimed at their conversion into production of biodegradable eco-friendly plastic items. As inexpensive novel precursor substrate structurally related to 3HV, a mixture of odd-numbered carboxylic acids with 9-17 carbon atoms was produced by oxidative ozonolysis of alkenes. This mixture was successfully applied for biomediated PHBHV production by Cupriavidus necator. Applying this mixture as carbon substrate, a molar 3HV fraction exceeding 0.12 was obtained. The isolated copolyesters featured a low degree of crystallinity, narrow molar mass distribution, and low melting temperatures. These properties should make application of the novel 3HV-precursors interesting for large-scale production of easily processable copolyesters. [ABSTRACT FROM AUTHOR]

In the present paper we report the exclusive microbial preparation of polyhydroxyalkanoates (PHA) containing 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV) and 4-hydroxybutyrate (4HB) as comonomers through the use of unexpensive carbon sources such as whey from dairy industry. Polymers were produced by growing H. pseudoflava DSM 1034 in minimal medium supplemented with sucrose, lactose or whey without any co-substrate added. The chemical and physical properties of the polymers were fully characterized by GPC, DSC, TGA analyses and the composition by GC and 1H NMR examinations to especially confirm the content of different monomeric units. The presence of 4HB units into PHA samples is particularly aimed in thermoplastic applications where greater flexibility is required and conventional rigid PHAs tend to fail. Usually the insertion of 4HB into chain backbone consisting of 3-hydroxyalkanoates requires expensive carbon sources mostly of petrochemical origin. According to our study the production of P(3HB-co-3HV-co-4HB) terpolymer can be obtained directly by the use of lactose or waste raw materials such as cheese whey as carbon sources. Although the amount of 4HB in the produced terpolymers was usually low and not exceeding 10% of the total molar composition, a PHA containing 18.4% of 4HB units was produced in 1 step fermentation process from this structurally unrelated carbon sources. The crystallinity of the terpolymer is basically to be markedly affected with respect to that of conventional PHAs, thus obtaining a comparatively less rigid material and easier to be processed. [ABSTRACT FROM AUTHOR]

Highlights: [•] PLA nanocomposites incorporating neat BCNW and PGMA-grafted BCNW were produced and characterized. [•] PGMA grafting enhanced the adhesion between PLA and BCNW. [•] BCNW improved the oxygen barrier of PLA, especially at low relative humidity. [•] PGMA-grafted BCNW presented lower moisture sensitivity than neat BCNW. [•] Nanocomposites loaded with PGMA-grafted BCNW preserved the ductility of neat PLA. [ABSTRACT FROM AUTHOR]

A novel triblock copolymer PS-PHB-PS based on the microbial polyester Poly[( R)-3-hydroxybutyrate)] (PHB) and poly(styrene) (PS) was prepared to be used as compatibilizer for the corresponding PHB/PS blends. It was prepared in a three-step procedure consisting of (i) transesterification reaction between ethylene glycol and a high-molecular-weight PHB, (ii) synthesis of bromo-terminated PHB macroinitiator, and (iii) atom transfer radical polymerization polymerization of styrene initiated by the PHB-based macroinitiator. Fourier transform infrared, gel permeation chromatography, 1H-, and 13C-NMR spectroscopies were used to determine the molecular structure and/or end-group functionalities at each step of the procedure. Although thermogravimetric analysis showed that the block copolymer underwent a stepwise thermal degradation and had better thermal stability than their respective homopolymers, differential scanning calorimetry displayed that the PHB block in the copolymer could not crystallize, and thus generating a total amorphous structure. Atomic force microscopy images indicated that the block copolymer was phase segregated in a well-defined morphological structure with nanodomain size of ∼40 nm. Contact angle measurements proved that the wettability properties of the block copolymer were in between those of the PHB and PS homopolymers. Blends analyzed for their morphology and thermal properties showed good miscibility and had well-defined morphological features. Polymer blends exhibited lower crystallinity and decreased stiffness which was proportional to the amount of compatibilizer content in the blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Abstract: A blend of poly(lactic acid) (PLA) (75% by weight) and poly(3-hydroxybutyrate) (PHB) (25% by weight) with a polyester plasticizer (Lapol 108) at two different concentrations (5 and 7% by weight per 100 parts of the blends) were investigated by TGA, DSC, XRD, SEM, mechanical testing and biodegradation studies. PLA/PHB blends showed a good distribution of the major components and absence of phase separation. XRD showed that the original crystal structure of PHB in the PLA75/PHB25 blend had been disturbed. DSC curves of PLA or PHB with plasticizer exhibited one T g value, indicating that both major blend components are miscible. The T g values also decreased with increased amount of plasticizer and showed good correlation to the Fox Equation, The melting temperature of PLA and PHB blends mostly did not change with an increase in plasticizer content, and the thermal stability of PLA and PHB was not affected. Also, the elongation at break of the PLA/PHB blend was greatly improved with the addition of plasticizer. In addition, in preliminary biodegradation studies carried in natural compost neat PHB showed some biodegradation, whereas the samples containing PLA did not experience a substantial biodegradation. This last aspect is worthy of further investigation in a more comprehensive and detailed approach. [Copyright &y& Elsevier]

An electrospinning procedure allowing the spinning of a straight jet of polymer solution was developed. By using proper collector devices, it enables to collect winded and aligned fibers and to prepare polymeric constructs developing along the Z axis. The reported results are expected to provide basic understandings on which parameters are controlling the stability/instability of the process and implement new applications of electrospinning with specific reference to the preparation of well defined three-dimensional structures. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the study is to elucidate the effect of reaction temperature and time during heterogeneous alkali reaction on degree of deacetylation (DD) of chitin. Two different analytical methods namely 1st derivative ultraviolet and Fourier transform infrared spectroscopies have been adopted to determine and compare the DD values of the prepared chitin derivates. Statistical analysis indicates that the most significant variable is the temperature followed by the time with slight interdependence between the two. By applying the developed statistical model, using temperature and time as the process variables, chitosan with 80% DD can be obtained in 9h using 50% (v/v) NaOH and a reaction temperature of 100°C. Thermal analysis both in air and nitrogen showed that thermodegradation occurs in two steps in the 200–600°C range. The 1st derivative ultraviolet method has been advocated as a suitable method for the assessment of chitin derivates. [Copyright &y& Elsevier]

The ultimate aim of this study is to identify new molecules that are able to recognize polymerized fibrin, which is the main component of a thrombus. These selective ligands can be exposed on the surface of particular nanoparticles used for the targeted delivery of fibrinolytic drugs. The targeted delivery of these drugs is expected to help to keep under control the severe side effects which can occur if the drugs are administered systemically. The study focuses on the application of high-throughput docking methods used to screen a library of thousands of commercial compounds. The aim was to identify molecules that are potentially capable of interacting with the human fibrin γ(312-324) epitope. The best scoring compounds were purchased and tested through fluorimetric assays in order to estimate their affinity toward fibrin. The results show that the protocol proposed here for identifying new compounds of interest may provide a valuable contribution to the discovery of lead molecules for human fibrin recognition. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Poly(hydroxyalkanoates) (PHAs) constitute biodegradable polyesters and are considered among the most promising candidates to replace common petrochemical plastics in various applications. To date, all commercial processes for PHA production employ microbial discontinuous fed-batch fermentations. These processes feature drawbacks such as varying product quality and the inevitable periods of downtime for preparation and post-treatment of the bioreactor equipment. An unprecedented approach to PHA production was chosen in the presented work using a multistage system consisting of five continuous stirred tank reactors in series (5-SCR), which can be considered as a process engineering substitute of a continuous tubular plug flow reactor. The first stage of the reactor cascade is the site of balanced bacterial growth; thereafter, the fermentation broth is continuously fed from the first into the subsequent reactors, where PHA accumulation takes place under nitrogen-limiting conditions. Cupriavidus necator was used as production strain. The focus of the experimental work was devoted to the development of a PHA production process characterized by high productivity and high intracellular polymer content. The results of the experimental work with the reactor cascade demonstrated its potential in terms of volumetric and specific productivity (1.85 g L h and 0.100 g g h, respectively), polymer content (77%, w/ w) and polymer properties ( M = 665 kg/mol, PDI = 2.6). Thus, implementing the technology for 5-SCR production of PHB results in an economically viable process. The study compares the outcome of the work with literature data from continuous two-stage PHA production and industrial PHA production in fed-batch mode. [ABSTRACT FROM AUTHOR]

Biodegradable amphiphilic multiblock poly(ether-ester-urethane)s were prepared by one-step bulk polycondensation of PEG and PCL macrodiols and HMDI with good yields and high molecular weights. The copolymers were characterized by 1H-NMR, FT-IR, SEC, TGA and DSC analysis. Different ratios of PEG/PCL, PEG macromonomer length and copolymer molecular weights allowed for tuning their hydrophilicity. Thanks to their tunable characteristics, the prepared multiblock copolymers can be exploited in the fabrication of biodegradable scaffolds for tissue engineering by means of the electrospinning technique. [ABSTRACT FROM AUTHOR]

Fibrous meshes based on three different poly(vinyl alcohol) (PVA) polymers, with 12% vinyl acetate monomeric units and molar weights of 37,000, 67,000, and 130,000 were developed as potential scaffolds for regenerative medical applications. The meshes were electrospun and characterized by molecular weight, concentration, applied voltage, and needle—collector distance. The influence of feed rate and the electrodes configuration (needle-to-tip and screen-to-screen system) was determined. Highly porous, 3D structures composed of randomly oriented ultrafine fibers, with an average fiber diameter of a few hundred nanometers were developed. Solutions of PVA and human serum albumin were successfully electrospun and the fibrous mesh was stabilized with glutaraldehyde. The influence of these operations on the mechanical properties was evaluated by uniaxial tensile testing. [ABSTRACT FROM AUTHOR]

Abstract: Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation on the oxidation and biodegradation of linear low density poly(ethylene) PE-LLD films containing pro-oxidant were examined. To achieve oxidation and degradation, films were first exposed to the sunlight for 93 days during the summer months followed by their incubation with fungal strains previously isolated from the soil based on the ability to grow on the oxidized PE-LLD as a sole carbon source. Some films were also thermally aged at temperatures ranging between 45°C and 65 °C, either before or after fungal degradation. Films with pro-oxidant additives exhibited a higher level of oxidation as revealed by increase in their carbonyl index (COi). In addition to increase in the COi, films showed a slight increase in crystallinity and melting temperature (T m), considerably lower onset degradation temperatures, and a concomitant increase in the % weight of the residues. The level of oxidation observed in thermally aged films was directly proportional to the aging temperature. The PE-LLD films with pro-oxidant exposed to sunlight followed by thermal aging showed even higher rate and extent of oxidation when subsequently subjected to fungal biodegradation. The higher oxidation rate also correlated well with the CO2 production in the fungal biodegradation tests. Similar films oxidized and aged but not exposed to fungal biodegradation showed much less degradation. Microscopic examination showed a profuse growth and colonization of fungal mycelia on the oxidized films by one strain, while another spore-producing strain grew around the film edges. Data presented here suggest that abiotic oxidation of polymer''s carbon backbone produced metabolites which supported metabolic activities in fungal cells leading to further biotically-mediated polymer degradation. Thus, a combined impact of abiotic and biotic factors promoted the oxidation/biodegradation of PE-LLD films containing pro-oxidants. [Copyright &y& Elsevier]

In the present study polymeric membranes consisting of poly(vinyl alcohol) (PVA) and multi-walled carbon nanotubes (MWCNTs) were prepared by casting method and their morphological, thermal and de-swelling behaviour were characterized. The effect of MWCNTs in the hybrid membranes was more significant when its concentration was high. The thermo degradation ( Td) and crystallization ( Tc) temperatures of PVA increased of 10 and 9 °C, respectively in presence of 50 × 10−2 w v−1% of MWCNTs (PVNT3). Besides, the amount of non-free water increases with increasing of MWCNTs probably due to a capillary effect. [ABSTRACT FROM AUTHOR]

Abstract: Fibrin represents a suitable target for addressing delivery systems loaded by fibrinolytic drugs. Selective ligands capable to recognize fibrin could be used as targeting moieties for such systems. In this study the interactions between the γ(312–324) epitope of human fibrin and peptidic ligands were analyzed by using experimental and computational methods. Binding free energies were calculated through the molecular mechanics/generalized born surface area approach. Good qualitative agreements between the experimental and calculated data were obtained. The binding affinity seems to be well correlated (R 2 =0.69) with the changes of the nonpolar solvation energy term computed from solvent-accessible surface area calculation. These results indicate that current methods of estimating binding free energies are efficient for achieving information on protein–ligand interactions. [Copyright &y& Elsevier]

Amphiphilic copolymers are appealing materials because of their interesting architecture and tunable properties. In view of their application in the biomedical field, the preparation of these materials should avoid the use of toxic compounds as catalysts. Therefore, enzymatic catalysis is a suitable alternative to common synthetic routes. Pentablock copolymers (CUC) were synthesized with high yields by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by Pluronic (EPE) and catalyzed by Candida antarctica lipase B enzyme. The variables to study the structure–property relationship were EPEs' molecular weight and molar ratios between ε-CL monomer and EPE macro-initiator (M/In). The obtained copolymers were chemically characterized, the molecular weight determined, and morphologies evaluated. The results suggest an interaction between the reaction time and M/In variables. There was a correlation between the differential scanning calorimetry data with those of X-ray diffraction (WAXD). The length of the central block of CUC copolymers may have an important role in the crystal formation. WAXD analyses indicated that a micro-phase separation takes place in all the prepared copolymers. Preliminary cytotoxicity experiments on the extracts of the polymer confirmed that these materials are nontoxic. [ABSTRACT FROM AUTHOR]

Poly (hydroxyalkanoates) (PHAs) have recently attracted a great deal of academic and industrial interest for their biodegradability and biocompatibility making them suitable for environmental and biomedical applications. Poly(3-hydroxybutyrate-) (PHB-) and Poly(DL-lactide-co-glycolide) (PLGA-) based nanoparticles were prepared using the dialysis method as yet unreported for the preparation of nanoparticles based on PHB. Processing conditions were varied in order to evaluate their influence on morphology, drug encapsulation, and size of nanoparticles. The relevant results obtained give a theoretical understanding of the phenomenon occurring during colloidal formation. The adopted procedure allows for a relatively small diameter and homogeneity in size distribution of the PHB nanoparticles to be obtained compared to other methods like the one based on solvent evaporation which leads to particles on microscale. The biocompatibility of PHB and relative nanoparticles was investigated and both exhibited very good cytocompatibility. [ABSTRACT FROM AUTHOR]

Abstract: This article reports on the current status of the research on blood substitutes with particular attention on hemoglobin-based oxygen carriers (HBOCs). Insights on the physiological role of hemoglobin are reported in the view of the development of both acellular and cellular hemoglobin-based oxygen carriers. Attention is then focused on biocompatible polymeric materials that find application as matrices for cellular based HBOCs and on the strategies employed to avoid methemoglobin formation. Results are reported regarding the use of bioerodible polymeric matrices based on hemiesters of alternating copolymer (maleic anhydride-co-butyl vinyl ether) for the preparation of hemoglobin loaded nanoparticles. [Copyright &y& Elsevier]

Abstract: The preparation of novel biocompatible polymeric nanoconstructs suitable to load sensitive bioactive protein agents is reported. Nanoparticles were prepared as based on hybrid polymeric matrices consisting of synthetic bioerodible alternating copolymers of maleic anhydride and n-butylvinylether hemiesterified with 2-methoxyethanol and grafted with poly(ethylene glycol) segments and monoclonal antibody single chain fragment specific for fibrin clot. The prepared nanoparticles were loaded with proteolytic enzymes (trypsin and urokinase), encapsulating up to 2500UI of urokinase/mg of dried nanoparticles. The release of the enzyme from nanoparticles resulted time controlled and it was assessed that in case of administration of urokinase-loaded nanoparticles, the enzyme would preserve its thrombolytic properties more efficiently in respect to free drug administration. Moreover, the nanoparticles showed a good in vitro biocompatibility, suitable for biomedical applications. The stability (shelf life) of the prepared nanostructured dosage forms was evaluated. The drug-loaded nanoparticles resulted stable under stressed conditions (35°C for 13 weeks) in a lyophilized form and preserved their morphological and functional characteristics when stored in suspension for 18 months at 4°C. [Copyright &y& Elsevier]

This is a study of the in vitro cytotoxicity and intracellular fate of poly[(glycylglycinemethacrylamide)-co-N-(2-hydroxypropylmethacrylamidey)] bio-eliminable polymer samples and relative nanoparticles in BalbIc 3T3 cloned A31 mouse embryo fibroblasts cell line by using Confocal Laser Scanning Microscopy (CLSM). Nanoparticles were prepared by co-precipitating the polymers with fluorescein labeled human serum albumin (HSA-FITC) as the fluorescent probe and as the model protein drug. The toxicity of the polymers containing 25, 50 and 100%, respectively, of (glycylglycinemethacrylamide)! (GGMA) was investigated in terms of cytoskeleton morphology by exposing cells to various concentrations of polymers for 24 h. Under normal culture conditions, fibroblast cells exhibit characteristic spreading and shape, however, when the cell cultures were subjected to chemical, metabolic or physical stress, their morphology changed reducing their visibility. The polymers with the lower glycine content exert a lower toxicity even at high concentrations [8.5 mg/mL]. The cellular uptake of nanoparticles was determined by incubating fibroblasts with HSA-FITC loaded particles and HSA-FITC alone at three different time points. The results indicate that nanoparticles were up-taken by the cells in a time dependent fashion. Preliminary evaluation of the intracellular fate of the prepared nanoparticles indicate their possible lysosomal escape. [ABSTRACT FROM AUTHOR]

Abstract: Telechelic N-vinyl-2-pyrrolidinone (NVP) oligomers terminated by hydroxyl groups were prepared by radical polymerization in the presence of functional chain transfer agents. Then hydroxy-terminated poly(NVP) was used as initiator in the ring opening polymerization of ε-caprolactone (ε-CL). Experiments were performed either under basic conditions or by using SnOct2 or ZnEt2 as catalyst. The resulting amphiphilic AB-type block copolymers were thoroughly characterized by spectroscopic and thermal techniques. These data and fractionation in protic solvents indicated that the copolymerization products are constituted by a mixture of copolymers with a wide composition range. The water-soluble copolymer fractions formed micelles and nanoaggregates that showed an appreciable capacity of loading piroxicam, a hydrophobic non-steroidal anti-inflammatory drug. Contact angle measurements, atomic force microscopy, and surface plasmon resonance measurements indicated that the surface of films prepared from the insoluble fractions does not have antiopsonizing properties in spite of their high hydrophilicity. [Copyright &y& Elsevier]

Abstract: Environmentally degradable polymers and plastics (EDPs) are a group of polymeric materials experiencing a rapid growth in number as well as in their applications and quantities used. The assessment of their key characteristic – degradability, including eventually biodegradability as the ultimate stage, is scientifically and technically a challenging issue and has led to differing interpretations in the past. In order to standardize techniques and criteria a number of standards were established by different standardization bodies which are also used as a basis for certification schemes. An up-to-date inventory of the rapidly growing standardization body is presented with basic interpretation to help guide the non-expert. A basic introduction to EDPs and polymer degradation is added for clarity. [Copyright &y& Elsevier]

Molecular simulation techniques are used to explore and characterize the atomic scale structure, and to predict binding energies and basal spacing of polymer/clay nanocomposites based on polypropylene (PP) and maleated polypropylene (PPMA), montmorillonite (MMT), and different alkylammonium ions (quats) as surfactants. Our evidences suggest that shorter hydrocarbonic chains are more effective in producing favorable binding energies with respect to longer ones, and the substitutions of hydrogen atoms with polar groups on the quaternary ammonium salt (quat) generally results in greater interaction between quat and both polymer and clay. Under the hypothesis, that montmorillonite platelets are uniformly dispersed in a polymer matrix, the modified polypropylene yields higher interfacial strength with clay than neat polypropylene. The use of neat PP and quats with higher molecular volume offer the higher values of the basal spacing and thus, in principle, they should be more effective in the exfoliation process. [Copyright &y& Elsevier]

The work presented here is aimed at designing high-affinity ligands for the fibrin γ(312–324) epitope. This epitope is specific for fibrin recognition, as it is exposed only on the fibrin surface, while in fibrinogen it is buried in the protein bulk. This property makes it very useful for therapeutic applications. In fact, it may be exploited in driving systems for targeted delivery of thrombolytic drugs toward the specific compartment where they are needed. It will then allow avoidance of serious unwanted side effects produced by a conventional systemic administration. The approach chosen for designing putative ligands is based on the known three-dimensional (3D) structure of the epitope. A wide virtual library made up of oligo-peptides and analogues designed by a combinatorial approach, on the basis of chemical complementarity criteria, has been screened by means of a docking/scoring approach (DOCK program). The peculiarity of the problem under study required a considerable effort in finding a method enabling the experimental validation of the design work results. In fact the selected biological target is absolutely new, so that neither a endogenous, nor a synthetic high-affinity ligand is known up to now. It does not allow for the validation of computational results by means of classical binding tests based on the use of known labeled high-affinity ligands. Preliminary binding essayes were so carried out by means of the Plasmon Surface Resonance (PSR) technique. The experimental results suggested that most of the molecules predicted to be good ligands by means of the selected computational tools, could carry the wanted affinity toward the selected target. [ABSTRACT FROM AUTHOR]

Different samples of aminated latex of poly(styrene-co-Boc-aminostyrene) microspheres with mean diameters varying from 0.7 to 1.0 μm were prepared by dispersion copolymerization of styrene (ST) and Boc-aminostyrene (Boc-AMST). The copolymer compositions determined by nuclear magnetic resonance (1H NMR) were Boc-AMST/ST 6.9/93.1 mol/mol % (BOC7 sample) and Boc-AMST/ST 31.3/68.7 mol/mol % (BOC30 sample). The average molecular weights determined by gel permeation chromatography were 126 kDa (BOC7 sample) and 51 kDa (BOC30 sample). The latex containing NH-carbo-tert-butoxy groups (NH-Boc) were treated with 2 M HCl in isopropyl alcohol/water (1:1 vol/vol), at 50 °C for 3, 6, 9, 24, and 30 h, in order to control the extent of deprotection reaction of the NH-Boc. The deprotection reaction resulted in the formation of NH+3Cl− groups on the particle surfaces. The kinetic of the deprotection reaction was investigated by 1H NMR analyses and the yield varied from 20 to 40%. The resulting &z.sbnd;NH+3Cl− groups on the microsphere surfaces were examined, in particular, by electron spectroscopy imaging (ESI) using an energy-filtered transmission electron microscope (EFTEM) that clearly demonstrated the presence of Cl on the particle surfaces. Scanning electron photomicrographs recorded for the above samples showed that the particle morphology was maintained after the acidic treatment. [Copyright &y& Elsevier]

The photon transmission technique was used to study the phase transitions of a liquid crystalline acrylate monomer, 6-(4-cyanobiphenyl-4′oxy)hexyl acrylate (LC6), its homopolymer (PLC6) and its graft copolymer (GLC6) with polytetrahydrofuran grafts. The phase transitions were also confirmed by DSC and polarizing microscopy. We observed the phase transition sequence isotropic-nematic-smectic A-smectic C in the LC6 monomer. In PLC6 and GLC6 polymers, the nematic and smectic A phases appear dominant. The apparent nematic-smectic A transition is of first order in PLC6 and of second order in GLC6, with the transition temperature remaining the same. The effects of quenched random constraints introduced in GLC6 are consistent with the theory of quenched random interactions. The critical exponents were also evaluated. [ABSTRACT FROM AUTHOR]

A procedure for the preparation of (S)-dolichol and (S)-nordolichol starting from the polyprenyl fraction extracted from Gingko Biloba integer or extracted leaves is described. Two chiral isoprenoid compounds in good yields and high degree of enantiomeric excess were obtained. The (S)-nordolichol appears to be a good chiral precursor for the preparation of [sup 14]C-labeled (S)-dolichol which is to be used in investigations aimed at gaining further information with respect to the role of dolichol in the function of living cells. KEY WORDS: dolichol; nordolichol; polyprenols; Gingko Biloba leaves. [ABSTRACT FROM AUTHOR]

Poly(B-thioesters) were synthesized by Michael-type base-catalyzed polyaddition of oligo(ethylene glycol) A,O-dithiols to bis(acrylic esters). Fine tuning of the hydrophilic--hydrophobic balance of the polymers can be achieved by modulating the length of the oligo(ethylene glycol) segment and the nature of the spacer between the two ester groups in the bis(acrylate) moiety. Investigation of the reactivity of oligo(ethylene glycol)dithiols with acrylic systems is reported, with the aim of determining the best conditions for a polyaddition process involving the base catalyzed addition of such dithiols to bis(acrylate) systems. Some hypotheses are proposed for the role of the solvent and of the catalyst. The influence of the molecular structure of the reactants on reactivity and on the properties of the resulting polymers is also discussed. [ABSTRACT FROM AUTHOR]

Two new families of chiral monomers were synthesized which consisted of a spaced biphenyl core and a 2,3-disubstituted or 2,2-disubstituted oxirane ring. The former monomers formed liquid crystal mesophases, whereas the latter monomers did not generate any mesophases independent of the spacer lengths investigated. The mesogenic propensity was enhanced in chiral liquid crystals based on the biphenyl benzoate core and either oxirane ring. A linear electro-optic response was detected in the chiral nematic phase and was attributed to the flexoelectric effect. [ABSTRACT FROM AUTHOR]

Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance of potential carbon sources with huge economic value being neglected. These waste plastics, through biological fermentation, could offer alternatives to traditional petrol-based plastics. Polyhydroxyalkanoates (PHAs) are a group of plastics produced by some strains of bacteria that could be part of a new generation of polyester materials that are biodegradable, biocompatible, and, most importantly, non-toxic if discarded. This study introduces the use of prodegraded high impact and general polystyrene (PS0). Polystyrene is commonly used in disposable cutlery, CD cases, trays, and packaging. Despite these applications, some forms of polystyrene PS remain financially and environmentally expensive to send to landfills. The prodegraded PS0 waste plastics used were broken down at varied high temperatures while exposed to ozone. These variables produced PS flakes (PS1–3) and a powder (PS4) with individual acid numbers. Consequently, after fermentation, different PHAs and amounts of biomass were produced. The bacterial strain, Cupriavidus necator H16, was selected for this study due to its well-documented genetic profile, stability, robustness, and ability to produce PHAs at relatively low temperatures. The accumulation of PHAs varied from 39% for prodegraded PS0 in nitrogen rich media to 48% (w/w) of dry biomass with the treated PS. The polymers extracted from biomass were analyzed using nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) to assess their molecular structure and properties. In conclusion, the PS0–3 specimens were shown to be the most promising carbon sources for PHA biosynthesis; with 3-hydroxybutyrate and up to 12 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units generated. [ABSTRACT FROM AUTHOR]