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Abstract: The proteolytic enzyme α-chymotrypsin selectively cleaves the amorphous regions of silk fibroin protein (SFP) and allows the crystalline regions to self-assemble into silk microgels (SMGs) at physiological temperature. These microgels consist of lamellar crystals in the micrometer scale, in contrast to the nanometer-scaled crystals in native silkworm fibers. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis and zeta potential results demonstrated that α-chymotrypsin utilized only the non-amorphous domains or segments of the heavy chain of SFP to form negatively charged SMGs. The SMGs were characterized in terms of size, charge, structure, morphology, crystallinity, swelling kinetics, water content and thermal properties. The results suggest that the present technique of preparing SMGs by α-chymotrypsin is simple and efficient, and that the prepared SMGs have useful features for studies related to biomaterial and pharmaceutical needs. This process is also an easy way to obtain the amorphous peptide chains for further study. [Copyright &y& Elsevier]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]