Can Polyethylene be a Photo(bio)Degradable Synthetic Polymer?

Abstract

A polymeric system based on LDPE would be qualified as a “photo(bio)degradable synthetic polymer” for use as films or thin systems in plasticulture and later in packaging where severe specific criteria should be respected. The evolution of such a system in environmental conditions should present three phases. In Phase I, corresponding to storage and use, in the presence of physicochemical and biological aggression, chemical evolution should be very limited and resistance to any microorganism should be observed. In Phase II a rapid abiotic degradation should occur until the complete destruction of physical (mechanical) properties and spontaneous fragmentation of the thin systems into more and more divided parts. Phase III corresponds to bioassimilation of heavily transformed (oxidized) solid particles. Phase I should be predicted and controlled on the basis of artificial photoaging or thermoaging experiments. Depending on the desired lifetime of the system, nonaccelerated, accelerated, or ultra-accelerated photoaging techniques could be used. The earliest fragmentation, which should be observed in Phase II, should be predicted within the same experiment. The prediction of the long-term fate of the polymeric materials should be based not only on the variations of physical properties but on a full analysis of the chemical evolution, i.e., determination of the major final transformed groups of the macromolecular chains (and especially the acidic end groups) and the molar mass distribution. In a recent BRITE-EURAM European contract, we developed an experimental protocol for the control of Phase III based on the use of pure cultures of strains from collections or selected adapted wild strains (from industrial polyethylene site dumpings) which had been examined. Abiotically oxidized LDPE was the only carbon source in a starving mineral medium. Bioerodibility caused by the carboxylic acid formed throughout abiotic degradation has been observed.     

Novel flower-like Sn–Cu and cactus-like Sn–Ag nanocatalysts for photo catalytically removal of toxic pollutant

In this study, dendrite-like Sn nanocomposites were achieved by engineering the synthesis parameters. The dendritic Sn nanostructures show higher photocatalytic activity compared to nanoplate Sn and hierarchical Sn nanostructures. Flower-like Sn–Cu and cactus-like Sn–Ag nanostructures were prepared to improve the photocatalytic activity of Sn nanostructures. Adding Cu and Ag improved the photocatalytic activity of Sn by 24% and 46%, respectively. The photodegradation results revealed that the cactus-like Sn–Ag has a high degradation rate (5.3 × 10⁻⁴ mmol L⁻¹ min⁻¹) compared to the Sn nanostructures (2.9 × 10⁻⁴ mmol L⁻¹ min⁻¹). This work provides new insight into the design of highly efficient photocatalysts by engineering the morphology.     

Excellent photocatalytic reduction of nitroarenes to aminoarenes by BiVO4 nanoparticles grafted on reduced graphene oxide (rGO/BiVO4)

A novel heterogeneous composite material based on reduced graphene oxide (rGO) and bismuth vanadate (BiVO₄) was prepared and characterized by various techniques such as powder XRD, HRTEM, EADX, UV–Vis‐DRS, FT‐IR, Raman, BET and XPS analyses. The characterization results reveal that the rGO well decorated by BiVO₄. The electrochemical impedance spectroscopy (EIS) shows the increasing of charge transfer of rGO/BiVO₄ in presence of light irradiation. In this research, the pure BiVO₄ and rGO/BiVO₄ composite have been explored for photocatalytic reduction of nitroarenes. Among the prepared nanocomposites, rGO loaded with 10% BiVO₄ catalyst (noted as rGO/BiVO₄–10%) shows the best performance for the photo‐reduction of various nitroaromatic molecules to their corresponding amine compounds under visible‐light irradiation at room temperature. The catalyst exhibited in particular excellent photocatalytic activity for the conversion of 1,4‐dinitrobenzene to 4‐nitroanilline (100% conversion) in 20 min, 4‐chloronitrobenzene to 4‐chloroaniline and 2‐nitrophenol to 2‐aminophenol (100% conversion) in only 30 min. In addition, the conversion of 4‐bromonitrobenzene, 4‐iodonitrobenzene to their corresponding amine compounds (100% conversion) was achieved in 60 min. The catalyst was recovered for several times and reused without decreasing of its efficiency.     

Selection of aptamers for a non-DNA binding protein in the context of cell lysate

Aptamer-facilitated Protein Isolation from Cells (AptaPIC) is a recently introduced method that allows, in particular, generation of aptamers for a protein target in a context of a crude cell lysate. The approach enables efficient, tag-free, affinity purification of target proteins which are not available in a pure form a priori, and for which no affinity ligands are available. In the proof-of-principle work, AptaPIC was used to develop aptamers for and purify MutS, a DNA mismatch repair protein. The DNA-binding nature of MutS raised concerns that AptaPIC was not a generic technique and could be inapplicable to protein targets that do not possess native nucleic acid-binding properties. Here we prove that these concerns are invalid. We used AptaPIC to generate pools of aptamers for human Platelet-Derived Growth Factor chain B (PDGF-B) protein, a non-DNA binding protein, in the context of a bacterial cell lysate, and subsequently purify it from the same lysate. Within a small number of rounds, the efficiencies of aptamer selection were similar in conventional Systematic Evolution of Ligands by Exponential Enrichment (SELEX) for pure protein and in AptaPIC for protein in the cell lysate. The conventional selection approach resulted in an aptamer pool with an EC(50) value of 2.0±0.1 μM, while the AptaPIC selection approach resulted in a pool with an EC(50) value of 3.9±0.4 μM. Our results clearly demonstrate that selection of aptamers for proteins in the cell lysate is not only realistic but also efficient.     

Development and molecular recognition of Calixcrownchip as an electrochemical ALT immunosensor

The developments of immunosensors with a variety of formats are increasingly finding applications in clinical diagnostics and biological researches. A strategy for the immunoassay and preparation of Calixcrownchips is proposed. This strategy is based on the immobilization of antigens or antibodies on the surface of Calixcrown and the direct electrochemistry of horseradish peroxidase (HRP) that was labeled to an antibody or antigen, with its activity determined by using tetramethylbenzidine (TMB) as an electrochemical substrate. The present study includes general considerations of the competitive immunoreaction protocols. Alanine aminotransferase (ALT) monoclonal antibody (anti-ALT-mAb) was successfully immobilized on thiol derivative of Calixcrown fixed to a gold surface. ALT antigen was detected by competitive immunoreactions based on microarrays of anti-ALT-mAb or antigen immobilized on the surface of the Calixcrownchip. For the anti-ALT-mAb immobilized microarray the dynamic range is 0.05 ng/mL–10 μg/mL, the detection limit is 0.05 ng/mL and the sensitivity is 10 nA/(ng/mL) respectively. The Calixcrownchip immunosensor microarray provided much better technical performance than a comparable enzyme sensor with immobilized-anti-ALT-mAb. To investigate the complexation site, the structures of the complexes formed between the crown-5-ether moiety of Calix[4]arene and protonated Arginine and Lysine were determined by minimizing the complex formation energies. The complex stability depends on the number of amine groups in the alkyl chain of the amino acid and also the number of methylene groups between the amine groups of the amino acid.