Transparent Bioplastic Derived from CO2-Based Polymer Functionalized with Oregano Waste Extract toward Active Food Packaging.

Active packaging materials, biodegradable and from renewable resources, are the most promising substitutes of nonbiodegradable, petroleum-based plastics, toward green and sustainable packaging solutions. In this study, an innovative bioplastic system, composed of carbon dioxide-derived poly(propylene carbonate) (PPC) and nature-originated cellulose acetate (CA), was developed. The extract from oregano waste was incorporated into the bioplastics as a low-cost and effective antioxidant resource. Thin, freestanding, and flexible PPC.CA bioplastic films were obtained by a simple, easily scalable solvent casting technique. The pristine films, without the oregano extract, featured good transparency and high water vapor barrier ability, along with suitable mechanical and thermal properties that are comparable to commercial plastics used for packaging. Interestingly, the incorporation of oregano waste extract added to the bioplastics high UV protection and high antioxidant activity, suitable features for active food packaging applications, without compromising the intriguing properties of the pristine films. The biocomposite films were not only biocompatible but also started biodegrading after just 1 week in seawater. The reported biocomposites are foreseen as promising candidates for several packaging applications, but in particular for sustainable active food packaging.

Hydrogen-Bonding UCST-Thermosensitive Nanogels by Direct Photo-RAFT Polymerization-Induced Self-Assembly in Aqueous Dispersion.

Hydrogen-bonding upper critical solution temperature (UCST) thermosensitive nanogels based on poly(N-acryloyl glycinamide) (PNAGA) are synthesized by photo-reversible addition-fragmentation chain transfer mediated polymerization-induced self-assembly (photo-RAFT PISA) in aqueous dispersion using N,N'-methylenebis(acrylamide) as crosslinker and poly(oligo(ethylene glycol) methyl ether acrylate) as both stabilizer and macromolecular chain transfer agent (macro-CTA). Highly stable, spherical nanogels with narrow polydispersity are efficiently produced up to complete monomer conversion within 1 h under UV irradiation at low temperature (3 °C). The thermosensitive behavior of PNAGA-based nanogels, as assessed by dynamic light scattering and UV-vis spectrophotometry, exhibits reversible heating-induced swelling and cooling-induced shrinking corresponding to the expected UCST behavior. The hydrodynamic diameter, swelling ratio, and phase transition temperature of nanogels can be tuned by modifying the initial molar ratio of monomer-to-macro-CTA and the amount of crosslinker in the photo-RAFT PISA of NAGA.

Sustainable Active Food Packaging from Poly(lactic acid) and Cocoa Bean Shells.

Sustainable biocomposites have been developed by solvent mixing of poly(lactic acid) (PLA) with a fine powder of cocoa bean shells (CBS) and subsequent solution casting, using different concentrations of CBS. The inclusion of CBS recovers the crystallinity of the initially amorphous PLA films and improves the physical properties of the composites. Young's modulus increases by 80% with 75 wt % CBS inclusion; however, the composites maintain plasticity. The barrier properties of the hydrophobic composites were characterized, and the water vapor permeability is found to be ca. 3.5 × 10-5 g·m-1·day-1·Pa-1 and independent of the CBS content. On the other hand, oxygen permeability is found to depend on the CBS content, with values as low as 10 000 mL·µm·m-2·day-1·atm-1 for 50 wt % CBS. Furthermore, CBS confer antioxidant activity to the composites and improve swelling properties rendering the composites biodegradable in aquatic environments, reaching 70% of the maximum biodegradability in just 30 days. The above, in conjunction with the low level of migration measured in food simulant, make the PLA/CBS composites a highly promising material for active food packaging.

Formation of Cross-Linked Films from Immiscible Precursors through Sintering of Vitrimer Nanoparticles.

Colloidal dispersions of epoxy-acid vitrimers have been synthesized by miniemulsion polymerization. This versatile strategy enables obtaining stable cross-linked particles, even from initially incompatible precursors, while minimizing hydrolysis of the ester bonds formed during the curing. After drying of the latexes, trans-esterification exchanges occurring at high temperatures through interparticle interfaces induces an efficient sintering into homogeneous cross-linked polymer films.

Expression of a novel complement C3 gene in the razor clam Sinonovacula constricta and its role in innate immune response and hemolysis.

Complement component 3 (C3) is a core component of the complement system, and directly participates in immune regulation and immune defense. Isoforms of C3 have been reported in several species of vertebrate, but invertebrates, and more specifically clams, have been less well studied. An isoform of C3, named ScC3-2, was identified in Sinonovacula constricta (Chinese razor clam). ScC3-2 included eight conserved regions, a thioester bond and two predicted junction sites (α-ß and α-γ). The gene was expressed in the liver, gill, foot, hemolymph, mantle, gonad and siphon tissues. The gene was significantly upregulated in umbo larvae, suggesting that initial larval immunity may develop in umbo larvae. Moreover, the ScC3-2 mRNA expression patterns after challenge with Vibrio parahemolyticus and Micrococcus lysodeikticus exhibited an obvious upregulation at 8 h in the hemolymph and at 4 h in the liver, respectively. Furthermore, ScC3-2 showed effective membrane rupture of heterologous rabbit erythrocytes. The ScC3-2 protein was located on the surface of the cells during the process of hemolysis. After a comparative analysis, we suggest that the major structure and function of ScC3 and ScC3-2 are analogous. Our findings suggest that ScC3-2 plays an important immune function, and an intricate complement response may exist in S. constricta.

Starch-based bio-elastomers functionalized with red beetroot natural antioxidant.

Red beetroot (RB) powder was incorporated into starch-based bio-elastomers to obtain flexible biocomposites with tunable antioxidant properties. Starch granules within the bio-elastomers affected the release of the antioxidant molecule betanin in the RB powder. The bio-elastomers were hydrophobic and resisted dissolution in water, hence the release of betanin was due to diffusion rather than polymer matrix disintegration. Hydrophobicity was maintained even after water immersion. Released betanin demonstrated highly efficient antioxidant scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(+)). RB powder was also found to increase the Young's modulus of the bio-elastomers without compromising their elongation ability. Infrared spectral analysis indicated weak interactions through hydrogen bonding among starch granules, RB powder and PDMS polymer within the bio-elastomers. Hence, as a simple but intelligent biomaterial consisting of mainly edible starch and RB powder the present bio-elastomers can be used in active packaging for a variety of pharmaceutical, medical, and food applications.

Covalent Incorporation of SiO2 Nanoparticles in CO2-Based Copolymers: Synthesis, Characterization, Morphology and Property Studies.

A new strategy has been developed for covalent incorporation of SiO2 nanoparticles (N-'s) in the CO2-based copolymer, poly(propylene carbonate-co-propylene oxide) (poly(PC-co-PO)). The poly(PC-co-PO)-g-SiO2 nanocomposites was prepared by the combination of epoxy-CO2 ring-opening polymerization and the condensation reaction of chloride and hydroxyl groups of the polymer and the SiO2 surface. FT-IR and NMR were employed for the characterization of the copolymers as well as nanocomposites. A uniform and spherical core-shell structure of poly(PC-co-PO)-g-SiO2 nanocomposites was demonstrated from TEM and SEM images. An improved thermal property of the polymer matrix with incorporating SiO2 nanoparticles was revealed by TGA study. The grafting of poly(PC-co-PO) considerably prevented the aggregation and improved the dispersibility of SiO2 nanoparticles in toluene.

Facile synthesis of ZnO-poly(2-hydroxyethyl methacrylate) nanocomposites by surface-initiated ARGET atom transfer radical polymerization.

The covalent attachment of poly(2-hydroxyethyl methacrylate) on ZnO nanoparticles (NPs) has been achieved by ARGET ATRP. The polymer chains were grown from the surface of ATRP-initiator modified ZnO NPs with a copper (II) catalyst under activation of zerovalent copper as a reducing agent. FT-IR, FE-SEM, TEM and TGA were employed for the characterization of the nanocomposites. GPC was used to determine the molecular weight and PDI of the cleaved polymer. The covalent attachment of polymer chains onto the surface of ZnO NPs was sufficiently confirmed by FT-IR. In addition, the formation of the polymer encapsulating ZnO cores was demonstrated from TEM and SEM images. It was found that the growing of polymer brushes from the ZnO surface could be induced even though the catalyst amount was reduced to 10 ppm without loss of inherent control manner. This report contributed to demonstrate the versatility and feasibility of ATRP-based surface-initiated polymerization for the preparation of inorganic/polymer nanocomposites.