Aggregation and Gelation Behavior of Stereocomplexed Four-Arm PLA-PEG Copolymers Containing Neutral or Cationic Linkers.

Poly(lactide) (PLA) and poly(ethylene glycol) (PEG)-based hydrogels were prepared by mixing phosphate buffer saline (PBS, pH 7.4) solutions of four-arm (PEG-PLA)2-R-(PLA-PEG)2 enantiomerically pure copolymers having the opposite chirality of the poly(lactide) blocks. Dynamic Light Scattering, rheology measurements, and fluorescence spectroscopy suggested that, depending on the nature of the linker R, the gelation process followed rather different mechanisms. In all cases, mixing of equimolar amounts of the enantiomeric copolymers led to micellar aggregates with a stereocomplexed PLA core and a hydrophilic PEG corona. Yet, when R was an aliphatic heptamethylene unit, temperature-dependent reversible gelation was mainly induced by entanglements of PEG chains at concentrations higher than 5 wt.%. When R was a linker containing cationic amine groups, thermo-irreversible hydrogels were promptly generated at concentrations higher than 20 wt.%. In the latter case, stereocomplexation of the PLA blocks randomly distributed in micellar aggregates is proposed as the major determinant of the gelation process.

Rosmarinic and Glycyrrhetinic Acid-Modified Layered Double Hydroxides as Functional Additives for Poly(Lactic Acid)/Poly(Butylene Succinate) Blends.

Immobilizing natural antioxidant and biologically active molecules in layered double hydroxides (LDHs) is an excellent method to retain and release these substances in a controlled manner, as well as protect them from thermal and photochemical degradation. Herein, we describe the preparation of host-guest systems based on LDHs and rosmarinic and glycyrrhetinic acids, two molecules obtained from the extraction of herbs and licorice root, respectively, with antioxidant, antimicrobial, and anti-inflammatory properties. Intercalation between the lamellae of the mono-deprotonated anions of rosmarinic and glycyrrhetinic acid (RA and GA), alone or in the presence of an alkyl surfactant, allows for readily dispersible systems in biobased polymer matrices such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and a 60/40 wt./wt. PLA/PBS blend. The composites based on the PLA/PBS blend showed better interphase compatibility than the neat blend, correlated with increased adhesion at the interface and a decreased dispersed phase size. In addition, we proved that the active species migrate slowly from thin films of the composite materials in a hydroalcoholic solvent, confirming the optimization of the release process. Finally, both host-guest systems and polymeric composites showed antioxidant capacity and, in the case of the PLA composite containing LDH-RA, excellent inhibitory capacity against E. coli and S. aureus.

Compatibilization of Poly(Lactic Acid) (PLA)/Plasticized Cellulose Acetate Extruded Blends through the Addition of Reactively Extruded Comb Copolymers.

In the perspective of producing a rigid renewable and environmentally friendly rigid packaging material, two comb-like copolymers of cellulose acetate (AC) and oligo(lactic acid) OLA, feeding different percentages of oligo(lactic acid) segments, were prepared by chemical synthesis in solvent or reactive extrusion in the melt, using a diepoxide as the coupling agent and were used as compatibilizers for poly(lactic acid)/plasticized cellulose acetate PLA/pAC blends. The blends were extruded at 230 °C or 197 °C and a similar compatibilizing behavior was observed for the different compatibilizers. The compatibilizer C1 containing 80 wt% of AC and 14 wt% of OLA resulted effective in compatibilization and it was easily obtained by reactive extrusion. Considering these results, different PLAX/pAC(100-X) compounds containing C1 as the compatibilizer were prepared by extrusion at 197 °C and tested in terms of their tensile and impact properties. Reference materials were the uncompatibilized corresponding blend (PLAX/pAC(100-X)) and the blend of PLA, at the same wt%, with C1. Significant increase in Young's modulus and tensile strength were observed in the compatibilized blends, in dependence of their morphologic features, suggesting the achievement of an improved interfacial adhesion thanks to the occurred compatibilization.

State-of-the-Art Production Chains for Peas, Beans and Chickpeas-Valorization of Agro-Industrial Residues and Applications of Derived Extracts.

The world is confronted with the depletion of natural resources due to their unsustainable use and the increasing size of populations. In this context, the efficient use of by-products, residues and wastes generated from agro-industrial and food processing opens the perspective for a wide range of benefits. In particular, legume residues are produced yearly in very large amounts and may represent an interesting source of plant proteins that contribute to satisfying the steadily increasing global protein demand. Innovative biorefinery extraction cascades may also enable the recovery of further bioactive molecules and fibers from these insufficiently tapped biomass streams. This review article gives a summary of the potential for the valorization of legume residual streams resulting from agro-industrial processing and more particularly for pea, green bean and chickpea by-products/wastes. Valuable information on the annual production volumes, geographical origin and state-of-the-art technologies for the extraction of proteins, fibers and other bioactive molecules from this source of biomass, is exhaustively listed and discussed. Finally, promising applications, already using the recovered fractions from pea, bean and chickpea residues for the formulation of feed, food, cosmetic and packaging products, are listed and discussed.

Novel (glycerol)borate-based ionic liquids: an experimental and theoretical study.

A series of newly designed (glycerol)borate based ionic liquids were synthesized and characterized. The synthesis of these ionic liquids involves, first, the preparation of the bis(glycerol)boric acid(s) followed by neutralization with the appropriate base, [cat]OH. Ionic liquids bearing inorganic (Li(+), Na(+), K(+)) or organic cations have been prepared and characterized. The ability of the bis(glycerol)borate anions to undergo dissociation reaction in the presence of water, depending on cation nature, was investigated by NMR. Theoretical calculations were also performed to evaluate the relative stability of the possible bis(glycerol)borate isomers as nude ions or as ion pairs with Li(+), Na(+), and H(+). Important information about the structural features of H[Gly(2)B] useful to rationalize the chemical behavior have been obtained.

High-resolution poly(ethylene terephthalate) (PET) hot embossing at low temperature: thermal, mechanical, and optical analysis of nanopatterned films.

In this work we present controlled, low-damage nanotopographic surface modification of poly(ethylene terephthalate) (PET). High-resolution nanopatterning over macroscopic areas was performed by " low-temperature" hot embossing lithography (HEL). While for standard HEL the temperature is typically raised up to many tens of Celsius degrees above the polymer glass transition temperature (Tg), we demonstrate optimal results at a temperature very close to the bulk Tg of PET (72 degrees C). Nanopits and nanobarcodes were transferred onto the surface of PET commercial sheets, demonstrating reliable sub-100 nm resolution over macroscopic areas. Sample optical, mechanical, and thermal characteristics were systematically analyzed before and after embossing at low (75 degrees C) and high (150 degrees C) temperature by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, tensile tests, and differential scanning calorimetry (DSC). We show that, while conventional high-temperature HEL can lead to dramatic degradation of the polymer in terms of transparency, flexibility, and crystallinity content, our low-temperature process fully maintains original surface and bulk substrate properties.

New perspectives for (S)-dolichol and (S)- nor dolichol synthesis and biological functions.

A procedure is described for the preparation of (S)-dolichol and (S)- nor dolichol starting from the polyprenyl fraction extracted from Gingko biloba integer or exhausted leaves. The procedure appears extremely valuable in obtaining the two chiral isoprenoid compounds in good chemical yields and retention of a high degree of enantiomeric excess. Also, the (S)- nor dolichol represents a good chiral precursor for the preparation of (14)C-labelled (S)-dolichol to be used in biological investigations into the (S)-dolichol catabolism in the functional living cell. Furthermore, the possible role of (S)-dolichol as a free radical scavenger in the cell membrane was preliminarily evaluated by means of a (1)H-NMR analytical method. Apparently, experimental results substantiate this hypothesis.

Dolichol: a solar filter with UV-absorbing properties which can be photoenhanced.

Dolichol, the polyisoprenoid lipid found in all eukaryotic cells and suggested to represent a biomarker of aging, is inserted into cell membranes, also in tissues exposed to light such as the skin. A general question about its physiological role is whether dolichol may play the role of a natural barrier for the noxious components of solar radiation. In order to clarify this point, we established that dolichol is a component of human sebum and we performed an " in vitro " study of the effects of UV radiation on the spectral properties of dolichol in isopropanol. Our data clearly show that, following UV irradiation, the optical absorption spectrum of dolichol undergoes remarkable modifications below 400 nm: a significant, strongly dose-dependent, increase of the optical density around 320 nm and a minor, very slightly dose-dependent, raise of the absorbance at 250 nm. On the contrary, UV irradiation causes only minor changes in HPLC profiles and the formation of photooxidative products can be considered negligible in our experimental conditions. These results suggest that dolichol can be considered an innate, unusually efficient and promising UV screen for skin protection.