Valorization of not soluble byproducts deriving from green keratin extraction from poultry feathers as filler for biocomposites

The valorization of poultry feathers wastes is very important to reduce the environmental pollution deriving from their disposal. In this frame, we present the production process of completely natural, biodegradable, biocompatible, and eco-friendly composites made by not soluble keratin (NSK) and poly(lactic acid) (PLA). NSK has been obtained as a byproduct of a microwave-assisted keratin extraction from poultry feathers and it has been added to PLA pellets without adding any additional compatibilizers or plasticizers, unlike from the other works reported in the literature until now. The mixture has been used to obtain homogeneous NSK-based PLA filaments by means of hot-melt extrusion technology. The filaments have been subsequently 3D printed to explore applications in the additive manufacturing field. All the samples have unaltered thermal stability, but reduced toughness with respect to neat PLA. Other tested parameters (water adsorption, glass transition, and crystallinity) are dependent on NSK content and fabrication technology. Besides, Fourier Transform Infrared Spectroscopy highlights the differences in the structure of the NSK-based PLA filaments and 3D printed samples

One-pot process: Microwave-assisted keratin extraction and direct electrospinning to obtain keratin-based bioplastic

Poultry feathers are among the most abundant and polluting keratin-rich waste bio-masses. In this work, we developed a one-pot microwave-assisted process for eco-friendly keratin extraction from poultry feathers followed by a direct electrospinning (ES) of the raw extract, without further purification, to obtain keratin-based bioplastics. This microwave-assisted keratin extraction (MAE) was conducted in acetic acid 70% v/v. The effects of extraction time, solvent/feathers ratio, and heating mode (MAE vs conventional heating) on the extraction yield were investigated. The highest keratin yield (26 ± 1% w/w with respect to initial feathers) was obtained after 5 h of MAE. Waste-derived keratin were blended with gelatin to fabricate keratin-based biodegradable and bio-compatible bioplastics via ES, using 3-(Glycidyloxypropyl)trimethoxysilane (GPTMS) as a cross-linking agent. A full characterization of their thermal, mechanical, and barrier properties was performed by differential scanning calorimetry, thermogravimetric analysis, uniaxial tensile tests, and water permeability measurements. Their morphology and protein structure were investigated using scanning electron microscopy and attenuated total reflection-infrared spectroscopy. All these characterizations highlighted that the properties of the keratin-based bioplastics can be modulated by changing keratin and GPTMS concentrations. These bioplastics could be applied in areas such as bio-packaging and filtration/purification membranes

Structure effects on the reactivity of two new cyanine/DNA systems

Cyanines are a class of fluorescent molecules that play an important role in the biochemical field. Due to the high affinity towards double strands of nucleic acids, they are used to selectively stain these bio-substrates and can play a role in DNA fragments sequencing, and in conformational studies of biomolecules based on FRET. New cyanines are tested with the aim to optimise their properties, both in terms of selectivity and in photo-physical behaviour. Two different cyanine/DNA systems have been analysed by spectrophotometric and spectrofluorometric titrations under different (salt content and temperature) conditions. The molecular structure of the two cyanines used, Cy-Ph and Cy-dPh, differ for the presence, in Cy-dPh, of an additional phenyl ring that enhances the possible aromatic extension of the system. The results obtained show that both dyes bind DNA with high affinity, intercalating between the polynucleotide base-pairs. For both systems the binding features strongly depend on the salt content of the medium, enlightening the importance of dye/DNA electrostatic attraction in the binding process. The higher aromatic extension of Cy-dPh plays an important role. The binding constant are significantly higher for the Cy-dPh/DNA system with respect to the Cy-Ph/DNA system. The thermodynamic parameters of binding (DH and DS) are also higher for the Cy-dPh/DNA system. Interestingly, when these values are reported in a Chaires plot [2], the values for the latter system approach to the higher-energy cluster of bis-intercalators. The possible ability of Cy-dPh to bis-intercalate into DNA would agree with some deviations occurring in the binding isotherms under high DNA loading conditions. This aspects will be further analysed by means of mechanistic studies based on fast reaction techniques

Non-covalent interactions in thermodynamic stereoselectivity of mixed-ligand copper(II)-D- or L-histidine complexes with L-amino acids. A possible model of metal ion-assisted molecular recognition

Formation constants of ternary complexes of copper(II), L/D-histidine and, in turn, glycine, L-alanine, L-valine, L-leucine, L-tryptophan, or L-phenylalanine have been determined potentio-metrically at 25 °C and I= 0.1 mol dm–3(KNO3). In the case of amino acids with aromatic side chains the ternary complexes containing ligands of opposite chirality are more stable than those having ligands of the same chirality; the opposite is true for amino acids with aliphatic residues. Calorimetric measurements have been carried out to obtain the enthalpy and entropy values associated with complex formation. Copper(II)–histamine ternary systems with L-alanine or L-phenylalanine have also been investigated. Comparison of the thermodynamic parameters pertinent to formation of the histamine complexes with those of the analogous histidine complexes allows one to ascertain the number of donor atoms involved in the co-ordination to copper(II), in the histidine systems. The determination of H and S values renders easier understanding of the factors determining Stereoselectivity in the above systems. The Stereoselectivity may be explained in terms of non-covalent interactions between side-chain residues. The role played by the histidine carboxylate in the molecular recognition of amino acids is also discussed

New polymeric sorbent for the solid-phase extraction of indole-3-acetic acid from plants followed by liquid chromatography - Fluorescence detector

Plant hormones play a crucial role in controlling plant growth and development. These groups of naturally occurring substances trigger physiological processes at very low concentrations, which require sensitive techniques for their quantitation.This study reports on the development of a newly synthesized polymer sorbent for the analysis of indole-3-acetic acid (IAA), which is the most important auxin in plants, from complex raw matrices, such as plant extracts. IAA was determined by high-performance liquid chromatography (HPLC) coupled with fluorescence detection (FD).The polymer developed was able to bind about 94% of IAA with a reproducible manner. The release of IAA in methanol was more than 70% for both of them. Non-specific hydrophobic interactions are, likely, the dominant driving force of the binding between IAA and the polymer.This methodology was applied for the determination of IAA in raw lemon leaves. The detection and quantification limits for IAA in real samples were 0.50 ± 0.08 ng/g and 2.64 ± 0.09 ng/g (n = 3, α = 0.05), respectively. As expected, the IAA concentration in uninfected lemon sample was significantly lower respect to the concentration found in infected sample

Pectin as rheology modifier of a gelatin-based biomaterial ink

Gelatin is a natural biopolymer extensively used for tissue engineering applications due to its similarities to the native extracellular matrix. However, the rheological properties of gelatin formulations are not ideal for extrusion-based bioprinting. In this work, we present an approach to improve gelatin bioprinting performances by using pectin as a rheology modifier of gelatin and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) as a gelatin–pectin crosslinking agent. The preparation of gelatin–pectin formulations is initially optimized to obtain homogenous gelatin–pectin gels. Since the use of GPTMS requires a drying step to induce the completion of the crosslinking reaction, microporous gelatin–pectin–GPTMS sponges are produced through freeze-drying, and the intrinsic properties of gelatin–pectin–GPTMS networks (e.g., porosity, pore size, degree of swelling, compressive modulus, and cell adhesion) are investigated. Subsequently, rheological investigations together with bioprinting assessments demonstrate the key role of pectin in increasing the viscosity and the yield stress of low viscous gelatin solutions. Water stable, three-dimensional, and self-supporting gelatin–pectin–GPTMS scaffolds with interconnected micro-and macroporosity are successfully obtained by combining extrusion-based bioprinting and freeze-drying. The proposed biofabrication approach does not require any additional temperature controller to further modulate the rheological properties of gelatin solutions and it could furthermore be extended to improve the bioprintability of other biopolymers

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