Marina Zoccola

Study on Cast Membranes and Electrospun Nanofibers Made from Keratin/Fibroin Blends

Keratin regenerated from wool and fibroin regenerated from silk were mixed in different proportions using formic acid as the common solvent. Both solutions were cast to obtain films and electrospun to produce nanofibers. Scanning electron microscopy investigation showed that, for all electrospun blends (except for 100% keratin where bead defects are present), the fiber diameter of the mats ranged from 900 (pure fibroin) to 160 nm (pure keratin). FTIR and DSC analysis showed that the secondary structure of the proteins was influenced by the blend ratios and the process used (casting or electrospinning). Prevalence of beta-sheet supramolecular structures was observed in the films, while proteins assembled in alpha-helix/random coil structures were observed in nanofibers. Higher solution viscosity, thinner filaments, and differences in the thermal and structural properties were observed for the 50/50 blend because of the enhanced interactions between the proteins.

Morphological and structural investigation of wool-derived keratin nanofibres crosslinked by thermal treatment

Mats of wool-derived keratin nanofibre have been prepared by electrospinning solutions of keratin in formic acid at 20 and 15 wt.%, and obtaining nanofibres with mean diameter of about 400 and 250 nm, respectively. These mats can find applications in tissue engineering (they can mimic the native extracellular matrix) and in wastewater treatment (they can trap small particles and adsorb heavy-metals). A drawback to overcome is their solubility in water. A stabilization method, based on a thermal treatment alternative to the use of formaldehyde, is proposed. The solubility test in the dithiothreitol/urea extraction buffer, the amino acid composition analysis and studies on keratin secondary structures suggest that the improved stability in water of thermally treated mats can be ascribed to the formation of amide bonds between acid and basic groups of some amino acid side chains.

Microwave-assisted chemical-free hydrolysis of wool keratin

Wool fibers were submitted to “green hydrolysis” with superheated water in a microwave reactor, in view of the potential exploitation of keratin-based industrial and stock-farming wastes. The liquid fraction was separated by filtration from the solid fraction, which consists mainly of small fragments of wool fibers and other insoluble protein aggregates. The liquid fraction contains free amino acids, peptides and low molecular weight proteins, with a small amount of cystine and lanthionine, and has a different secondary structure when compared with keratins extracted from wool via reductive or oxidative methods. Cleavage of the cystine disulfide bonds without the use of harmful, often toxic, reductive or oxidative agents allows the extraction of protein material from keratin wastes, offering the possibility of larger exploitation and valorization.

Electrospinning of polyamide 6/modified-keratin blends

Abstract Protein material resulting from chemical free steam explosion of wool was mixed in different proportion with polyamide 6 in formic acid. The viscosity of the blend solutions decreases with the increase of the protein amount in the blend. Nanofibres produced by electrospinning of these polymer blends show an increase of the filament diameters with increasing protein amounts, except for the 30/70 v/v polyamide 6/protein blend, where nanofibres with “beads” defects were produced. In blend films produced by casting, polyamide 6 crystallize in the form of large spherulites prevalently in the α crystalline structure, while protein is totally amorphous and tends to segregate in the course of drying at room temperature. Otherwise, in electrospun nanofibres polyamide 6 and protein show a better miscibility as suggested by spectroscopic and thermal analysis and polyamide 6 shows a higher thermal stability. Moisture regain and water solubility of blend cast films and electrospun nanofibres respectively were also determined.

Comparative study on the effects of superheated water and high temperature alkaline hydrolysis on wool keratin

The purpose of this work is to understand the impact of superheated water hydrolysis treatment on the chemical properties of wool, and compare it with a conventional method of alkaline hydrolysis. The effects of hydrolysis temperature and concentration of alkali on the properties of wool were investigated. Superheated water hydrolysis was carried out at the temperatures of 140℃ and 170℃, with a material to liquor ratio of 1:3 for 1 hour. In conventional alkaline hydrolysis, the experiments were carried out in the same conditions using potassium hydroxide (KOH) and calcium oxide (CaO) with a concentration in the range of 5%–15% on the fiber weight (o.w.f.). The effects of hydrolysis temperature and alkali concentrations on wool properties were checked using optical and scanning electron microscopy. It was observed that the hydrolyzates obtained in both cases contained low molecular weight proteins and amino acids. Both the hydrolysis processes resulted in degradation of the wool fibers. However, superheated steam hydrolysis is an environmentally friendly and less expensive process, as it is performed using water as a solvent. The wool hydrolyzates produced using superheated water hydrolysis could find a potential application in agriculture, such as fertilization, soil improvement and suchlike.

Wool cortical cell-based porous films

The aim of this work is to improve the select mechanical properties of keratin films for biomedical application by exploiting the hierarchical cell structure of wool fibers in a simple and green process. Bio-composite keratin films were prepared by ultrasonic irradiation of wool fibers soaked in clean water, have previously been swollen in mild alkali. The disruption of the fiber cell structure produced a suspension of cortical cells that was centrifuged and rinsed to remove part of the hydrolyzed keratin matrix, then cast into micro-structured porous films made of randomly oriented cortical cells stuck to each other by solidification of the matrix. The chemical and physical properties of the porous films were compared with those of compact films produced using the entire hydrolyzed keratin matrix. Reduction of the keratin matrix amount leads to an even micro-porous structure and improves the mechanical properties (ultimate tensile strength: 11.36 MPa; elongation at break: 3.18%), the moisture uptake and the thermal stability of the films. These properties, associated with other properties of wool keratin, which is naturally hydrophilic, non-burning, biodegradable and biocompatible, make the porous bio-composite keratin films simple and low-cost candidates for biomedical and biotechnology applications.

Electrically conducting linen fabrics for technical applications

Conducting linen fabrics were prepared by the in situ oxidative polymerization of pyrrole using ferric chloride as the oxidant and anthraquinone-2,6-disulfonic acid disodium salt as the dopant to enhance conductivity. The effect of the pyrrole concentration on the final performance and properties of the conducting fabrics was evaluated. Scanning electron microscopy and light microscopy showed a polypyrrole layer deposited on the fiber surface associated with penetration into the bulk fiber at the highest concentrations of pyrrole. Saturation of the amorphous domains of the cellulose structure and coating of the fiber surface resulted in good electrical properties, heat development by the Joule effect and reduced moisture adsorption. The mechanical properties and electrical conductivity of the fabrics were affected by the strong acid conditions of the treatment, but significant electrical properties were achieved while preserving up to 70% of the original tensile strength.

Preparation of keratin-based microcapsules for encapsulation of hydrophilic molecules

The interest towards microcapsules based on non-toxic, biodegradable and biocompatible polymers, such as proteins, is increasing considerably. In this work, microcapsules were prepared using water soluble keratin, known as keratoses, with the aim of encapsulating hydrophilic molecules. Keratoses were obtained via oxidizing extraction of pristine wool, previously degreased by Soxhlet. In order to better understand the shell part of microcapsules, pristine wool and obtained keratoses were investigated by FT-IR, gel-electrophoresis and HPLC. Production of the microcapsules was carried out by a sonication method. Thermal properties of microcapsules were investigated by DSC. Microencapsulation and dye encapsulation yields were obtained by UV-spectroscopy. Morphological structure of microcapsules was studied by light microscopy, SEM, and AFM. The molecular weights of proteins analyzed using gel-electrophoresis resulted in the range of 38-62kDa. The results confirmed that the hydrophilic dye (Telon Blue) was introduced inside the keratoses shells by sonication and the final microcapsules diameter ranged from 0.5 to 4µm. Light microscope investigation evidenced the presence of the dye inside the keratoses vesicles, confirming their capability of encapsulating hydrophilic molecules. The microcapsule yield and dye encapsulation yield were found to be 28.87±3% and 83.62±5% respectively.

Physicochemical properties of keratin extracted from wool by various methods

Keratin from wool fibers was extracted with different extraction methods, for example oxidation, reduction, sulfitolysis, and superheated water hydrolysis. Different samples of extracted keratin were characterized by molecular weight determination, FT-IR and NIR spectroscopy, amino acid analysis, and thermal behavior. While using oxidation, reduction, and sulfitolysis, only the cleavage of disulfide bonds takes place; keratin hydrolysis leads to the breaking of peptide bonds with the formation of low molecular weight proteins and peptides. In the FT-IR spectra of keratoses, the formation of cysteic acid appears, as well as the formation of Bunte salts (–S–SO3–) after the cleavage of disulfide bonds by sulfitolysis. The amino acid composition confirms the transformation of amino acid cystine, which is totally converted into cysteic acid following oxidative extraction and almost completely destroyed during superheated water hydrolysis. Thermal behavior shows that keratoses, which are characterized by stronger ionic interaction and higher molecular weight, are the most temperature stable keratin, while hydrolyzed wool shows a poor thermal stability.

Mitigation of the Impact Caused by Microfibers Released During Washings by Implementing New Chitosan Finishing Treatments

Until today, many studies (Hidalgo-Ruz and Gutow et al. in Environ SciTechnol 46:3060–3075, 2012; Auta et al. in Environ Int 102:165–176, 2017) were focused on the origin or the formation mechanisms of microplastics. Microplastics comprise a very heterogeneous group of fragments that vary in size, shape, color, specific density, chemical composition, and other characteristics.