Silk degumming is considered the first point in the preparation of silk-based materials since this process could modify the silk fiber and the properties of its related products. This study evaluated the differences in morphology, secondary structure, amino acid content, thermal stability, and mechanical properties of two types of raw materials, defective cocoons (DC) and silk fibrous waste (SW), degummed by chemical (C) and autoclaving (A) methods. Subsequently, silk fibroin films were prepared by dissolving each type of degummed fibers, and thermal and structural films properties were determined. The findings demonstrated that autoclaving is an efficient alternative to remove silk sericin, as the resulting fibers presented improved structural, thermal, and mechanical properties compared to those obtained by the chemical method. For films preparation, autoclave resulted in a good option, but dissolution parameters need to be adjusted for defective cocoons. Furthermore, similarities between the physicochemical properties of fibers and films from both fibrous wastes suggest that SW is a promising raw material for producing fibrous resources and regenerated silk fibroin materials. Overall, these findings suggest new recycling methods for fibrous waste and by-products generated in the silk textile production process.

Sericin has been used in functional and potentially biodegradable materials for cosmetics, biomedical, agricultural, and food applications. It is a natural polymer with applications in absorbent materials, such as hydrogels, because of its hydrophilic character. However, sericin by itself is brittle, and in contact with water has low structural stability, being necessary its blending with other polymers or the application of crosslinking processes. In this work, hydrogel films were prepared from different mixtures containing sericin (SS), carboxymethylcellulose (CMC), and polyvinyl alcohol (PVA), using a simple and environmentally friendly method consisting of a gelling process followed by solvent casting. A mixture design was applied to assess the incidence of each component and its interaction with the output variables of interest. Two response variables were evaluated in each formulation: water absorption capacity (WA) and gel fraction (GF). It was also possible to model the output variables based on the proportions of the sample components. In addition, a set of formulations were used to produce hydrogels with high water absorption rates while maintaining their structural stability. The optimal hydrogel formulation (HF) was structurally and thermally characterized by FTIR and TGA, respectively. Hydrogel morphology was also studied by scanning electron microscopy (SEM). The results of this study constitute an important contribution to the design of novel processing routes to extend the use of silk sericin in the development of new materials.

The use of silk proteins sericin (SS) and fibroin (SF) has been increased for biomedical applications. In order to improve their behavior inside of biological environment, silk biomaterials must be treated after their manufacturing by means of diverse methods. These include ethanol post-treatments to increase their crystallinity, mechanical properties and water stability. In this study, the effect of ethanol post-treatments on the properties of silk protein materials was evaluated. Defective cocoons and silk fibrous waste (SW) were used to obtain silk sericin sponges (S-SS) and silk fibroin films (F-SF), respectively. Two ethanol treatments were evaluated in SS and SF: immersion (I) and solvent vapor annealing (SVA). Morphological modifications induced by ethanol post-treatments were studied by scanning electron microscopy (SEM). Conformational structure of the samples was analyzed by attenuated total reflectance–Fourier-transform infrared spectroscopy (ATR–FTIR), and the thermal properties were evaluated by differential scanning calorimetry (DSC) measurements. SEM images revealed that ethanol process induces changes in treated F-SF and S-SS, the material surfaces are more roughness, and these effects were more pronounced in samples treated by I than that subjected to SVA. As a result of the ethanol treatments, the ATR–FTIR and DSC results showed an increment in relative content of β-sheet structures in both silk protein materials. The results suggest that ethanol post-treatments induce conformational transitions and morphological modifications in S-SS and F-SF that should be considered to select the post-treatment conditions according to the biomedical application requirements.