Valorization of agar production residue as a filler in soy protein hydrogels for 3D printing.

Cellulose-containing residue from agar production was incorporated as a filler into soy protein-based hydrogels and revalorized without further purification. Rheological assessment of these hydrogels was carried out in order to confirm their shear-thinning behavior and their suitability for 3D printing. It was observed that all hydrogels behaved as weak gels, which are suitable for 3D printing and have good printability and shape fidelity. The addition of cellulose did not cause chemical crosslinking but physical interactions, which led to morphological changes, thereby promoting hardness and shape recovery of the 3D-printed products. The hydrogel with the highest residue content (8 wt %) showed the highest value (78%) in shape recovery. Furthermore, the physicochemical characterization of these 3D-printed products revealed that although they have high swelling capacity, they preserve their integrity in wet conditions. These results suggested the potential of the 3D-printed products developed using residues without further purification to promote circular economy, increasing the efficiency in resources utilization.

Effect of Fructose and Ascorbic Acid on the Performance of Cross-Linked Fish Gelatin Films.

Gelatin was extracted from fish scales in this work, in an attempt to valorise abundant and available fishery by-products as an approach towards a more circular economy. With this strategy in mind, fish scale gelatin was used to prepare active films. In this regard, the development of advanced materials from gelatin involves its modification to enhance functional properties, particularly barrier properties, to achieve the requirements for specific value-added purposes, such as food or pharmaceutical/biomedical applications. The improvement of those functional properties can be achieved by means of chemical cross-linking processes. In this context, non-enzymatic reactions were carried out with the addition of fructose and ascorbic acid into gelatin film forming formulations, and cross-linking was induced by a heat-treatment. These cross-linking reactions resulted in higher barrier features, especially for those films prepared with ascorbic acid.

ZnO nanoparticle-incorporated native collagen films with electro-conductive properties.

Collagen obtained from bovine skin was mechanically pre-treated with the aim of preserving the triple helix structure of native collagen. Furthermore, zinc oxide nanoparticles were incorporated into film forming formulations due to their inherent biological properties, which are of great relevance for biomedical applications. All the films showed good mechanical properties with a predominant elastic behavior, as shown by dynamic mechanical analysis (DMA) curves, and collagen films were easy to handle in both dry and wet states. It is worth noting that the integrity in the wet state was achieved without incorporating chemical crosslinkers, in contrast to chemically treated collagen that must be crosslinked chemically due to collagen denaturation after the pre-treatment. As shown by Fourier Transform Infrared (FTIR) spectroscopy analysis, collagen preserved the triple helix structure, although a slight decrease was observed with the increase of zinc oxide nanoparticles (ZnO NPs) content, which slightly increased the equilibrium swelling values and also caused some changes in the denaturation collagen peak observed above 200 °C by Differential Scanning Calorimetry (DSC) measurements. Additionally, collagen films showed good barrier properties, protection again Ultraviolet (UV) light and optimal Water Vapor Permeability (WVP) values (occlusivity) for biomedical purposes such as wound healing, since the WVP values measured would allow exudates' absorption. Regarding electrical conductivity, collagen films presented a semiconductor behavior and memory properties and, thus, these films could be used as biosensors.