Agar/gelatin hydro-film containing EGF and Aloe vera for effective wound healing.

In the current study, we produced a hydro-film dressing for the treatment of chronic wounds. The hydro-film structure was composed of gelatin cross-linked with citric acid, agar and Aloe vera extract (AV); additionally epidermal growth factor (EGF) was loaded to promote wound healing. Due to the excellent hydrogel-forming ability of gelatin, the obtained hydro-film was able to swell 884 ± 36% of its dry weight, which could help controlling wound moisture. To improve gelatin mechanical properties, polymer chains were cross-linked with citric acid and agar, reaching an ultimate tensile strength that was in the highest range of human skin. In addition, it showed a slow degradation profile that resulted in a remaining weight of 28 ± 8% at day 28. Regarding, biological activity, the addition of AV and citric acid provided the ability to reduce human macrophage activation, which could help reverse the permanent inflammatory state of chronic wounds. Moreover, loaded EGF, together with the structural AV of the hydro-film, promoted human keratinocyte and fibroblast migration, respectively. Furthermore, the hydro-films presented excellent fibroblast adhesiveness, so they could be useful as provisional matrices for cell migration. Accordingly, these hydro-films showed suitable physicochemical characteristics and biological activity for chronic wound healing applications.

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.

Combination of 3D printing and electrospinning to develop chitin/gelatin/PVA scaffolds.

In this study, novel scaffolds based on natural polymers were developed by combining 3D printing (3DP) and electrospinning (ES) techniques. ES ink was prepared with gelatin and poly(vinyl alcohol) (PVA), while 3DP ink was prepared with gelatin and chitin. Different biopolymers were used to confer unique properties to each ink and obtain a multilayered scaffold suitable for tissue regeneration. First, gelatin is able to exhibit the characteristics needed for both inks since gelatin chains contain arginineglycine-aspartic (RGD) motifs, an important sequence in the promotion of cell adhesion, which gives gelatin an improved biological behavior in comparison to other polymers. Additionally, PVA was selected for ES ink to facilitate gelatin spinnability, and chitin was incorporated into 3DP ink as reinforcement to provide mechanical support and protection to the overall design. In this work, chitin was extracted from fruit fly pupae. The high extraction yield and purity of the chitin obtained from the fruit fly pupae confirmed that this pupa is an alternative source to produce chitin. Once the chitin was characterized, both inks were prepared and rheological analysis was carried out in order to confirm the shear thinning behavior required for additive manufacturing processes. The combination of 3DP and ES processes resulted in porous scaffolds, which were proven biocompatible, highlighting their potential for biomedical applications.

Green hemostatic sponge-like scaffold composed of soy protein and chitin for the treatment of epistaxis.

Epistaxis is one of the most common otorhinolaryngology emergencies worldwide. Although there are currently several treatments available, they present several disadvantages. This, in addition to the increasing social need of being environmentally respectful, led us to investigate whether a sponge-like scaffold (SP-CH) produced from natural by-products of the food industry - soy protein and ß-chitin - can be employed as a nasal pack for the treatment of epistaxis. To evaluate the potential of our material as a nasal pack, it was compared with two of the most commonly used nasal packs in the clinic: a basic gauze and the gold standard Merocel®. Our SP-CH presented great physicochemical and mechanical properties, lost weight in aqueous medium, and could even partially degrade when incubated in blood. It was shown to be both biocompatible and hemocompatible in vitro, clearing up any doubt about its safety. It showed increased blood clotting capacity in vitro, as well as increased capacity to bind both red blood cells and platelets, compared to the standard gauze and Merocel®. Finally, a rat-tail amputation model revealed that our SP-CH could even reduce bleeding time in vivo. This work, carried out from a circular economy approach, demonstrates that a green strategy can be followed to manufacture nasal packs using valorized by-products of the food industry, with equal or even better hemostatic properties than the gold standard in the clinic.

Compression Molded Soy Protein Films with Exopolysaccharides Produced by Cider Lactic Acid Bacteria.

Two exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) strains, Liquorilactobacillus (L.) sp CUPV281 and Liquorilactobacillus (L.) mali CUPV271, were isolated from Spanish apple must. Each of the strains produced a dextran, with different branching degrees, to be incorporated into soy protein isolate (SPI) film-forming formulations. Films were prepared by compression molding, a more rapid processing method than solution casting and, thus, with a greater potential for scaling-up production. Thermal analysis showed that SPI and EPS start the degradation process at temperatures above 190 °C, confirming that the compression temperature selected (120 °C) was well below the corresponding degradation temperatures. Resulting films were transparent and homogeneous, as shown by UV-Vis spectroscopy and SEM, indicating the good compatibility between SPI and EPS. Furthermore, FTIR analysis showed that the interactions between SPI and EPS were physical interactions, probably by hydrogen bonding among the polar groups of SPI and EPS. Regarding antifungal/fungistatic activity, LAB strains used in this study showed an inhibitory effect on germination of fungal spores.

The Effect of Cross-Linking with Citric Acid on the Properties of Agar/Fish Gelatin Films.

The aim of this work was to assess the effect of fish gelatin-citric acid nucleophilic substitution and agar-citric acid esterification reactions on the properties of agar/fish gelatin films. Since temperature is an important cross-linking parameter, films were treated at 90 °C and 105 °C and film properties were compared to those of non-cured films. It was observed that temperature favored the aforementioned reactions, which induced physical and morphological changes. In this regard, darker films with a rougher surface were obtained for the films with a higher cross-linking degree. While mechanical properties were slightly modified, the barrier properties were enhanced due to the reactions that occurred. Therefore, these agar/fish gelatin films cross-linked through two different reactions can be considered to be promising materials as active films for different purposes, such as active packaging or pharmaceutical applications.

Valorization of marine-derived biowaste to develop chitin/fish gelatin products as bioactive carriers and moisture scavengers.

Marine-derived biowaste was valorized to develop chitin/fish gelatin porous materials with the aim of being used as moisture scavengers and bioactive carriers. Chitin was extracted from squid pens, abundant and available biowastes from fishery industry, through a sustainable process and the environmental assessment was carried out. Besides the valorization of biowaste, it is worth noting that the use of this specific biowaste allows the avoidance of discoloration and demineralization processes to extract chitin and, thus, a lower consumption of resources, both chemicals and energy, in comparison to the conventional chitin extraction from crustacean shells. Consequently, this alternative source of chitin brings economic and environmental benefits. In addition to the reduction of food waste disposal, the incorporation of squid pen-extracted chitin into fish gelatin formulations led to the conversion of a biowaste into a value-added product. In this regard, chitin was employed as a reinforcing agent in order to improve the mechanical behavior of fish gelatin materials. It is worth noting that good compatibility between gelatin and chitin was achieved since no chitin aggregation was observed. Furthermore, more defined pores were obtained after chitin addition. Additionally, tetrahydrocurcumin was incorporated into the formulation as a bioactive and its release was analyzed during three days. It was observed that samples prepared with chitin and THC showed potential as active porous materials for bioactive delivery.

Electrospinning of Fish Gelatin Solution Containing Citric Acid: An Environmentally Friendly Approach to Prepare Crosslinked Gelatin Fibers.

The majority of the crosslinking approaches employed to confer water resistance properties to electrospun gelatin mats are based on the use of potential cytotoxic agents, turning out to be not suitable for biomedical applications. Environmentally friendly chemical strategies based on the use of non-toxic agents are, therefore, strongly demanded. In the present work, the possibility to produce crosslinked electrospun fish gelatin mats by electrospinning an aqueous solution, containing citric acid as a crosslinking agent, is reported. The effect of pH on solution rheological properties, as well as on the electrospun mat morphology, chemistry, and crosslinking degree, is assessed. The increase of solution pH from 1.8 to 3.7 allows for obtaining fibers that maintain the fibrous morphology also in the mat. Subsequent thermal treatment of the electrospun mat (80 °C for 30 min) turns out to increase the crosslinking degree and morphological stability of the mat.

Development of Bioinspired Gelatin and Gelatin/Chitosan Bilayer Hydrofilms for Wound Healing.

In the current study, we developed a novel gelatin-based bilayer wound dressing. We used different crosslinking agents to confer unique properties to each layer, obtaining a bioinspired multifunctional hydrofilm suitable for wound healing. First, we produced a resistant and non-degradable upper layer by lactose-mediated crosslinking of gelatin, which provided mechanical support and protection to overall design. For the lower layer, we crosslinked gelatin with citric acid, resulting in a porous matrix with a great swelling ability. In addition, we incorporated chitosan into the lower layer to harness its wound healing ability. FTIR and SEM analyses showed that lactose addition changed the secondary structure of gelatin, leading to a more compact and smoother structure than that obtained with citric acid. The hydrofilm was able to swell 384.2 ± 57.2% of its dry weight while maintaining mechanical integrity. Besides, its water vapour transmission rate was in the range of commercial dressings (1381.5 ± 108.6 g/m2·day). In vitro, cytotoxicity assays revealed excellent biocompatibility. Finally, the hydrofilm was analysed through an ex vivo wound healing assay in human skin. It achieved similar results to the control in terms of biocompatibility and wound healing, showing suitable characteristics to be used as a wound dressing.

Extraction and incorporation of bioactives into protein formulations for food and biomedical applications.

Bioactive compounds from natural resources have been pointed out as promising substances with great benefits for human health. Furthermore, new techniques for their extraction have been reviewed in order to consider a global approach taking economic and environmental issues into account. Additionally, the incorporation of these biologically active compounds into protein-based products manufactured via different processing methods, such as solution casting, compression moulding, electrospinning, freeze-drying, and 3D printing, has been assessed, since the design and manufacturing method employed have a direct influence into the final properties of the material. Hence, new opportunities to develop active biopolymeric materials with great potential in food and biomedical applications have been presented. This review aims to provide an overview of some advanced technologies employed for bioactive extraction, as well as the bioactives incorporation into protein formulations to produce biomaterials and food packaging.

Valorisation of blueberry waste and use of compression to manufacture sustainable starch films with enhanced properties.

Blueberry waste from juice processing was valorised to develop starch films by compression moulding. The compression process resulted in hydrophobic films with water contact angles even higher than 100° for the films prepared with the highest blueberry waste content. Additionally, the film solubility was reduced by the incorporation of blueberry waste, regardless of the solution pH. These films also exhibited good barrier properties against UV light due to the aromatic compounds present in the blueberry waste. Furthermore, films showed a homogenous surface, although some pores appeared in the cross-section for the films with the highest blueberry waste content. Results highlighted the use of thermo-mechanical processes such as compression to manufacture sustainable films with enhanced properties through waste valorisation by the techniques actually employed at industrial scale.