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Taking into account that natural polymers are renewable and biodegradable, hybrid materials based on natural polymers are required for advanced technological applications with reduced environmental footprint. In this work, sustainable composites have been developed based on collagen as a polymeric matrix and different magnetic fillers, in order to tailor magnetic response. The composites were prepared by solution casting with 30 wt% of magnetite nanoparticles (Fe 3 O 4 NPs), magnetite nanorods (Fe 3 O 4 NRs) or cobalt ferrite nanoparticles (CoFe 2 O 4 NPs). It is shown that the magnetic filler type has no bearing on the morphology, physical-chemical, or thermal characteristics of the composites, whereas the mechanical properties are determined by the magnetic filler, leading to a reduction in tensile strength, with values of 4.95 MPa for Fe 3 O 4 NPs, 9.20 MPa for Fe 3 O 4 NRs and 5.21 MPa for CoFe 2 O 4 NPs containing samples. However, the highest magnetization saturation is obtained for Fe 3 O 4 NPs (44 emu.g -1 ) and the higher coercive field for CoFe 2 O 4 NPs (2062 Oe). In order to prove functionality of the developed composites, a self-sensing magnetic actuator device has been developed with the composite film with CoFe 2 O 4 NPs, showing high stability over cycling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Coffee wastes are underused materials, largely available in coffee producing regions, which can be used to obtain pectins for the development of films for packaging. Coffee residual water (CRW) provided a phenolic and protein rich-pectic fraction (CRWP), which has 49 % uronic acid. This pectic fraction was used for the development of films with chitosan (Chit). Additionally, pectins extracted from coffee pulp with acid, Coffea arabica pectin (CAP), hot water-soluble pectic fraction (HWSP), and chelating agent-soluble pectic fraction (CSP), were used to develop pectin-chitosan films. Flow and viscoelastic properties of film forming solutions were assessed, showing better characteristics for the pectins from the pulp over those from the residual water. The different composition of the pectin fractions allowed to relate film properties with their structural features and Fourier transform infrared (FTIR) spectroscopy showed interactions between pectin and chitosan in the films. Results showed that CAP-Chit and CSP-Chit films were transparent, hydrophobic, and had the best mechanical properties. These results demonstrate that coffee residual wastes have the potential to provide pectins that can be used for the development of films., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Inks based on soybean protein isolate (SPI) were developed and their formulations were optimized as a function of the ink heat treatment and the content of other biopolymers to assess the effects of protein-polysaccharides and protein-protein interactions. First, the rheological behavior of the inks was analyzed in relation to the polyvinyl alcohol (PVA) concentration employed (20, 25, and 30 wt%) and, as a result of the analysis, the ink with 25 wt% PVA was selected. Additionally, sodium alginate (SA) and gelatin (GEL) were added to the formulations to improve the viscoelastic properties of the inks and the effect of the SA or GEL concentrations (1, 2, and 3 wt%) was studied. All inks showed shear thinning behavior and self-supporting abilities. Among all the 3D printed scaffolds, those with higher SA (3 wt%) or GEL (2 and 3 wt%) content showed higher shape fidelity and were selected for further characterization. Texture profile analysis demonstrated that the scaffolds prepared with previously heat-treated inks containing 3 wt% GEL showed the highest strength. Additionally, these scaffolds showed a higher water-uptake capacity profile.

Edible mealworms can be farmed to produce high-quality nutrients and proteins, useful as ingredients in human and animal foods. During this process biological waste is produced. This work explores the usage of the biological waste as source to produce chitin and chitosan with different potential applications. Different waste fractions were processed, and the feasibility of chitin isolation was assessed. Chitosan was derived, and films were fabricated and tested for intended uses. Data indicate that biopolymers with different properties can be obtained from multiple biological waste fractions. All samples show antibacterial activity, while chitosan films derived from molt show interesting properties for packaging purposes. Films also trigger the expression of anti-inflammatory phenotype markers in macrophage cells, which may be useful for tissue engineering implantation purposes. Altogether, biological waste from insect farming can be used to extract chitin and chitosan with different properties, and therefore, suitable for different applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

With the aim of replacing synthetic macromolecules by biological macromolecules for advanced applications, collagen films were produced with two different ionic liquids (ILs), choline dihydrogen phosphate ([Ch][DHP]) and choline serinate ([Ch][Seri]), added in order to modulate the electrical responses. The films were prepared by casting, varying IL content between 0 and 6 wt%. The morphology and thermal properties of the resulting films were found to be independent of both IL type and content. However, the highest direct curret (d.c.) electrical conductivity (1.4 × 10 -8  S·cm -1 ) was achieved for collagen films containing 3 wt% [Ch][DHP]. Furthermore, it was demonstrated that IL/collagen films were non-cytotoxic, with cell activity values exceeding 70 %. These collagen films were proven to be suitable for force sensing applications, displaying excellent sensitivity and stability upon repeated testing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Chronic wounds are a worldwide problem that affect >40 million people every year. The constant inflammatory status accompanied by prolonged bacterial infections reduce patient's quality of life and life expectancy drastically. An important cell type involved in the wound healing process are mesenchymal stromal cells (MSCs) due to their long-term demonstrated immunomodulatory and pro-regenerative capacity. Thus, in this work, we leveraged and compared the therapeutic properties of MSCs derived from both adipose tissue and hair follicle, which we combined with sponge-like scaffolds (SLS) made of valorized soy protein and β-chitin. In this regard, the combination of these cells with biomaterials permitted us to obtain a multifunctional therapy that allowed high cell retention and growing rates while maintaining adequate cell-viability for several days. Furthermore, this combined therapy demonstrated to increase fibroblasts and keratinocytes migration, promote human umbilical vein endothelial cells angiogenesis and protect fibroblasts from highly proteolytic environments. Finally, this combined therapy demonstrated to be highly effective in reducing wound healing time in vivo with only one treatment change during all the experimental procedure, also promoting a more functional and native-like healed skin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

This work reports on the development of collagen films with graphene oxide nanoparticles (GO NPs), aiming toward the development of a new generation of functional sustainable sensors. For this purpose, different GO NP contents up to 3 wt % were incorporated into a collagen matrix, and morphological, thermal, mechanical and electrical properties were evaluated. Independently of the GO NP content, all films display an increase in thermal stability as a result of the increase in the structural order of collagen, as revealed by XRD analysis. Further, the inclusion of GO NPs into collagen promotes an increase in the intensity of oxygen characteristic absorption bands in FTIR spectra, due to the abundant oxygen-containing functional groups, which lead to an increase in the hydrophilic character of the surface. GO NPs also influence the mechanical properties of the composites, increasing the tensile strength from 33.2 ± 2.4 MPa (collagen) to 44.1 ± 1.0 MPa (collagen with 3 wt % GO NPs). Finally, the electrical conductivity also increases slightly with GO NP content, allowing the development of resistive bending sensors.

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.

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., Competing Interests: The authors declare they have no competing interests., (Copyright:© 2023, Uranga J, Carranza T, Peñalba M, et al.)

Considering the sustainable development goals to reduce environmental impact, sustainable sensors based on natural polymers are a priority as the large im plementation of these materials is required considering the Internet of Things (IoT) paradigm. In this context, the present work reports on sustainable blends based on collagen and different ionic liquids (ILs), including ([Ch][DHP], [Ch][TSI], [Ch][Seri]) and ([Emim][TFSI]), processed with varying contents and types of ILs in order to tailor the electrical response. Varying IL types and contents leads to different interactions with the collagen polymer matrix and, therefore, to varying mechanical, thermal, and electrical properties. Collagen/[Ch][Seri] samples display the most pronounced decrease of the tensile strength (3.2 ± 0.4 MPa) and an increase of the elongation at break (50.6 ± 1.5%). The best ionic conductivity value of 0.023 mS cm -1 has been obtained for the sample with 40 wt % of the IL [Ch][Seri]. The functional response of the collagen-IL films has been demonstrated on a resistive touch sensor whose response depends on the ionic conductivity, being suitable for the next generation of sustainable touch sensing devices., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

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., Competing Interests: The authors declare they have no competing interests., (Copyright:© 2023, Carranza T, Uranga J, Irastorza A, et al.)

Chitosan-pectin films with iron oxide (Fe 3 O 4 ) magnetic nanoparticles were prepared by solution casting in order to produce biopolymer based magnetically active materials. Infrared (FTIR) spectra indicated physical interactions between the matrix and nanoparticles, corroborated by differential scanning calorimetry (DSC) results. In addition, thermal characterization suggested that the interactions between chitosan, pectin and the nanoparticles resulted in a less compact structure, influencing the film mechanical properties. Regarding vibrating-sample magnetometry (VSM) and electrical analysis, chitosan-pectin films with Fe 3 O 4 nanoparticles showed ferrimagnetic behavior, with an increase of the dielectric constant as the nanoparticle concentration increased. Furthermore, films displayed enhanced antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) bacteria. Therefore, chitosan-pectin films with Fe 3 O 4 magnetic nanoparticles provide promising results for active and intelligent food packaging applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

The management of food waste and by-products has become a challenge for the agri-food sector and an example are whey by-products produced in dairy industries. Seeking other whey valorisation alternatives and applications, whey protein films for food packaging applications were developed in this study. Films containing different amounts (0, 5, 10, and 15 wt%) of ascorbic acid were manufactured via compression-moulding and their physicochemical, thermal, barrier, optical, and mechanical properties were analysed and related to the film structure. Additionally, the environmental assessment of the films was carried out to analyse the impact of film manufacture. Regarding physicochemical properties, both FTIR and water uptake analyses showed the presence of non-covalent interactions, such as hydrogen bonding, between whey protein and ascorbic acid as band shifts at the 1500-1700 cm -1 region as well as a water absorption decrease from 380% down to 240% were observed. The addition of ascorbic acid notably improved the UV-Vis light absorbance capacity of whey protein films up to 500 nm, a relevant enhancement for protecting foods susceptible to UV-Vis light-induced lipid oxidation. In relation to the environmental assessment, it was concluded that scaling up film manufacture could lead to a reduction in the environmental impacts, mainly electricity consumption.

Complex scaffolds composed of micro- and nano-structures are a key target in tissue engineering and the combination of sequential 3D printing and electrospinning enables the fabrication of these multi-scale structures. In this work, dual 3D printed and electrospun polycaprolactone (PCL) scaffolds with multiple mesh layers were successfully prepared. The scaffold macro- and micro-porosity were assessed by optical and scanning electron microscopy, showing that electrospun fibers formed aligned meshes within the pores of the scaffold. Consequently, the hydrophilicity of the scaffold increased with time, enhancing cell adhesion and growth. Additionally, compression tests in back and forth cycles demonstrated a good shape recovery behavior of the scaffolds. Biological results indicated that hybrid PCL scaffolds are biocompatible and enable a correct cell culture over time. Moreover, MC3T3-E1 preosteoblast culture on the scaffolds promoted the mineralization, increased the alkaline phosphatase (ALP) activity and upregulated the expression of early and late osteogenic markers, namely ALP and osteopontin (OPN), respectively. These results demonstrate that the sequential combination of 3D printing and electrospinning provides a facile method of incorporating fibers within a 3D printed scaffold, becoming a promising approach towards multi-scale hierarchical scaffolds capable of guiding the osteogenic differentiation.

The wool fibers of the Latxa sheep breed were combined with a soy protein isolate (SPI) matrix to develop sustainable biocomposites with acoustic properties, adding value to Latxa sheep wool, which is currently considered a residue. Samples with 7, 10, 15, and 20 wt % wool were prepared by freeze drying in order to develop porous structures, as shown by SEM analysis. Additionally, XRD analysis provided the evidence of a change toward a more amorphous structure with the incorporation of wool fibers due to the interactions between the soy protein and keratin present in wool fibers, as shown by the relative intensity changes in the FTIR bands. The biocomposites were analyzed in a Kundt's tube to obtain their sound absorption coefficient at normal incidence. The results showed an acoustic absorption coefficient that well-surpassed 0.9 for frequencies above 1000 Hz. This performance is comparable to that of the conventional synthetic materials present in the market and, thus, sheep wool/SPI biocomposites are suitable to be used as acoustic absorbers in the building industry, highlighting the potential of replacing not only synthetic fibers but also synthetic polymers, with natural materials to enhance the sustainability of the building sector.

309Sterilization is a crucial step in the process of developing bioinks for tissue engineering applications. In this work, alginate/gelatin inks were subjected to three sterilization methods: ultraviolet (UV) radiation, filtration (FILT), and autoclaving (AUTO). In addition, to simulate the sterilization effect in a real environment, inks were formulated in two different media, specifically, Dulbecco's Modified Eagle's Medium (DMEM) and phosphate-buffered saline (PBS). First, rheological tests were performed to evaluate the flow properties of the inks, and we observed that UV samples showed shear thinning behavior, which was favorable for three-dimensional (3D) printing. Furthermore, the 3D-printed constructs developed with UV inks showed better shape and size fidelity than those obtained with FILT and AUTO. In order to relate this behavior to the material structure, Fourier transform infrared (FTIR) analysis was carried out and the predominant conformation in protein was determined by deconvolution of the amide I band, which confirmed that the prevalence of a-helix structure was greater for UV samples. This work highlights the relevance of sterilization processes, which are essential for biomedical applications, in the research field of bioinks., Competing Interests: The authors declare no conflicts of interest., (Copyright: © 2022 Carranza, et al.)

Red grape pomace was used as a source for poly(3-hydroxybutyrate) (PHB) production, which was then subject to a range of purification processes. The different PHB biopolymers were characterized for chemical structure, crystallinity, thermal properties, colour, release of compounds into different food simulants and antioxidant inhibition, and comparisons were made with a commercially available PHB. An increase in purification steps did not have a significant effect on the high thermal stability of the extracted biopolymer, but it decreased the degree of crystallinity and the presence of amino acids and aromatic compounds. With additional purification, the PHB powders also whitened and the number of components released from the biopolymer into food simulants decreased. The released compounds presented antioxidant inhibition, which has not been previously reported in the literature or with commercially available polyhydroxyalkanoates. This is of great interest for food packaging and biomedical industries where the addition of antioxidant additives to improve PHB functional properties may not be necessary and could be avoided., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Blend films from chicken protein isolate (CPI) and fish skin gelatin (FSG) at various CPI/FSG ratios (100:0, 80:20, 70:30, 60:40, 0:100), prepared at pH 3 or 11 were characterized. At the same pH, tensile strength (TS) of CPI/FSG films was higher than CPI and FSG films, and CPI/FSG film (60:40) had highest TS. Moreover, elongation at break (EAB) of blend films increased as FSG content augmented. EAB of CPI film and CPI/FSG (80:20) film was similar for both pHs. CPI films generally possessed higher water vapor permeability (WVP), light barrier property and b *-value than FSG counterpart. CPI films prepared at both pHs were not sealable. Nevertheless, addition of FSG improved sealing ability of blend films. At the same CPI/FSG ratio, seal strength and seal efficiency were lower for films prepared at pH 11. Moreover, higher TS and b *-value were gained, compared to those of films prepared at pH 3. Less cracks on surface and cross-section appeared for CPI/FSG films as revealed by scanning electron microscopy images, compared to CPI and FSG films. Therefore, incorporation of FSG up to 40% into blend film was able to improve mechanical properties, WVP, and sealing ability of blend films., Competing Interests: Conflict of interestThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© Association of Food Scientists & Technologists (India) 2021.)

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 β-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., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)

Chitosan-pectin hydrogels were prepared, and their rheological properties were assessed in order to select the best system to develop scaffolds by 3D printing. Hydrogels showed a weak gel behavior with shear thinning flow properties, caused by the physical interactions formed between both polysaccharides, as observed by FTIR analysis. Since systems with high concentration of pectin showed aggregations, the system composed of 2 wt% chitosan and 2 wt% pectin (CHI2PEC2) was selected for 3D printing. 3D printed scaffolds showed good shape accuracy, and SEM and XRD analyses revealed a homogeneous and amorphous structure. Moreover, scaffolds were stable and kept their shape and size after a cycle of compression sweeps. Their integrity was also maintained after immersion in PBS at 37 °C, showing a high swelling capacity, suitable for exudate absorption in wound healing applications.

Native collagen doughs were processed using a syringe-based extrusion 3D printer to obtain collagen scaffolds. Before processing, the rheological properties of the doughs were analyzed to determine the optimal 3D printing conditions. Samples showed a high shear-thinning behavior, reported beneficial in the 3D printing process. In addition, tetrahydrocurcumin (THC) was incorporated into the dough formulation and its effect on collagen structure, as well as the resulting scaffold's suitability for wound healing applications, were assessed. The denaturation peak observed by differential scanning calorimetry (DSC), along with the images of the scaffolds' surfaces assessed using scanning electron microscopy (SEM), showed that the fibrillar structure of collagen was maintained. These outcomes were correlated with X-ray diffraction (XRD) results, which showed an increase of the lateral packaging of collagen chains was observed in the samples with a THC content up to 4%, while a higher content of THC considerably decreased the structural order of collagen. Furthermore, physical interactions between collagen and THC molecules were observed using Fourier transform infrared (FTIR) spectroscopy. Additionally, all samples showed swelling and a controlled release of THC. These results along with the mucoadhesive properties of collagen suggested the potential of these THC-collagen scaffolds as sustained THC delivery systems.

Extrusion bioprinting based on the development of novel bioinks offers the possibility of manufacturing clinically useful tools for wound management. In this study, we show the rheological properties and printability outcomes of two advanced dressings based on platelet-rich plasma (PRP) and platelet-poor plasma (PPP) blended with alginate and loaded with dermal fibroblasts. Measurements taken at 1 h, 4 days, and 18 days showed that both the PRP- and PPP-based dressings retain plasma and platelet proteins, which led to the upregulation of angiogenic and immunomodulatory proteins by embedded fibroblasts (e.g., an up to 69-fold increase in vascular endothelial growth factor (VEGF), an up to 188-fold increase in monocyte chemotactic protein 1 (MCP-1), and an up to 456-fold increase in hepatocyte growth factor (HGF) 18 days after printing). Conditioned media harvested from both PRP and PPP constructs stimulated the proliferation of human umbilical vein endothelial cells (HUVECs), whereas only those from PRP dressings stimulated HUVEC migration, which correlated with the VEGF/MCP-1 and VEGF/HGF ratios. Similarly, the advanced dressings increased the level of interleukin-8 and led to a four-fold change in the level of extracellular matrix protein 1. These findings suggest that careful selection of plasma formulations to fabricate wound dressings can enable regulation of the molecular composition of the microenvironment, as well as paracrine interactions, thereby improving the clinical potential of dressings and providing the possibility to tailor each composition to specific wound types and healing stages.

Thermocompression was employed to prepare citric acid-crosslinked chitosan films with Aloe vera (AV) as bioactive compound. Films were easy to handle and mechanical properties did not change with the addition of AV up to 10 wt%, although both TS and EAB decreased for the films with 15 wt% AV, indicating that high AV contents would hinder intermolecular interactions among the formulation components. Maillard reaction occurred between chitosan and citric acid at the processing temperature used (115 °C), while physical interactions took place with AV, as shown by FTIR analysis. All films were insoluble but displayed hydration and limited swelling due to both physical and chemical interactions promoted by AV and citric acid, respectively. A slow AV release, governed by a Fickian diffusion controlled mechanism, and an increase of surface hydrophilicity, which favors cell adhesion, were observed., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The vision impairments suffered by millions of people worldwide and the shortage of corneal donors show the need of substitutes that mimic native tissue to promote cell growth and subsequent tissue regeneration. The current study focused on the in vitro assessment of protein-based biomaterials that could be a potential source for corneal scaffolds. Collagen, soy protein isolate (SPI), and gelatin films cross-linked with lactose or citric acid were prepared and physicochemical, transmittance, and degradation measurements were carried out. In vitro cytotoxicity, cell adhesion, and migration studies were performed with human corneal epithelial (HCE) cells and 3T3 fibroblasts for the films' cytocompatibility assessment. Transmittance values met the cornea's needs, and the degradation profile revealed a progressive biomaterials' decomposition in enzymatic and hydrolytic assays. Cell viability at 72 h was above 70% when exposed to SPI and gelatin films. Live/dead assays and scanning electron microscopy (SEM) analysis demonstrated the adhesion of both cell types to the films, with a similar arrangement to that observed in controls. Besides, both cell lines were able to proliferate and migrate over the films. Without ruling out any material, the appropriate optical and biological properties shown by lactose-crosslinked gelatin film highlight its potential for corneal bioengineering.

Protein-based conductive materials are gaining attention as alternative components of electronic devices for value-added applications. In this regard, soy protein isolate (SPI) was processed by extrusion in order to obtain SPI pellets, subsequently molded into SPI films by hot pressing, resulting in homogeneous and transparent films, as shown by scanning electron microscopy and UV-vis spectroscopy analyses, respectively. During processing, SPI denatured and refolded through intermolecular interactions with glycerol, causing a major exposition of tryptophan residues and fluorescence emission, affecting charge distribution and electron transport properties. Regarding electrical conductivity, the value found (9.889 × 10 -4 S/m) is characteristic of electrical semiconductors, such as silicon, and higher than that found for other natural polymers. Additionally, the behavior of the films in contact with water was analyzed, indicating a controlled swelling and a hydrolytic surface, which is of great relevance for cell adhesion and spreading. In fact, cytotoxicity studies showed that the developed SPI films were biocompatible, according to the guidelines for the biological evaluation of medical devices. Therefore, these SPI films are uniquely suited as bioelectronics because they conduct both ionic and electronic currents, which is not accessible for the traditional metallic conductors.

Collagen was obtained from porcine skin by mechanical pretreatments with the aim of preserving the triple helix structure of native collagen, which was indirectly corroborated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) results. Moreover, aloe vera (AV), with inherent biological properties, was incorporated into collagen film formulations, and films were prepared by compression and characterized to assess their suitability for biomedical applications. SEM images showed that the fibrillar structure of collagen changed to a rougher structure with the addition of AV, in accordance with the decrease in the lateral packaging of collagen chains observed by XRD analysis. These results suggested interactions between collagen and AV, as observed by FTIR. Considering that AV content higher than 20 wt % did not promote further interactions, this formulation was employed for biological assays and the suitability of AV/collagen films developed for biomedical applications was confirmed.

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.

Two Alteromonas sp. strains isolated from deep seawater were grown to promote the production of exopolysaccharides (EPS, E611 and E805), which were incorporated into chitosan solutions to develop films. The combination of the major marine polysaccharides (chitosan and the isolated bacterial EPS) resulted in the formation of homogenous, transparent, colorless films, suggesting good compatibility between the two components of the film-forming formulation. With regards to optical properties, the films showed low values of gloss, in the range of 5-10 GU, indicating the formation of non-glossy and rough surfaces. In addition to the film surface, both showed hydrophobic character, with water contact angles higher than 100 º, regardless of EPS addition. Among the two EPS under analysis, chitosan films with E805 showed better mechanical performance, leading to resistant, flexible, easy to handle films.

Native collagen scaffolds were prepared in this work, in which both materials and environmental approaches were considered with the aim of providing a global strategy towards more sustainable biomaterials. From the environmental perspective, it is worth mentioning that acid and enzymatic treatments have been avoided to extract collagen, allowing the reduction in the use of resources, in terms of chemicals, energy, and time, and leading to a low environmental load of this step in all the impact categories under analysis. With the incorporation of chitosan into the scaffold-forming formulations, physical interactions occurred between collagen and chitosan, but the native collagen structure was preserved, as observed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses. The incorporation of chitosan also led to more homogenous porous microstructures, with higher elastic moduli and compression resistance for both dry and hydrated scaffolds. Furthermore, hydrated scaffolds preserved their size and shape after some compression cycles.

Chitosan/collagen films were developed and characterized in order to assess the suitability of these films for biomedical applications. Hence, physicochemical, thermal, barrier and mechanical properties were analyzed and related to the film structure, which showed the prevalence of the triple helix of native collagen after the addition of chitosan. Furthermore, collagen fiber diameter changed from 3.9 ± 0.6 μm, for collagen films without chitosan, to 1.8 ± 0.5 μm, for collagen films with low molecular weight chitosan. These results suggested interactions between collagen and chitosan molecules, as observed by Fourier transform infrared (FTIR) analysis. Regarding film barrier properties, chitosan/collagen films showed a water vapor transmission rate around 1174 g m -2  day -1 , suitable for biomedical applications such as wound healing. Additionally, biological tests confirmed that the chitosan/collagen films developed are suitable for biomedical applications., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., Competing Interests: The authors declare no conflict of interest.

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

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.

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.

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/m 2 ·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.

The aim of this work was to extract phenolic compounds from Chardonnay grape marc employing a microwave-assisted extraction (MAE). Firstly, the effect of solvent concentration (30-60%), solid mass (1.0-2.0 g) and extraction time (5-15 min) on the recovery of phenolic content and antioxidant capacity was evaluated using a response surface methodology (RSM). The optimal parameters found by RSM were 48% ethanol for the solvent content, 10 min for the extraction time, and 1.77 g for the solid mass. The extraction was carried out at room temperature to increase scaling-up opportunities at industrial level. It was found that the phenolic profile was mainly composed of flavanols, such as procyanidins, catechin and epicatechin. Furthermore, the polyphenols obtained by MAE showed a DPPH· inhibition value of 87 ± 5% and the total phenolic content was 1.21 ± 0.04 mg GAE/mL. Finally, it was observed that the degradation temperature of the extract (≈ 200 °C) was above the temperature commonly used for the manufacture of protein films by thermo-mechanical processes. This highlights the potential use of this extract as a bioactive additive in protein film forming formulations for food and pharmaceutical applications., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

An alternative approach towards more sustainable chitosan films, through their manufacture by thermo-compression molding, was explore in this work. This strategy permitted the reduction of production times and avoided the use of organic solvents since biopolymer and acid were mixed in their solid form. Furthermore, the acid used as a crosslinker was citric acid, a natural policarboxylic acid, which promoted the reaction with chitosan, as shown by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). This crosslinking reaction led to the formation of homogeneous structures, as observed by scanning electron microscopy (SEM), indicating a good compatibility among all the components of the mixture and enhancing the mechanical properties of the resulting films. In particular, an increase of 80% for tensile strength and an increase of 3000% for elongation at break were observed for the crosslinked films. In addition to the homogeneous surface of citric acid-incorporated films, all the films showed hydrophobic character and the addition of citric acid led to a more amorphous structure. In sum, citric acid-incorporated chitosan films manufactured by compression molding were found to show potential for food and pharmaceutical applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, a response surface methodology (RSM) using a Box-Behnken design was applied to optimize the mechanical response (tensile strength, elongation at break and Young's modulus) of fish gelatin films. These responses were analyzed as a function of glycerol content (0-10% on gelatin basis), added as a plasticizer, gallic acid content (5-15% on gelatin basis), used as crosslinker, and solution pH (4.5-10). Second order polynomial models were adjusted for the three responses, and they were found to be reliable according to the standard statistical analysis. The values of the independent factors that maximize the responses were also determined. In order to relate mechanical performance to material structure, Fourier transform infrared (FTIR) analysis was carried out and this revealed that a reaction occurs between gelatin and gallic acid through a process that releases water and provides a plasticizing effect. The performed time-, material- and cost-saving optimization of the formulation based on biodegradable compounds from abundant renewable resources enabled a sustainable approach to the development of new materials., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Tetrahydrocurcumin (THC) is one of the major colourless metabolites of curcumin and shows even greater pharmacological and physiological benefits. The aim of this work was the manufacturing of porous scaffolds as a carrier of THC under physiological conditions. Fish-derived gelatin scaffolds were prepared by freeze-drying by two solutions concentrations (2.5% and 4% w/v), cross-linked via addition of lactose and heat-treated at 105 °C. This cross-linking reaction resulted in more water resistant scaffolds with a water uptake capacity higher than 800%. Along with the cross-linking reaction, the gelatin concentration affected the scaffold morphology, as observed by scanning electron microscopy images, by obtaining a reduced porosity but larger pores sizes when the initial gelatin concentration was increased. These morphological changes led to a scaffold's strength enhancement from 0.92 ± 0.22 MPa to 2.04 ± 0.18 MPa when gelatin concentration was increased. THC release slowed down when gelatin concentration increased from 2.5 to 4% w/v, showing a controlled profile within 96 h. Preliminary in vitro test with chondrocytes on scaffolds with 4% w/v gelatin offered higher metabolic activities and cell survival up to 14 days of incubation. Finally the addition of THC did not influence significantly the cytocompatibility and potential antibacterial properties were demonstrated successfully against Staphylococcus aureus., (Copyright © 2018 Elsevier B.V. All rights reserved.)

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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this work, the effect of hydrolyzed keratin on the properties of soy protein-based films was analyzed when different manufacture processes were employed. It is widely known that the processing method selected can affect the film properties as a function of the structure obtained during the film formation. Therefore, the assessment of hydrolyzed keratin/soy protein films processed by casting and compression moulding was carried out by means of the analysis of physicochemical, thermal, mechanical, optical and surface properties. It was observed that the incorporation of hydrolyzed keratin, obtained from a simpler, environmentally friendlier and more sustainable extraction method, resulted in the improvement of the thermal stability of the films, irrespective of the processing method employed. Moreover, the films processed by compression moulding showed enhanced tensile strength, which increased with the incorporation of hydrolyzed keratin due to the formation of disulfide bonds., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This work is focused on the development of renewable and biodegradable films by the valorisation of wastes from food processing industries, with the aim of contributing to the development of more sustainable films. In this context, different contents of blueberry pomace (BP) were incorporated into cassava starch (CS) film forming solutions and the functional properties of the films prepared by solution casting were investigated, specifically, thermal, optical and physicochemical properties. BP-incorporated films showed good barrier properties against light, indicating their beneficial effect to prevent food deterioration caused by UV radiation when these films are used for food packaging applications. These results were related to the presence of aromatic compounds in BP, which can absorb light at wavelengths below 300nm. Furthermore, all films maintained their structural integrity after immersion in water (24h) and the maximum swelling displayed was lower than 300%. Additionally, the release of active compounds from BP into food simulants (after 10days) showed higher migration into the acetic acid medium in comparison with the ethanol medium. Therefore, the incorporation of BP into CS film forming solution resulted in the improvement of film performance, suggesting the potential application of these films as active packaging., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Chitin is one of the most abundant natural polysaccharides in the world and it is mainly used for the production of chitosan by a deacetylation process. Chitosan is a bioactive polymer with a wide variety of applications due to its functional properties such as antibacterial activity, non-toxicity, ease of modification, and biodegradability. This review summarizes the most common chitosan processing methods and highlights some applications of chitosan in various industrial and biomedical fields. Finally, environmental concerns of chitosan-based films, considering the stages from raw materials extraction up to the end of life after disposal, are also discussed with the aim of finding more eco-friendly alternatives., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study focuses on the development and characterization of an ultra thin hydro-film based on lactose-mediated crosslinking of fish gelatin by Maillard reaction. Lactose results in the only efficient crosslinker able to produce resistant to handling hydro-films when compared to conventional crosslinkers such as glutaraldehyde or genipin (tested at 25 and 37°C in phosphate buffer saline solution (PBS)).The disappearance of the peak related to the N-containing groups (XPS) and the images obtained by SEM and AFM demonstrate the highly ordered nano-scaled structure of lactose-crosslinked gelatin, confirming the crosslinking efficiency. This dressing presents high hydrophilicity and mild occlusivity, as shown by the swelling curve (max swelling at 5min) and by the occlusion factor of 25.17±0.99%, respectively. It demonstrates high stability to hydrolysis or cell-mediated degradation. Moreover, ISO 10993-5:2009 biocompatibility assay results in undetectable cytotoxicity effects. Spreading, adhesion and proliferation assays confirm the excellent adaptability of the cells onto the hydro-film surface without invading the dressing. Finally, the hydro-film enables the controlled delivery of therapeutic factors, such as the epidermal growth factor (EGF). This study demonstrates that lactose-mediated crosslinking is able to produce ultra thin gelatin hydro-films with suitable properties for biomedical applications, such as wound healing., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Agar/soy protein biocomposite films were successfully processed by extrusion and compression moulding, obtaining transparent and homogeneous films. The conformational changes occurred during the extrusion process and the effect of agar on the final properties were analyzed. As shown by differential scanning calorimetry (DSC) and specific mechanical energy (SME) values, during the extrusion process protein denatured and unfolded protein chains could interact with agar. These interactions were analyzed by Fourier transform infrared spectroscopy (FTIR) and the secondary structure was determined from the amide I band. Those interactions were supported by the decrease of film solubility. Furthermore, the good compatibility between agar and soy protein was confirmed by the images from scanning electron microscopy (SEM)., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Soy protein-based blends were processed by double screw extrusion and the effects of different types and contents of polysaccharides were analyzed. Although extrusion has not been widely used for this type of blends, in this study it was observed that the increase in polysaccharide content in blends caused a decrease in specific mechanical energy (SME), facilitating extrusion process and showing the potential of this process, which is more cost effective at industrial scale. In order to explain this behavior, infrared spectroscopy analysis was carried out, mainly in the amide I and II regions. Moreover, curve fitting analysis showed the conformational changes produced in the blends due to the addition of polysaccharides, which affected protein denaturation. These changes also affected properties such as moisture content (MC) and total solubility matter (TSM). However, conformational changes did not show significant effects with respect to piece density (PD) or in the expansion ratio (ER) of the pellets. The quantitative analysis of the changes in the amide I and II regions provided novel information about the modifications produced in protein-based blends modified with polysaccharides. In this context, infrared spectroscopy provided a convenient and powerful means to monitor interactions between all ingredients used in the blend formulation, which is of great importance in order to explain changes in the functional properties of biodegradable materials used for industrial applications in food and pharmaceutical industries., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The chemical structure of the agar obtained from Gelidium sesquipedale (Rhodophyta) has been determined by (13)C nuclear magnetic resonance ((13)C NMR) and Fourier transform infrared spectroscopy (FTIR). Agar (AG) films with different amounts of soy protein isolate (SPI) were prepared using a thermo-moulding method, and transparent and hydrophobic films were obtained and characterized. FTIR analysis provided a detailed description of the binding groups present in the films, such as carboxylic, hydroxyl and sulfonate groups, while the surface composition was examined using X-ray photoelectron spectroscopy (XPS). The changes observed by FTIR and XPS spectra suggested interactions between functional groups of agar and SPI. This is a novel approach to the characterization of agar-based films and provides knowledge about the compatibility of agar and soy protein for further investigation of the functional properties of biodegradable films based on these biopolymers., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Chitosan-based films plasticized with glycerol were prepared by casting with the aim to obtain environmentally friendly materials for packaging applications. Different contents of glycerol were incorporated into chitosan solutions to improve mechanical properties and all films obtained were flexible and transparent. It was observed that the transparency and good behaviour of the films against UV radiation were not affected by chitosan molecular weight or glycerol content. Moreover, chitosan-based films exhibited excellent barrier properties against water vapour and oxygen, even with the addition of glycerol. The effect of the plasticizer on the properties has been explained using Fourier transform infrared (FTIR) spectroscopic analysis. The changes observed in the intensity of the bands showed that glycerol interacts with chitosan, which could be confirmed by total soluble matter (TSM)., (Copyright © 2012 Elsevier Ltd. All rights reserved.)