Increased mass manufacturing and the pervasive use of plastics in many facets of daily life have had detrimental effects on the environment. As a result, these worries heighten the possibility of climate change due to the carbon dioxide emissions from burning conventional, non-biodegradable polymers. Accordingly, biodegradable gelatin and chitosan polymers are being created as a sustainable substitute for non-biodegradable polymeric materials in various applications. Chitosan is the only naturally occurring cationic alkaline polysaccharide, a well-known edible polymer derived from chitin. The biological activities of chitosan, such as its antioxidant, anticancer, and antimicrobial qualities, have recently piqued the interest of researchers. Similarly, gelatin is a naturally occurring polymer derived from the hydrolytic breakdown of collagen protein and offers various medicinal advantages owing to its unique amino acid composition. In this review, we present an overview of recent studies focusing on applying chitosan and gelatin polymers in various fields. These include using gelatin and chitosan as food packaging, antioxidants and antimicrobial properties, properties encapsulating biologically active substances, tissue engineering, microencapsulation technology, water treatment, and drug delivery. This review emphasizes the significance of investigating sustainable options for non-biodegradable plastics. It showcases the diverse uses of gelatin and chitosan polymers in tackling environmental issues and driving progress across different industries.

Salmon backbones make up about 10 % of the total fish weight and contain valuable proteins, collagen and lipids that can be used for marine ingredients production. Gelatine is derived from the collagen fraction and this study evaluated how different fractionation and extraction procedures can affect the yield and composition of extracted gelatine. Fractionation by mild thermal treatment of backbones (10 min in 40-42 °C) leads to structural changes of muscle, which improves separation of meat from bones and gives better yield of de-muscled backbone fractionation compared to mechanical meat removal. The highest yield of the gelatine (9.3 ± 0.3g dry gelatine from 100g de-muscled backbone dry material) was obtained from mechanically de-muscled backbones. De-muscled backbones were pre-treated with alkaline (0.04 N NaOH) followed by EDTA and 10 % ethanol for de-calcification and lipid extraction, respectively. Gelatine from pretreated backbones was extracted with 60 °C water. The amount of gelatine amino acids (sum of hydroxyproline, proline and glycine) was 43.4 ± 0.2 % of all amino acids in the gelatine. Extracted backbone gelatines showed film-forming ability. Gelatine films were obtained by casting procedure. Resulted salmon backbone 6 % gelatine and 30 % sorbitol films showed properties (e.g. water vapour permeability, colour difference, transparency value) similar to films obtained with commercial gelatine, indicating the capability of the extracted gelatines for its valorisation as edible coatings or bio-based film layers in packaging.

This study investigated the effects of ultrasound treatment or calcium chloride (CaCl2) addition on the physical properties of jelly formulations. Elastic modulus (G\'), loss modulus (G\"), tan δ, shear modulus, yield stress (τ0), phase angle (δ), and gel strength were the parameters selected to describe the requirements of jelly printing, such as fidelity, shape retention, and extrudability. Ultrasound treatment of the jelly formulation without pectin increased the G\' and shear moduli values, while decreasing the δ and gel strength. The addition of CaCl2 to the jelly formulation with pectin increased the G\', G\", shear modulus, τ0, and gel strength but lowered the tan δ and δ values. Both ultrasound treatment and CaCl2 addition improved the jelly printing requirements and demonstrated the potential to control the physical properties of jelly formulations for 3D printing using fused deposition modeling.

Current sprayable hydrogel masks lack the stepwise protection, cleansing, and nourishment of extensive wounds, leading to delayed healing with scarring. Here, we develop a sprayable biomimetic double wound mask (BDM) with rapid autophasing and hierarchical programming for scarless wound healing. The BDMs comprise hydrophobic poly (lactide-co-propylene glycol-co-lactide) dimethacrylate (PLD) as top layer and hydrophilic gelatin methacrylate (GelMA) hydrogel as bottom layer, enabling swift autophasing into bilayered structure. After photocrosslinking, BDMs rapidly solidify with strong interfacial bonding, robust tissue adhesion, and excellent joint adaptiveness. Upon implementation, the bottom GelMA layer could immediately release calcium ion for rapid hemostasis, while the top PLD layer could maintain a moist, breathable, and sterile environment. These traits synergistically suppress the inflammatory tumor necrosis factor-α pathway while coordinating the cyclic guanosine monophosphate/protein kinase G-Wnt/calcium ion signaling pathways to nourish angiogenesis. Collectively, our BDMs with self-regulated construction of bilayered structure could hierarchically program the healing progression with transformative potential for scarless wound healing.

Biomaterial wound dressings, such as hydrogels, interact with host cells to regulate tissue repair. This study investigates how crosslinking of gelatin-based hydrogels influences immune and stromal cell behavior and wound healing in female mice. We observe that softer, lightly crosslinked hydrogels promote greater cellular infiltration and result in smaller scars compared to stiffer, heavily crosslinked hydrogels. Using single-cell RNA sequencing, we further show that heavily crosslinked hydrogels increase inflammation and lead to the formation of a distinct macrophage subpopulation exhibiting signs of oxidative activity and cell fusion. Conversely, lightly crosslinked hydrogels are more readily taken up by macrophages and integrated within the tissue. The physical properties differentially affect macrophage and fibroblast interactions, with heavily crosslinked hydrogels promoting pro-fibrotic fibroblast activity that drives macrophage fusion through RANKL signaling. These findings suggest that tuning the physical properties of hydrogels can guide cellular responses and improve healing, offering insights for designing better biomaterials for wound treatment.

Pressure ulcers (PU) are caused by persistent long-term pressure, which compromises the integrity of the epidermis, dermis, and subcutaneous adipose tissue layer by layer, making it difficult to heal. Platelet products such as platelet lysate (PL) can promote tissue regeneration by secreting numerous growth factors based on clinical studies on skin wound healing. However, the components of PL are difficult to retain in wounds. Gelatin methacrylate (GelMA) is a photopolymerizable hydrogel that has lately emerged as a promising material for tissue engineering and regenerative medicine. The PL liquid was extracted, flow cytometrically detected for CD41a markers, and evenly dispersed in the GelMA hydrogel to produce a surplus growth factor hydrogel system (PL@GM). The microstructure of the hydrogel system was observed under a scanning electron microscope, and its sustained release efficiency and biological safety were tested in vitro. Cell viability and migration of human dermal fibroblasts, and tube formation assays of human umbilical vein endothelial cells were applied to evaluate the ability of PL to promote wound healing and regeneration in vitro. Real-time polymerase chain reaction (PCR) and western blot analyses were performed to elucidate the skin regeneration mechanism of PL. We verified PL\'s therapeutic effectiveness and histological analysis on the PU model. PL promoted cell viability, migration, wound healing and angiogenesis in vitro. Real-time PCR and western blot indicated PL suppressed inflammation and promoted collagen I synthesis by activating STAT3. PL@GM hydrogel system demonstrated optimal biocompatibility and favorable effects on essential cells for wound healing. PL@GM also significantly stimulated PU healing, skin regeneration, and the formation of subcutaneous collagen and blood vessels. PL@GM could accelerate PU healing by promoting fibroblasts to migrate and secrete collagen and endothelial cells to vascularize. PL@GM promises to be an effective and convenient treatment modality for PU, like chronic wound treatment.

Ballistic impacts on human thorax without penetration can produce severe injuries or even death of the carrier. Soft tissue finite element models must capture the non-linear elasticity and strain-rate dependence to accurately estimate the dynamic human mechanical response. The objective of this work is the calibration of a visco-hyperelastic model for soft tissue simulants. Material model parameters have been calculated by fitting experimental stress-strain relations obtained from the literature using genetic algorithms. Several parametric analyses have been carried out during the definition of the optimization algorithm. In this way, we were able to study different optimization strategies to improve the convergence and accuracy of the final result. Finally, the genetic algorithm has been applied to calibrate two different soft tissue simulants: ballistic gelatin and styrene-ethylene-butylene-styrene. The algorithm is able to calculate the constants for visco-hyperelastic constitutive equations with high accuracy. Regarding synthetic stress-strain curves, a short computational time has been shown when using the semi-free strategy, leading to high precision results in stress-strain curves. The algorithm developed in this work, whose code is included as supplementary material for the reader use, can be applied to calibrate visco-hyperelastic parameters from stress-strain relations under different strain rates. The semi-free relaxation time strategy has shown to obtain more accurate results and shorter convergence times than the other strategies studied. It has been also shown that the understanding of the constitutive models and the complexity of the stress-strain objective curves is crucial for the accuracy of the method.

BACKGROUND: Human mesenchymal stem cells originating from umbilical cord matrix are a promising therapeutic resource, and their differentiated cells are spotlighted as a tissue regeneration treatment. However, there are limitations to the medical use of differentiated cells from human umbilical cord matrix-mesenchymal stem cells (hUCM-MSCs), such as efficient differentiation methods.
METHODS: To effectively differentiate hUCM-MSCs into hepatocyte-like cells (HLCs), we used the ROCK inhibitor, fasudil, which is known to induce endoderm formation, and gelatin, which provides extracellular matrix to the differentiated cells. To estimate a differentiation efficiency of early stage according to combination of gelatin and fasudil, transcription analysis was conducted. Moreover, to demonstrate that organelle states affect differentiation, we performed transcription, tomographic, and mitochondrial function analysis at each stage of hepatic differentiation. Finally, we evaluated hepatocyte function based on the expression of mRNA and protein, secretion of albumin, and activity of CYP3A4 in mature HLCs.
RESULTS: Fasudil induced endoderm-related genes (GATA4, SOX17, and FOXA2) in hUCM-MSCs, and it also induced lipid droplets (LDs) inside the differentiated cells. However, the excessive induction of LDs caused by fasudil inhibited mitochondrial function and prevented differentiation into hepatoblasts. To prevent the excessive LDs formation, we used gelatin as a coating material. When hUCM-MSCs were induced into hepatoblasts with fasudil on high-viscosity (1%) gelatin-coated dishes, hepatoblast-related genes (AFP and HNF4A) showed significant upregulation on high-viscosity gelatin-coated dishes compared to those treated with low-viscosity (0.1%) gelatin. Moreover, other germline cell fates, such as ectoderm and mesoderm, were repressed under these conditions. In addition, LDs abundance was also reduced, whereas mitochondrial function was increased. On the other hand, unlike early stage of the differentiation, low viscosity gelatin was more effective in generating mature HLCs. In this condition, the accumulation of LDs was inhibited in the cells, and mitochondria were activated. Consequently, HLCs originated from hUCM-MSCs were genetically and functionally more matured in low-viscosity gelatin.
CONCLUSIONS: This study demonstrated an effective method for differentiating hUCM-MSCs into hepatic cells using fasudil and gelatin of varying viscosities. Moreover, we suggest that efficient hepatic differentiation and the function of hepatic cells differentiated from hUCM-MSCs depend not only on genetic changes but also on the regulation of organelle states.

Electroconductive polymers are the materials of interest for the fabrication of electro-conductive tissues. Metal ions through the redox systems offer polymers with electrical conductivity. In this study, we processed a gelatin methacrylate (GelMA) network with gold nanoparticles (GNPs) through a redox system with parahydroxybenzaldehyde (PHB) or curcumin to enhance its electrical conductivity. Induction of the redox system with both PHB and curcumin into the GelMA, introduced some new functional groups into the polymeric network, as it has been confirmed by H-NMR and FTIR. These new bonds resulted in higher electro-conductivity when GNPs were added to the polymer. Higher electroactivity was achieved by PHB compared to the curcumin-induced redox system, and the addition of GNPs without redox system induction showed the lowest electroactivity. MTT was used to evaluate the biocompatibility of the resultant polymers, and the PHB-treated hydrogels showed higher proliferative effects on the cells. The findings of this study suggest that the introduction of a redox system by PHB in the GelMA network along with GNPs can contribute to the electrochemical properties of the material. This electroactivity can be advantageous for tissue engineering of electro-conductive tissues like cardiac and nervous tissues.

The proficient handling of diabetic wounds, a rising issue coinciding with the global escalation of diabetes cases, poses significant clinical difficulties. A range of biofunctional dressings have been engineered and produced to expedite the healing process of diabetic wounds. This study proposes a multifunctional hydrogel dressing for diabetic wound healing, which is composed of Polyvinyl Alcohol (PVA) and N1-(4-boronobenzyl)-N3-(4-boronophenyl)-N1, N1, N3, N3-teramethylpropane-1, 3-diaminium (TSPBA), and a dual-drug loaded Gelatin methacryloyl (GM) microgel. The GM microgel is loaded with sodium fusidate (SF) and nanoliposomes (LP) that contain metformin hydrochloride (MH). Notably, adhesive and self-healing properties the hydrogel enhance their therapeutic potential and ease of application. In vitro assessments indicate that SF-infused hydrogel can eliminate more than 98% of bacteria within 24 h and maintain a sustained release over 15 days. Additionally, MH incorporated within the hydrogel has demonstrated effective glucose level regulation for a duration exceeding 15 days. The hydrogel demonstrates a sustained ability to neutralize ROS throughout the entire healing process, predominantly by electron donation and sequestration. This multifunctional hydrogel dressing, which integrated biological functions of efficient bactericidal activity against both MSSA and MRSA strains, blood glucose modulation, and control of active oxygen levels, has successfully promoted the healing of diabetic wounds in rats in 14 days. The hydrogel dressing exhibited significant effectiveness in facilitating the healing process of diabetic wounds, highlighting its considerable promise for clinical translation.