Influence of Gelatin Source and Bloom Number on Gelatin Methacryloyl Hydrogels Mechanical and Biological Properties for Muscle Regeneration

GelMA as scaffold material for epithelial cells to emulate the small intestinal microenvironment

Host-microbe interactions in the intestine play a significant role in health and disease. Novel scaffolds for host cells, capable of potentially supporting these intricate interactions, are necessary to improve our current systems for mimicking host-microbiota interplay in vitro/ex vivo. In this research paper, we study the application of gelatin methacrylamide (GelMA) as scaffold material for intestinal epithelial cells in terms of permeability, mechanical strength, and biocompatibility. We investigated whether the degree of substitution (DS) of GelMA influences the permeability and found that both high and low DS GelMA show sufficient permeability of biorelevant transport markers. Additionally, we researched epithelial cell adherence and viability, as well as mechanical characteristics of different concentrations of GelMA. All concentrations of hydrogel show long-term biocompatibility for the mono- and co-cultures, despite the goblet-like cells (LS174T) showing lower performance than enterocyte-like cells (Caco-2). The mechanical strength of all hydrogel concentrations was in a physiologically relevant range to be used as scaffold material for intestinal cells. Lastly, we examined the effect of the two sterilization methods, ethylene oxide (EO) and 70% ethanol followed by UVC (EtOH/UVC). We found that the impact of the two methods on the mechanical characteristics was minimal, and we did not find a significant effect between the two methods on cell viability and confluency of Caco-2 cells seeded on the GelMA hydrogels. Based on these results, we conclude that GelMA is a suitable material as a scaffold for intestinal cell types in terms of permeability, mechanical strength and biocompatibility. These findings contribute to the growing field of in vitro modeling of the gut and moves the field further to ensuring more translatable research on host-microbe interactions.

Combinational regenerative inductive effect of bio-adhesive hybrid hydrogels conjugated with hiPSC-derived myofibers and its derived EVs for volumetric muscle regeneration

In regenerative medicine, extracellular vesicles (EVs) possess the potential to repair injured cells by delivering modulatory factors. However, the therapeutic effect of EVs in large-scale tissue defects, which are subject to prolonged timelines for tissue architecture and functional restoration, remains poorly understood. In this study, we introduce EVs and cell-tethering hybrid hydrogels composed of tyramine-conjugated gelatin (GelTA) that can be in-situ crosslinked with EVs derived from human induced pluripotent stem cell-derived myofibers (hiPSC-myofibers) and hiPSC-muscle precursor cells. This hybrid hydrogel sustains the release of EVs and provides a beneficial nano-topography and mechanical properties for creating a favorable extracellular matrix. Secreted EVs from the hiPSC-myofibers contain specific microRNAs, potentially improving myogenesis and angiogenesis. Herein, we demonstrate increased myogenic markers and fusion/differentiation indexes through the combinatory effects of EVs and integrin-mediated adhesions in the 3D matrix. Furthermore, we observe a unique impact of EVs, which aid in maintaining the viability and phenotype of myofibers under harsh environments. The hybrid hydrogel in-situ crosslinked with hiPSCs and EVs is facilely used to fabricate large-scale muscle constructs by the stacking of micro-patterned hydrogel domains. Later, we confirmed a combinational effect, whereby muscle tissue regeneration and functional restoration were improved, via an in vivo murine volumetric muscle loss model.

Biological Functions of Macromolecular Protein Hydrogels in Constructing Osteogenic Microenvironment

Irreversible bone defects resulting from trauma, infection, and degenerative illnesses have emerged as a significant health concern. Structurally and functionally controllable hydrogels made by bone tissue engineering (BTE) have become promising biomaterials. Natural proteins are able to establish connections with autologous proteins through unique biologically active regions. Hydrogels based on proteins can simulate the bone microenvironment and regulate the biological behavior of stem cells in the tissue niche, making them candidates for research related to bone regeneration. This article reviews the biological functions of various natural macromolecular proteins (such as collagen, gelatin, fibrin, and silk fibroin) and highlights their special advantages as hydrogels. Then the latest research trends on cross-linking modified macromolecular protein hydrogels with improved mechanical properties and composite hydrogels loaded with exogenous micromolecular proteins have been discussed. Finally, the applications of protein hydrogels, such as 3D printed hydrogels, microspheres, and injectable hydrogels, were introduced, aiming to provide a reference for the repair of clinical bone defects.

Unveiling the versatility of gelatin methacryloyl hydrogels: a comprehensive journey into biomedical applications

Gelatin methacryloyl (GelMA) hydrogels have gained significant recognition as versatile biomaterials in the biomedical domain. GelMA hydrogels emulate vital characteristics of the innate extracellular matrix by integrating cell-adhering and matrix metalloproteinase-responsive peptide motifs. These features enable cellular proliferation and spreading within GelMA-based hydrogel scaffolds. Moreover, GelMA displays flexibility in processing, as it experiences crosslinking when exposed to light irradiation, supporting the development of hydrogels with adjustable mechanical characteristics. The drug delivery landscape has been reshaped by GelMA hydrogels, offering a favorable platform for the controlled and sustained release of therapeutic actives. The tunable physicochemical characteristics of GelMA enable precise modulation of the kinetics of drug release, ensuring optimal therapeutic effectiveness. In tissue engineering, GelMA hydrogels perform an essential role in the design of the scaffold, providing a biomimetic environment conducive to cell adhesion, proliferation, and differentiation. Incorporating GelMA in three-dimensional printing further improves its applicability in drug delivery and developing complicated tissue constructs with spatial precision. Wound healing applications showcase GelMA hydrogels as bioactive dressings, fostering a conducive microenvironment for tissue regeneration. The inherent biocompatibility and tunable mechanical characteristics of GelMA provide its efficiency in the closure of wounds and tissue repair. GelMA hydrogels stand at the forefront of biomedical innovation, offering a versatile platform for addressing diverse challenges in drug delivery, tissue engineering, and wound healing. This review provides a comprehensive overview, fostering an in-depth understanding of GelMA hydrogel's potential impact on progressing biomedical sciences.

GelMA synthesis and sources comparison for 3D multimaterial bioprinting

Gelatin Methacryloyl (GelMA) is one of the most used biomaterials for a wide range of applications, such as drug delivery, disease modeling and tissue regeneration. GelMA is obtained from gelatin, which can be derived from different sources (e.g., bovine skin, and porcine skin), through substitution of reactive amine and hydroxyl groups with methacrylic anhydride (MAA). The degree of functionalization (DoF) can be tuned by varying the MAA amount used; thus, different protocols, with different reaction efficiency, have been developed, using various alkaline buffers (e.g., phosphate-buffered saline, DPBS, or carbonate-bicarbonate solution). Obviously, DoF modulation has an impact on the final GelMA properties, so a deep investigation on the features of the obtained hydrogel must be carried on. The purpose of this study is to investigate how different gelatin sources and synthesis methods affect GelMA properties, as literature lacks direct and systematic comparisons between these parameters, especially between synthesis methods. The final aim is to facilitate the choice of the source or synthesis method according to the needs of the desired application. Hence, chemical and physical properties of GelMA formulations were assessed, determining the DoFs, mechanical and viscoelastic properties by rheological analysis, water absorption by swelling capacity and enzymatic degradation rates. Biological tests with lung adenocarcinoma cells (A549) were performed. Moreover, since 3D bioprinting is a rapidly evolving technology thanks to the possibility of precise deposition of cell-laden biomaterials (bioinks) to mimic the 3D structures of several tissues, the potential of different GelMA formulations as bioinks have been tested with a multi-material approach, revealing its printability and versatility in various applications.

Progress in cardiac tissue engineering and regeneration: Implications of gelatin-based hybrid scaffolds

Cardiovascular diseases, particularly myocardial infarction (MI), remain a leading cause of morbidity and mortality worldwide. Current treatments for MI, more palliative than curative, have limitations in reversing the disease completely. Tissue engineering (TE) has emerged as a promising strategy to address this challenge and may lead to improved therapeutic approaches for MI. Gelatin-based scaffolds, including gelatin and its derivative, gelatin methacrylate (GelMA), have attracted significant attention in cardiac tissue engineering (CTE) due to their optimal physical and biochemical properties and capacity to mimic the native extracellular matrix (ECM). CTE mainly recruits two classes of gelatin/GelMA-based scaffolds: hydrogels and nanofibrous. This article reviews state-of-the-art gelatin/GelMA-based hybrid scaffolds currently applied for CTE and regenerative therapy. Hybrid scaffolds, fabricated by combining gelatin/GelMA hydrogel or nanofibrous scaffolds with other materials such as natural/synthetic polymers, nanoparticles, protein-based biomaterials, etc., are explored for enhanced cardiac tissue regeneration functionality. The engraftment of stem/cardiac cells, bioactive molecules, or drugs into these hybrid systems shows great promise in cardiac tissue repair and regeneration. Finally, the role of gelatin/GelMA scaffolds combined with the 3D bioprinting strategy in CTE will also be briefly highlighted.

The Effect of Gelatin Source on the Synthesis of Gelatin-Methacryloyl and the Production of Hydrogel Microparticles

Gelatin methacryloyl (GelMA) is widely used for the formulation of hydrogels in diverse biotechnological applications. After the derivatization of raw gelatin, the degree of functionalization (DoF) is an attribute of particular interest as the functional residues are necessary for crosslinking. Despite progress in the optimization of the process found in the literature, a comparison of the effect of raw gelatin on the functionalization is challenging as various approaches are employed. In this work, the modification of gelatin was performed at room temperature (RT), and eight different gelatin products were employed. The DoF proved to be affected by the bloom strength and by the species of gelatin at an equal reactant ratio. Furthermore, batch-to-batch variability of the same gelatin source had an effect on the produced GelMA. Moreover, the elasticity of GelMA hydrogels depended on the DoF of the protein as well as on bloom strength and source of the raw material. Additionally, GelMA solutions were used for the microfluidic production of droplets and subsequent crosslinking to hydrogel. This process was developed as a single pipeline at RT using protein concentrations up to 20% (w/v). Droplet size was controlled by the ratio of the continuous to dispersed phase. The swelling behavior of hydrogel particles depended on the GelMA concentration.