Application of photo-crosslinkable gelatin methacryloyl in wound healing

Eumelanin pigment release from photo-crosslinkable methacrylated gelatin-based cryogels: Exploring the physicochemical properties and antioxidant efficacy in wound healing

Managing wounds in certain phases of the healing process still represents a big challenge. The oxidative stress, caused by reactive oxygen species (ROS), is one of the hallmarks controlling the wound healing-related process. Multifunctional biomaterials with excellent biocompatibility, tuneable properties, and easy functionalization, may allow realizing suitable three-dimensional (3D) and extracellular matrix (ECM)-mimicking structures, to efficiently control ROS levels. This might be a promising strategy for healing severe wounds. Herein, photo-crosslinkable methacrylated gelatin (GelMA)-based spongy-like cryogels (from 5 to 20 % w/v) incorporating Eumelanin from Black Soldier Flies (BSF-Eumel, 0.5 and 1.0 mg/mL), a pigment endowed with marked antioxidant properties, were developed. GelMA-based cryogels were fabricated by an easily handled and scalable cryogelation process followed by ultraviolet (UV) photo-crosslinking. BSF-Eumel sub-micrometer particles were embedded into GelMA-based cryogels by passive permeation of the solution within the polymeric network. BSF-Eumel addition resulted in more hydrophilic and porous structures, exhibiting a good stability and a prolonged release within 14 days. Furthermore, GelMA/BSF-Eumel cryogels exhibited good antioxidant activity, confirmed by a powerful quenching effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (59 % at 1.0 mg/mL of BSF-Eumel). Moreover, GelMA/BSF-Eumel cryogels at the highest GelMA concentrations (10 and 20 % w/v) accelerated human dermal fibroblasts-adult (HDF-a) migration, promoting wound closure within 24 h. They also proved to mitigate oxidative stress, modulating the production of ROS levels and preventing superoxide dismutase (SOD) activity inhibition in HDFs stimulated by lipopolysaccharide (LPS), owing to the release of BSF-Eumel. Such remarkable outcomes make GelMA/BSF-Eumel cryogels a promising antioxidant platform for wound healing.

In Situ-Formed Tissue-Adhesive Macroporous Scaffolds Enhance Cell Infiltration and Tissue Regeneration

Macroporous hydrogels have shown significant promise in tissue engineering and regenerative medicine. However, conventional macroporous scaffold fabrications are complex and incompatible with in situ customization and fabrication. Here, we propose a highly translational approach for the in situ formation of adhesive macroporous scaffolds through microfluidic homogenization of gas into a self-crosslinkable gelatin and transglutaminase (TG) mixture using a double syringe system. Using this strategy, the tissue defect can be evaluated, and the precursor, with the desired composition and volume, foamed and administered in situ. The TG-induced crosslinking stabilizes the pores, leading to strong tissue adhesion and accurate defect geometry approximation. We demonstrate precise control over the porosity, by changing the foaming parameters, and crosslinking kinetics, by adjusting the concentration of gelatin and TG. The resulting foam scaffolds offer controlled pore distribution, flexibility, tissue adhesion, stability, sustained protein release profile, and cell permissibility, with a faster biodegradation profile compared to bulk hydrogel compartments. Consequently, enhanced cell infiltration and reduced fibrous capsule formation are observed upon subcutaneous injection of foams compared to bulk hydrogels. Finally, the scaffolds demonstrate significant improvements in the rate and quality of the healing compared to the bulk hydrogels for the treatment of full-thickness cutaneous wounds in mice. STATEMENT OF SIGNIFICANCE: A highly translational method is presented for the in situ formation of tissue-adhesive macroporous scaffolds through microfluidic homogenization of gas into a self-crosslinkable hydrogel precursor using a double syringe system. This approach allows precise control over porosity and pore size, facilitating cell infiltration, tissue integration, and improved wound healing compared to bulk hydrogels, highlighting their potential in regenerative medicine.

Dual Delivery of Cells and Bioactive Molecules for Wound Healing Applications

Chronic wounds not only cause significant patient morbidity but also impose a substantial economic burden on the healthcare system. The primary barriers to wound healing include a deficiency of key modulatory factors needed to progress beyond the stalled inflammatory phase and an increased susceptibility to infections. While antimicrobial agents have traditionally been used to treat infections, stem cells have recently emerged as a promising therapy due to their regenerative properties, including the secretion of cytokines and immunomodulators that support wound healing. This study aims to develop an advanced dual-delivery system integrating stem cells and antibiotics. Stem cells have previously been delivered by encapsulation in gelatin methacrylate (GelMA) hydrogels. To explore a more effective delivery method, GelMA was processed into microparticles (MP). Compared to a bulk GelMA hydrogel (HG) encapsulation, GelMA MP supported greater cell growth and enhanced in vitro wound healing activity of human mesenchymal stem cells (hMSCs), likely due to a larger surface area for cell attachment and improved nutrient exchange. To incorporate antimicrobial properties, the broad-spectrum antibiotics penicillin/streptomycin (PS) were loaded into a bulk GelMA hydrogel, which was then cryo-milled into MPs to serve as carriers for hMSCs. To achieve a more sustained antibiotic release, gelatin nanoparticles (NP) were used as carriers for PS. PS was either incorporated during NP synthesis (NP+PS(S)) or absorbed into NP after synthesis (NP+PS(A)). MPs containing PS, NP+PS(S), or NP+PS(A) were tested for their cell carrier functions and antibacterial activities. The incorporation of PS did not compromise the cell-carrying function of MP configurations. The anti-S. aureus activity was detected in conditioned media from MPs for up to eight days-four days longer than from bulk HG containing PS. Notably, the presence of hMSCs prolonged the antimicrobial activity of MPs, suggesting a synergistic effect between stem cells and antibiotics. PS loaded via synthesis (NP+PS(S)) exhibited a delayed initial release, whereas PS loaded via absorption (NP+PS(A)) provided a more immediate release, with potential for sustained delivery. This study demonstrates the feasibility of a dual-delivery system integrating thera.

Dedifferentiated fat cells-derived exosomes (DFATs-Exos) loaded in GelMA accelerated diabetic wound healing through Wnt/β-catenin pathway

BACKGROUND

Diabetic foot ulcers pose significant challenges for clinicians worldwide. Cell-free exosome therapy holds great potential for wound healing. Dedifferentiated fat cells (DFATs) have been used in tissue engineering and regeneration, but there are no reports on the use of DFATs-derived exosomes in diabetic wound repair.

OBJECTIVES

This study aims to investigate whether DFATs-Exos accelerated diabetic wound healing and explore its potential mechanism.

METHODS

In vitro, DFATs-Exos were harvested from adipose tissue and used to treat endothelial cells (ECs) and fibroblasts. XAV939 was used as a Wnt/β-catenin pathway inhibitor. The biocompatibility of gelatin methacryloyl (GelMA) hydrogel was assessed. In vivo, DFAT-derived exosomes were encapsulated in 10% GelMA hydrogel and applied to a diabetic wound model. Histological analysis and wound closure rates were evaluated.

RESULTS

DFATs-Exos promoted angiogenesis in ECs and significantly alleviated the high glucose-induced inhibition of cell proliferation and migration by activating the Wnt/β-catenin pathway. In vivo, compared to DFAT-Exos or GelMA alone, the DFAT-Exos/GelMA combination accelerated wound closure and enhanced collagen maturity.

CONCLUSION

The DFAT-Exos/GelMA hydrogel significantly promoted wound healing in a diabetic animal model through activation of the Wnt/β-catenin signaling pathway.

Photo-Crosslinking Hydrogel Based on Porcine Small Intestinal Submucosa Decellularized Matrix/Fish Collagen/GelMA for Culturing Small Intestinal Organoids and Repairing Intestinal Defects

Organoid technology, as an innovative approach in biomedicine, exhibits promising prospects in disease modeling, pharmaceutical screening, regenerative medicine, and oncology research. However, the use of tumor-derived Matrigel as the primary method for culturing organoids has significantly impeded the clinical translation of organoid technology due to concerns about potential risks, batch-to-batch instability, and high costs. To address these challenges, this study innovatively introduced a photo-crosslinkable hydrogel made from a porcine small intestinal submucosa decellularized matrix (SIS), fish collagen (FC), and methacrylate gelatin (GelMA). The cost-effective hydrogel demonstrated excellent biocompatibility, tunable mechanical properties, rapid gelation properties, and low immunogenicity. Importantly, the proliferation and differentiation capacities of small intestinal organoids cultured in hydrogel were comparable to those in Matrigel, with no significant disparity observed. Furthermore, after one week of transplantation in nude mice, the hydrogel-organoid complex exhibited sustained structural and functional stability while preserving the differentiation characteristics of small intestinal organoids. Our study also demonstrated the effective potential of FC/SIS/GelMA hydrogel in accelerating the repair process of small intestinal defects, reducing the area of scar formation, and promoting the regeneration of both intestinal villi and smooth muscle tissue. In summary, this study presents a novel protocol for culturing small intestinal organoids, offering potential implications for future clinical applications and serving as an experimental foundation for the development of tissue-engineered intestines based on small intestinal organoids.

Lack of biochemical signalling in GelMA leads to polarity reversion in intestinal organoids independent from mechanoreciprocity

Xenogeneic tumour origin and batch-to-batch variability of Engelbreth-Holm-Swarm sarcoma tumour cell-derived hydrogels (Matrigel, Cultrex) limit the biomedical application of organoids in tissue engineering. The gelatin-methacryloyl (GelMA) hydrogels represent a defined, tunable, and GMP-friendly alternative, but they are rarely studied as alternative to Matrigel. Here, we studied effects of mechanical properties of GelMA and addition of laminin-111 on encapsulation and growth of small intestinal organoids. GelMA-embedded organoids displayed polarity reversion, resulting in apical-out and apical-basal phenotypes, independent from the matrix stiffness. Addition of laminin-111 softened hydrogels and also resulted in a partial restoration of the basal-out phenotype. Interestingly, despite the incomplete polarity restoration, GelMA-organoids still showed minor growth. GelMA stiffness and concentration influenced the transition from 3D to 2D organoid cultures. Collectively, our study confirms that tuning of GelMA mechanical properties alone cannot recapitulate the basal membrane matrix. However, controlled polarity reversion offers a tool for engineering organoids and enabling apical membrane access.

Progress in the Application of Hydrogels in Intervertebral Disc Repair: A Comprehensive Review

PURPOSE OF REVIEW

Intervertebral disc degeneration (IVDD) is a common orthopaedic disease and an important cause of lower back pain, which seriously affects the work and life of patients and causes a large economic burden to society. The traditional treatment of IVDD mainly involves early pain relief and late surgical intervention, but it cannot reverse the pathological course of IVDD. Current studies suggest that IVDD is related to the imbalance between the anabolic and catabolic functions of the extracellular matrix (ECM). Anti-inflammatory drugs, bioactive substances, and stem cells have all been shown to improve ECM, but traditional injection methods face short half-life and leakage problems.

RECENT FINDINGS

The good biocompatibility and slow-release function of polymer hydrogels are being noticed and explored to combine with drugs or bioactive substances to treat IVDD. This paper introduces the pathophysiological mechanism of IVDD, and discusses the advantages, disadvantages and development prospects of hydrogels for the treatment of IVDD, so as to provide guidance for future breakthroughs in the treatment of IVDD.

A tissue-adhesive, mechanically enhanced, natural Aloe Vera-based injectable hydrogel for wound healing: Macrophage mediation and collagen proliferation

Macromolecule hydrogels made from natural extracts have received much attention because of their favorable biocompatibility and wound healing properties. However, their clinical applications are limited by their insufficient mechanical strength and low adhesion properties. To overcome these limitations, we developed a novel injectable Aloe vera hydrogel (PDMA-GelMA@AV). By integrating gelatin methacrylate (GelMA) and polydopamine methacrylamide (PDMA), we significantly improved the mechanical and adhesion properties of the hydrogel. The PDMA-GelMA@AV hydrogel degraded in a simulated wound environment, which was synchronized with the sustained release of the bioactive components of A. vera. In vitro and in vivo analyses revealed that this hydrogel has good biocompatibility. In vitro studies also revealed that the sustained release of the active ingredients of A. vera promoted fibroblast proliferation and migration and increased the expression of key proteins and mRNAs required for wound healing. In addition, it modulated LPS-stimulated macrophages and decreased the expression of TNF-α, IL-1β and iNOS while increasing the expression of TGF-β and ARG. In vivo experiments further confirmed the efficacy of hydrogels in wound healing applications. These findings offer a novel perspective on the application of natural macromolecules as hydrogel-based delivery vehicles in wound care.

Recombinant human annexin A5 accelerates diabetic wounds healing by regulating skin inflammation

Background

One of the key obstacles to the healing of diabetic wound is the persistence of active inflammation. We previously demonstrated the potential of cell-free fat extract (CEFFE) to promote the healing of diabetic wounds, and annexin A5 (A5) is a crucial anti-inflammatory protein within CEFFE. This study aimed to evaluate the therapeutic potential of A5 in diabetic wounds.

Methods

A5 was loaded into GelMA hydrogels and applied to skin wounds of diabetic mice in vivo. The diabetic wounds with the treatment of GelMA-A5 were observed for 14 days and evaluated by histological analysis. Accessment of inflammation regulation were conducted through anti-CD68 staining, anti-CD86 and anti-CD206 staining, and qRT-PCR of wound tissue. In presence of A5, macrophages stimulated by lipopolysaccharide (LPS) in vitro, and detected through qRT-PCR, flow cytometry, and immunocytofluorescence staining. Besides, epithelial cells were co-cultured with A5 for epithelialization regulation by CCK-8 assay and cell migration assay.

Results

A5 could promote diabetic wound healing and regulate inflammations by promoting the transition of macrophages from M1 to M2 phenotype. In vitro experiments demonstrated that A5 exerted a significant effect on reducing pro-inflammatory factors and inhibiting the polarization of macrophages from M0 toward M1 phenotype. A5 significantly promoted the migration of epithelial cells.

Conclusion

Annexin A5 has a significant impact on the regulation of macrophage inflammation and promotion of epithelialization.

Development of nanocomposite hydrogel using citrate-containing amorphous calcium phosphate and gelatin methacrylate

Nanocomposite hydrogels are suitable in bone tissue engineering due to their resemblance with the extracellular matrix, ability to match complex geometries, and ability to provide a framework for cell attachment and proliferation. The nanocomposite hydrogel comprises organic and inorganic counterparts. Gelatin methacrylate (GELMA) is an extensively used organic biomaterial in tissue engineering due to its excellent biocompatibility, biodegradability, and bioactivity. The photo-crosslinking of GELMA presents a challenge when aiming to create thicker nanocomposite hydrogels due to opacity induced by fillers, which obstructs the penetration of ultraviolet (UV) light. Therefore, using a chemical crosslinking approach, we have developed nanocomposite GELMA hydrogel in this study by incorporating citrate-containing amorphous calcium phosphate (ACP_CIT). Ammonium persulfate (APS) and Tetramethylethylenediamine (TEMED) were deployed to crosslink the methacrylate group of GELMA. The oscillatory shear tests have confirmed that crosslinking enhances both storage (G') and loss modulus (G″) of GELMA. Subsequently, incorporation of ACP_CIT in GELMA hydrogel shows further enhancement in G' and G″ values. In vitro analysis of the developed hydrogels revealed that chemical crosslinking and incorporation of ACP_CIT do not compromise the cytocompatibility of the GELMA. Hence, for developing nanocomposite GELMA hydrogels employing APS/TEMED crosslinking emerges as a promising alternative to photo-crosslinking.

Development of a Sprayable Hydrogel-Based Wound Dressing: An In Vitro Model

Hydrogel-based dressings can effectively heal wounds by providing multiple functions, such as antibacterial, anti-inflammatory, and preangiogenic bioactivities. The ability to spray the dressing is important for the rapid and effective coverage of the wound surface. In this study, we developed a sprayable hydrogel-based wound dressing using naturally derived materials: hyaluronic acid and gelatin. We introduced methacrylate groups (HAMA and GelMA) to these materials to enable controllable photocrosslinking and form a stable hydrogel on the wound surface. To achieve sprayability, we evaluated the concentration of GelMA within a range of 5-15% (w/v) and then incorporated 1% (w/v) HAMA. Additionally, we incorporated calcium peroxide into the hydrogel at concentrations ranging from 0 to 12 mg/mL to provide self-oxygenation and antibacterial properties. The results showed that the composite hydrogels were sprayable and could provide oxygen for up to two weeks. The released oxygen relieved metabolic stress in fibroblasts and reduced cell death under hypoxia in in vitro culture. Furthermore, calcium peroxide added antibacterial properties to the wound dressing. In conclusion, the developed sprayable hydrogel dressing has the potential to be advantageous for wound healing due to its practical and conformable application, as well as its self-oxygenating and antibacterial functions.