Assessment of the characteristics and biocompatibility of gelatin sponge scaffolds prepared by various crosslinking methods

Biomedical application of materials for external auditory canal: History, challenges, and clinical prospects

Biomaterials play an integral role in treatment of external auditory canal (EAC) diseases. Regarding the special anatomic structure and physiological characteristics of EAC, careful selection of applicable biomaterials was essential step towards effective management of EAC conditions. The bioactive materials can provide reasonable biocompatibility, reduce risk of host pro-inflammatory response and immune rejection, and promote the healing process. In therapeutic procedure, biomaterials were employed for covering or packing the wound, protection of the damaged tissue, and maintaining of normal structures and functions of the EAC. Therefore, understanding and application of biomaterials was key to obtaining great rehabilitation in therapy of EAC diseases. In clinical practice, biomaterials were recognized as an important part in the treatment of different EAC diseases. The choice of biomaterials was distinct according to the requirements of various diseases. As a result, awareness of property regarding different biomaterials was fundamental for appropriate selection of therapeutic substances in different EAC diseases. In this review, we firstly introduced the characteristics of EAC structures and physiology, and EAC pathologies were summarized secondarily. From the viewpoint of biomaterials, the different materials applied to individual diseases were outlined in categories. Besides, the underlying future of therapeutic EAC biomaterials was discussed.

Humidity-Induced Protein-Based Artificial Synaptic Devices for Neuroprosthetic Applications

Neuroprosthetics and brain-machine interfaces are immensely beneficial for people with neurological disabilities, and the future generation of neural repair systems will utilize neuromorphic devices for the advantages of energy efficiency and real-time performance abilities. Conventional synaptic devices are not compatible to work in such conditions. The cerebrospinal fluid (CSF) in the central part of the nervous system is composed of 99% water. Therefore, artificial synaptic devices, which are the fundamental component of neuromorphic devices, should resemble biological nerves while being biocompatible, and functional in high-humidity environments with higher functional stability for real-time applications in the human body. In this work, artificial synaptic devices are fabricated based on gelatin-PEDOT: PSS composite as an active material to work more effectively in a highly humid environment (≈90% relative humidity). These devices successfully mimic various synaptic properties by the continuous variation of conductance, like, excitatory/inhibitory post-synaptic current(EPSC/IPSC), paired-pulse facilitation/depression(PPF/PPD), spike-voltage dependent plasticity (SVDP), spike-duration dependent plasticity (SDDP), and spike-rate dependent plasticity (SRDP) in environments at a relative humidity levels of ≈90%.

Complications of XEN gel stent implantation for the treatment of glaucoma: a systematic review

Aim

This study was aimed to summarize the complications and their management associated with XEN gel stent implantation.

Methods

A systematic review of literature was conducted using Medline (via PubMed), EMBASE, the Cochrane Library databases, and China National Knowledge Infrastructure, from their inception to February 1, 2024.

Results

A total of 48 studies published between 2017 and 2024 were identified and included in the systematic review, including 16 original studies (retrospective or prospective clinical studies), 28 case reports, and 4 case series, which followed patients for up to 5 years. Early postoperative complications of XEN gel stent implantation include hypotony maculopathy (1.9-4.6%), occlusion (3.9-8.8%), suprachoroidal hemorrhage (SCH), choroidal detachment (0-15%), conjunctival erosion, and exposure of the XEN gel stent (1.1-2.3%), wound and bleb leaks (2.1%) and malignant glaucoma (MG) (2.2%). Mid-postoperative complications of XEN gel stent implantation included migration of XEN (1.5%), ptosis (1.2%), endophthalmitis (0.4-3%), macular edema (1.5-4.3%), hypertrophic bleb (8.8%) and subconjunctival XEN gel stent fragmentation (reported in 2 cases). Late postoperative complications reported in cases included spontaneous dislocation and intraocular degradation.

Conclusion

XEN gel stent implantation is a minimally invasive glaucoma surgery (MIGS) procedure for glaucoma, known for its potential to minimize tissue damage and reduce surgical duration. However, it is crucial to note that despite these advantages, there remains a risk of severe complications, including endophthalmitis, SCH, and MG. Therefore, postoperative follow-up and early recognition of severe complications are essential for surgical management.

Fabrication and characterization of a multi-functional GBR membrane of gelatin-chitosan for osteogenesis and angiogenesis

Guided bone regeneration (GBR) membranes are widely used to treat bone defects. In this study, sequential electrospinning and electrospraying techniques were used to prepare a dual-layer GBR membrane composed of gelatin (Gel) and chitosan (CS) containing simvastatin (Sim)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres (Sim@PLGA/Gel-CS). As a GBR membrane, Sim@PLGA/Gel-CS could act as a barrier to prevent soft tissue from occupying regions of bone tissue. Furthermore, compared with traditional GBR membranes, Sim@PLGA/Gel-CS played an active role on stimulating osteogenesis and angiogenesis. Determination of the physical, chemical, and biological properties of Sim@PLGA/Gel-CS membranes revealed uniform sizes of the nanofibers and microspheres and appropriate morphologies. Fourier-transform infrared spectroscopy was used to characterize the interactions between Sim@PLGA/Gel-CS molecules and the increase in the number of amide groups in crosslinked membranes. The thermal stability and tensile strength of the membranes increased after N-(3-dimethylaminopropyl)-N9- ethylcarbodiimide/N-hydroxysuccinimide crosslinking. The increased fiber density of the barrier layer decreased fibroblast migration compared with that in the osteogenic layer. Osteogenic function was indicated by the increased alkaline phosphatase activity, calcium deposition, and neovascularization. In conclusion, the multifunctional effects of Sim@PLGA/Gel-CS on the barrier and bone microenvironment were achieved via its dual-layer structure and simvastatin coating. Sim@PLGA/Gel-CS has potential applications in bone tissue regeneration.

Lung-Mimetic Hydrofoam Sealant to Treat Pulmonary Air Leak

Pulmonary air leak is the most common complication of lung surgery, contributing to post-operative morbidity in up to 60% of patients; yet, there is no reliable treatment. Available surgical sealants do not match the demanding deformation mechanics of lung tissue; and therefore, fail to seal air leak. To address this therapeutic gap, a sealant with structural and mechanical similarity to subpleural lung is designed, developed, and systematically evaluated. This "lung-mimetic" sealant is a hydrofoam material that has alveolar-like porous ultrastructure, lung-like viscoelastic properties (adhesive, compressive, tensile), and lung extracellular matrix-derived signals (matrikines) to support tissue repair. In biocompatibility testing, the lung-mimetic sealant shows minimal cytotoxicity and immunogenicity in vitro. Human primary monocytes exposed to sealant matrikines in vitro upregulate key genes (MARCO, PDGFB, VEGF) known to correlate with pleural wound healing and tissue repair in vivo. In rat and swine models of pulmonary air leak, this lung-mimetic sealant rapidly seals air leak and restores baseline lung mechanics. Altogether, these data indicate that the lung-mimetic sealant can effectively seal pulmonary air leak and promote a favorable cellular response in vitro.

MicroRNA-200c Release from Gelatin-Coated 3D-Printed PCL Scaffolds Enhances Bone Regeneration

The fabrication of clinically relevant synthetic bone grafts relies on combining multiple biodegradable biomaterials to create a structure that supports the regeneration of defects while delivering osteogenic biomolecules that enhance regeneration. MicroRNA-200c (miR-200c) functions as a potent osteoinductive biomolecule to enhance osteogenic differentiation and bone formation; however, synthetic tissue-engineered bone grafts that sustain the delivery of miR-200c for bone regeneration have not yet been evaluated. In this study, we created novel, multimaterial, synthetic bone grafts from gelatin-coated 3D-printed polycaprolactone (PCL) scaffolds. We attempted to optimize the release of pDNA encoding miR-200c by varying gelatin types, concentrations, and polymer crosslinking materials to improve its functions for bone regeneration. We revealed that by modulating gelatin type, coating material concentration, and polymer crosslinking, we effectively altered the release rates of pDNA encoding miR-200c, which promoted osteogenic differentiation in vitro and bone regeneration in a critical-sized calvarial bone defect animal model. We also demonstrated that crosslinking the gelatin coatings on the PCL scaffolds with low-concentration glutaraldehyde was biocompatible and increased cell attachment. These results strongly indicate the potential use of gelatin-based systems for pDNA encoding microRNA delivery in gene therapy and further demonstrate the effectiveness of miR-200c for enhancing bone regeneration from synthetic bone grafts.

Strategies for Constructing Tissue-Engineered Fat for Soft Tissue Regeneration

BACKGROUND

Repairing soft tissue defects caused by inflammation, tumors, and trauma remains a major challenge for surgeons. Adipose tissue engineering (ATE) provides a promising way to solve this problem.

METHODS

This review summarizes the current ATE strategies for soft tissue reconstruction, and introduces potential construction methods for ATE.

RESULTS

Scaffold-based and scaffold-free strategies are the two main approaches in ATE. Although several of these methods have been effective clinically, both scaffold-based and scaffold-free strategies have limitations. The third strategy is a synergistic tissue engineering strategy and combines the advantages of scaffold-based and scaffold-free strategies.

CONCLUSION

Personalized construction, stable survival of reconstructed tissues and functional recovery of organs are future goals of building tissue-engineered fat for ATE.

Powdered Cross-Linked Gelatin Methacryloyl as an Injectable Hydrogel for Adipose Tissue Engineering

The tissue engineering field is currently advancing towards minimally invasive procedures to reconstruct soft tissue defects. In this regard, injectable hydrogels are viewed as excellent scaffold candidates to support and promote the growth of encapsulated cells. Cross-linked gelatin methacryloyl (GelMA) gels have received substantial attention due to their extracellular matrix-mimicking properties. In particular, GelMA microgels were recently identified as interesting scaffold materials since the pores in between the microgel particles allow good cell movement and nutrient diffusion. The current work reports on a novel microgel preparation procedure in which a bulk GelMA hydrogel is ground into powder particles. These particles can be easily transformed into a microgel by swelling them in a suitable solvent. The rheological properties of the microgel are independent of the particle size and remain stable at body temperature, with only a minor reversible reduction in elastic modulus correlated to the unfolding of physical cross-links at elevated temperatures. Salts reduce the elastic modulus of the microgel network due to a deswelling of the particles, in addition to triple helix denaturation. The microgels are suited for clinical use, as proven by their excellent cytocompatibility. The latter is confirmed by the superior proliferation of encapsulated adipose tissue-derived stem cells in the microgel compared to the bulk hydrogel. Moreover, microgels made from the smallest particles are easily injected through a 20G needle, allowing a minimally invasive delivery. Hence, the current work reveals that powdered cross-linked GelMA is an excellent candidate to serve as an injectable hydrogel for adipose tissue engineering.

Development and Application of an Advanced Biomedical Material-Silk Sericin

Sericin, a protein derived from silkworm cocoons, is considered a waste product derived from the silk industry for thousands of years due to a lack of understanding of its properties. However, in recent decades, a range of exciting properties of sericin are studied and uncovered, including cytocompatibility, low-immunogenicity, photo-luminescence, antioxidant properties, as well as cell-function regulating activities. These properties make sericin-based biomaterials promising candidates for biomedical applications. This review summarizes the properties and bioactivities of silk sericin and highlights the latest developments in sericin in tissue engineering and regenerative medicine. Furthermore, the extended application of sericin in developing flexible electronic devices and 3D bioprinting is also discussed. It is believed that sericin-based biomaterials have great potential of being developed into novel tissue engineering products and smart implantable devices for various medical applications toward improving clinical outcomes.

Progress in injectable hydrogels for the treatment of incompressible bleeding: an update

Uncontrollable haemorrhage from deep, noncompressible wounds remains a persistent and intractable challenge, accounting for a very high proportion of deaths in both war and disaster situations. Recently, injectable hydrogels have been increasingly studied as potential haemostatic materials, highlighting their enormous potential for the management of noncompressible haemorrhages. In this review, we summarize haemostatic mechanisms, commonly used clinical haemostatic methods, and the research progress on injectable haemostatic hydrogels. We emphasize the current status of injectable hydrogels as haemostatic materials, including their physical and chemical properties, design strategy, haemostatic mechanisms, and application in various types of wounds. We discuss the advantages and disadvantages of injectable hydrogels as haemostatic materials, as well as the opportunities and challenges involved. Finally, we propose cutting-edge research avenues to address these challenges and opportunities, including the combination of injectable hydrogels with advanced materials and innovative strategies to increase their biocompatibility and tune their degradation profile. Surface modifications for promoting cell adhesion and proliferation, as well as the delivery of growth factors or other biologics for optimal wound healing, are also suggested. We believe that this paper will inform researchers about the current status of the use of injectable haemostatic hydrogels for noncompressible haemorrhage and spark new ideas for those striving to propel this field forward.

Advancements in gelatin-based hydrogel systems for biomedical applications: A state-of-the-art review

A gelatin-based hydrogel system is a stimulus-responsive, biocompatible, and biodegradable polymeric system with solid-like rheology that entangles moisture in its porous network that gradually protrudes to assemble a hierarchical crosslinked arrangement. The hydrolysis of collagen directs gelatin construction, which retains arginyl glycyl aspartic acid and matrix metalloproteinase-sensitive degeneration sites, further confining access to chemicals entangled within the gel (e.g., cell encapsulation), modulating the release of encapsulated payloads and providing mechanical signals to the adjoining cells. The utilization of various types of functional tunable biopolymers as scaffold materials in hydrogels has become highly attractive due to their higher porosity and mechanical ability; thus, higher loading of proteins, peptides, therapeutic molecules, etc., can be further modulated. Furthermore, a stimulus-mediated gelatin-based hydrogel with an impaired concentration of gellan demonstrated great shear thinning and self-recovering characteristics in biomedical and tissue engineering applications. Therefore, this contemporary review presents a concise version of the gelatin-based hydrogel as a conceivable biomaterial for various biomedical applications. In addition, the article has recapped the multiple sources of gelatin and their structural characteristics concerning stimulating hydrogel development and delivery approaches of therapeutic molecules (e.g., proteins, peptides, genes, drugs, etc.), existing challenges, and overcoming designs, particularly from drug delivery perspectives.

Superporous soy protein isolate matrices as superabsorbent dressings for successful management of highly exuding wounds: In vitro and in vivo characterization

Soy protein isolate (SPI) has received widespread attention of the biomedical research community primarily due to its good biocompatibility, biodegradability, high availability and low cost. Herein, glutaraldehyde cross-linked microporous sponge-like SPI scaffolds were prepared using the cryogelation technique for tissue engineering applications. The prepared SPI scaffolds possess an interconnected porous structure with approximately 90% porosity and an average pore size in the range of 45-92 μm. The morphology, porosity, swelling capacity and degradation rate of the cryogels were found to be dependent on the concentration of polymer to crosslinking agent. All cryogels were found to be elastic and able to maintain physical integrity even after being compressed to one-fifth of their original length during cyclic compression analysis. These cryogels showed excellent mechanical properties, immediate water-triggered shape restoration and absorption speed. Furthermore, cryogels outperformed cotton and gauze in terms of blood clotting and blood cell adherence. The in vitro and in vivo studies demonstrated the potency of SPI scaffolds for skin tissue engineering applications. Our findings showed that crosslinking with glutaraldehyde had no detrimental effects on cell viability. In addition, an in vivo wound healing study in rats validated them as good potential wound dressing materials.

Crosslinked modified decellularized rabbit conjunctival stroma for reconstruction of tissue-engineered conjunctivain vitro

Conjunctival reconstruction is an essential part of ocular surface restoration, especially in severe conjunctival disorders. Decellularized conjunctival tissues have been used in tissue engineering. In this study, we investigated the feasibility of constructing tissue-engineered conjunctiva using stem cell (human amniotic epithelial cells, hAECs), and cross-linked modified decellularized rabbit conjunctival stroma (DRCS-Asp-hEGF), and decellularized rabbit conjunctiva stroma (DRCS). With phospholipase A2 and sodium dodecyl, DRCS were nearly DNA-free, structurally intact and showed no cytotoxic effectsin vitro, as confirmed by DNA quantification, histology, and immunofluorescence. The results of Fourier transform infrared, Alcian blue staining and human epidermal growth factor (hEGF) release assays showed that DRCS-Asp-hEGF was successfully prepared via crosslinking with aspartic acid (Asp) and modified by hEGF at pH 7.7. The hAECs were positive for octamer-binding transcription factor-4 and ABCG2 cell markers. The hAECs were directly placed on the DRCS and DRCS-Asp-hEGF for five days respectively. Tissue-engineered conjunctiva was constructedin vitrofor five days, and the fluorescence staining results showed that hAECs grew in monolayers on DRCS-Asp-hEGF and DRCS. Flow cytometry results showed that compared with DRCS, the number of apoptotic cells stained in DRCS-Asp-hEGF was small, 86.70 ± 0.79% of the cells survived, and 87.59 ± 1.43% of the cells were in the G1 phase of DNA synthesis. Electron microscopy results showed that desmosome junction structures, which were similar to the native conjunctival tissue, were formed between cells and the matrix in the DRCS-Asp-hEGF.

Gelatin scaffold ameliorates proliferation & stem cell differentiation into the hepatic like cell and support liver regeneration in partial-hepatectomized mice model

Stem cell-based tissue engineering is an emerging tool for developing functional tissues of choice. To understand pluripotency and hepatic differentiation of mouse embryonic stem cells (mESCs) on a three-dimensional (3D) scaffold, we established an efficient approach for generating hepatocyte-like cells (HLCs) from hepatoblast cells. We developed porous and biodegradable scaffold, which was stimulated with exogenous growth factors and investigated stemness and differentiation capacity of mESCs into HLCs on the scaffoldin-vitro. In animal studies, we had cultured mESCs-derived hepatoblast-like cells on the scaffold and then, transplanted them into the partially hepatectomized C57BL/6 male mice model to evaluate the effect of gelatin scaffold on hepatic regeneration. The 3D culture system allowed maintenance of stemness properties in mESCs. The step-wise induction of mESCs with differentiation factors leads to the formation of HLCs and expressed liver-specific genes, including albumin, hepatocyte nucleic factor 4 alpha, and cytokeratin 18. In addition, cells also expressed Ki67, indicating cells are proliferating. The secretome showed expression of albumin, urea, creatinine, alanine transaminase, and aspartate aminotransferase. However, the volume of the excised liver which aids regeneration has not been studied. Our results indicate that hepatoblast cells on the scaffold implanted in PH mouse indicates that these cells efficiently differentiate into HLCs and cholangiocytes, forming hepatic lobules with central and portal veins, and bile duct-like structures with neovascularization. The gelatin scaffold provides an efficient microenvironment for liver differentiation and regeneration bothin-vitroandin-vivo. These hepatoblasts cells would be a valuable source for 3D liver tissue engineering/transplantation in liver diseases.

Electrospinning Microencapsulation of Lactobacillus fermentum K73 Using Gelatin as the Main Component of a Food-Grade Matrix

This work aimed to establish the conditions that improve the viability of Lactobacillus fermentum K73 during and after the electrospinning process. A mixture of experimental designs were performed to select the formulation (gelatin and bacterial culture) that improves the probiotic viability after blending and under simulated gastrointestinal conditions. A Box-Behnken design was performed to improve the encapsulation yield and survival during the electrospinning process. For the Box-Behnken design, the factors were soy lecithin and bacteria culture concentration at the blend and collector distance for electrospinning. It was hypothesized that soy lecithin improved the electrospinnability, acting as a surfactant in the mixture and allowing lower voltage to be used during the process. The selected volume ratio of the gelatin (25%)/bacterial culture mixture was 0.66/0.34. The physicochemical parameters of the selected blend were in the recommended range for electrospinning. The conditions that improved the encapsulation yield and survival during electrospinning were 200 g/L of bacterial culture, 2.5% (w/v) soy lecithin, and 7 cm collector distance. The experimental encapsulation yield and survival was 80.7%, with an experimental error of 7.2%. SEM micrographs showed the formation of fibers with gelatin/bacterial culture beads. Encapsulation improved the viability of the probiotic under simulated gastrointestinal conditions compared to free cells.

Crosslinking strategies in modulating methylcellulose hydrogel properties

Methylcellulose (MC) hydrogels are ideal materials for the design of thermo-responsive platforms capable of exploiting the environment temperature as a driving force to activate their smart transition. However, MC hydrogels usually show reduced stability in an aqueous environment and low mechanical properties, limiting their applications' breadth. A possible approach intended to overcome these limitations is chemical crosslinking, which represents a simple yet effective strategy to modify the MC hydrogels' properties (e.g., physicochemical, mechanical, and biological). In this regard, understanding the selected crosslinking method's role in modulating the MC hydrogels' properties is a key factor in their design. This review offers a perspective on the main MC chemical crosslinking approaches reported in the literature. Three main categories can be distinguished: (i) small molecule crosslinkers, (ii) crosslinking by high-energy radiation, and (iii) crosslinking via MC chemical modification. The advantages and limitations of each approach are elucidated, and special consideration is paid to the thermo-responsive properties after crosslinking towards the development of MC hydrogels with enhanced physical stability and mechanical performance, preserving the thermo-responsive behavior.

Bioactive Polyetheretherketone with Gelatin Hydrogel Leads to Sustained Release of Bone Morphogenetic Protein-2 and Promotes Osteogenic Differentiation

Polyetheretherketone (PEEK) is one of the most promising implant materials for hard tissues due to its similar elastic modulus; however, usage of PEEK is still limited owing to its biological inertness and low osteoconductivity. The objective of the study was to provide PEEK with the ability to sustain the release of growth factors and the osteogenic differentiation of stem cells. The PEEK surface was sandblasted and modified with polydopamine (PDA). Moreover, successful sandblasting and PDA modification of the PEEK surface was confirmed through physicochemical characterization. The gelatin hydrogel was then chemically bound to the PEEK by adding a solution of glutaraldehyde and gelatin to the surface of the PDA-modified PEEK. The binding and degradation of the gelatin hydrogel with PEEK (GPEEK) were confirmed, and the GPEEK mineralization was observed in simulated body fluid. Sustained release of bone morphogenetic protein (BMP)-2 was observed in GPEEK. When cultured on GPEEK with BMP-2, human mesenchymal stem cells (hMSCs) exhibited osteogenic differentiation. We conclude that PEEK with a gelatin hydrogel incorporating BMP-2 is a promising substrate for bone tissue engineering.

Novel Hydrophilic Oligomer-Crosslinked Gelatin-Based Hydrogels for Biomedical Applications

Gelatin-based hydrogels have shown good injectability and biocompatibility and have been broadly used for drug delivery and tissue regeneration. However, their low mechanical strengths and fast degradation rates must be modified for long-term implantation applications. With an aim to develop mechanically stable hydrogels, reactive anhydride-based oligomers were developed and used to fabricate gelatin-based crosslinked hydrogels in this study. A cascade of hydrophilic oligomers containing reactive anhydride groups was synthesized by free radical polymerization. These oligomers varied in degree of reactivity, comonomer composition, and showed low molecular weights (M_n < 5 kDa). The reactive oligomers were utilized to fabricate hydrogels that differed in their mechanical strengths and degradation profiles. These formulations exhibited good cytocompatibility with human adipose tissue-derived stem cells (hADCs). In conclusion, the reactive MA-containing oligomers were successfully synthesized and utilized for the development of oligomer-crosslinked hydrogels. Such oligomer-crosslinked gelatin-based hydrogels hold promise as drug or cell carriers in various biomedical applications.

Concentration Selection of Biofriendly Enzyme-Modified Gelatin Hydrogels for Periodontal Bone Regeneration

Periodontitis is challenging to cure radically due to its complex periodontal structure and particular microenvironment of dysbiosis and inflammation. However, with the assistance of various materials, cell osteogenic differentiation could be improved, and the ability of hard tissue regeneration could be enhanced. This study aimed to explore the appropriate concentration ratio of biofriendly transglutaminase-modified gelatin hydrogels for promoting periodontal alveolar bone regeneration. Through a series of characterization and cell experiments, we found that all the hydrogels possessed multi-space network structures and demonstrated their biocompatibility. In vivo and in vitro osteogenic differentiation experiments also confirmed that the group 40-5 (transglutaminase-gelatin concentration ratio) possessed a favorable osteogenic potential. In summary, we conclude that such hydrogel with a 40-5 concentration is most conducive to promoting periodontal bone reconstruction, which might be a new route to deal with the dilemma of clinical periodontal treatment.

The Utilisation of Hydrogels for iPSC-Cardiomyocyte Research

Cardiac fibroblasts' (FBs) and cardiomyocytes' (CMs) behaviour and morphology are influenced by their environment such as remodelling of the myocardium, thus highlighting the importance of biomaterial substrates in cell culture. Biomaterials have emerged as important tools for the development of physiological models, due to the range of adaptable properties of these materials, such as degradability and biocompatibility. Biomaterial hydrogels can act as alternative substrates for cellular studies, which have been particularly key to the progression of the cardiovascular field. This review will focus on the role of hydrogels in cardiac research, specifically the use of natural and synthetic biomaterials such as hyaluronic acid, polydimethylsiloxane and polyethylene glycol for culturing induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). The ability to fine-tune mechanical properties such as stiffness and the versatility of biomaterials is assessed, alongside applications of hydrogels with iPSC-CMs. Natural hydrogels often display higher biocompatibility with iPSC-CMs but often degrade quicker, whereas synthetic hydrogels can be modified to facilitate cell attachment and decrease degradation rates. iPSC-CM structure and electrophysiology can be assessed on natural and synthetic hydrogels, often resolving issues such as immaturity of iPSC-CMs. Biomaterial hydrogels can thus provide a more physiological model of the cardiac extracellular matrix compared to traditional 2D models, with the cardiac field expansively utilising hydrogels to recapitulate disease conditions such as stiffness, encourage alignment of iPSC-CMs and facilitate further model development such as engineered heart tissues (EHTs).

Application of polyvinyl alcohol/chitosan copolymer hydrogels in biomedicine: A review

Hydrogels is a hydrophilic, cross-linked polymer of three-dimensional network structures. The application of hydrogels prepared from a single polymer in the biomedical field has many drawbacks. The functional blend of polyvinyl alcohol and chitosan allows hydrogels to have better and more desirable properties than those produced from a single polymer, which is a good biomaterial for development and design. In this paper, we have reviewed the progress in the application of polyvinyl alcohol/chitosan composite hydrogels in various medical fields, the different cross-linking agents and cross-linking methods, and the research progress in the optimization of composite hydrogels for their subsequent wide range of biomedical applications.

Bioconjugation of Carbohydrates to Gelatin Sponges Promoting 3D Cell Cultures

Gelatin sponges are widely employed as hemostatic agents, and are gaining increasing interest as 3D scaffolds for tissue engineering. To broaden their possible application in the field of tissue engineering, a straightforward synthetic protocol able to anchor the disaccharides, maltose and lactose, for specific cell interactions was developed. A high conjugation yield was confirmed by ¹H-NMR and FT-IR spectroscopy, and the morphology of the resulting decorated sponges was characterized by SEM. After the crosslinking reaction, the sponges preserve their porous structure as ascertained by SEM. Finally, HepG2 cells cultured on the decorated gelatin sponges show high viability and significant differences in the cellular morphology as a function of the conjugated disaccharide. More spherical morphologies are observed when cultured on maltose-conjugated gelatin sponges, while a more flattened aspect is discerned when cultured onto lactose-conjugated gelatin sponges. Considering the increasing interest in small-sized carbohydrates as signaling cues on biomaterial surfaces, systematic studies on how small carbohydrates might influence cell adhesion and differentiation processes could take advantage of the described protocol.

3D Bioprintable Hypoxia-Mimicking PEG-Based Nano Bioink for Cartilage Tissue Engineering

As hypoxia plays a significant role in the formation and maintenance of cartilage tissue, aiming to develop native hypoxia-mimicking tissue engineering scaffolds is an efficient method to treat articular cartilage (AC) defects. Cobalt (Co) is documented for its hypoxic-inducing effects in vitro by stabilizing the hypoxia-inducible factor-1α (HIF-1α), a chief regulator of stem cell fate. Considering this, we developed a novel three-dimensional (3D) bioprintable hypoxia-mimicking nano bioink wherein cobalt nanowires (Co NWs) were incorporated into the poly(ethylene glycol) diacrylate (PEGDA) hydrogel system as a hypoxia-inducing agent and encapsulated with umbilical cord-derived mesenchymal stem cells (UMSCs). In the current study, we investigated the impact of Co NWs on the chondrogenic differentiation of UMSCs in the PEGDA hydrogel system. Herein, the hypoxia-mimicking nano bioink (PEGDA+Co NW) was rheologically optimized to bioprint geometrically stable cartilaginous constructs. The bioprinted 3D constructs were evaluated for their physicochemical characterization, swelling-degradation behavior, mechanical properties, cell proliferation, and the expression of chondrogenic markers by histological, immunofluorescence, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) methods. The results disclosed that, compared to the control (PEGDA) group, the hypoxia-mimicking nano bioink (PEGDA+Co NW) group outperformed in print fidelity and mechanical properties. Furthermore, live/dead staining, double-stranded DNA (dsDNA) content, and glycosaminoglycans (GAGs) content demonstrated that adding low amounts of Co NWs (<20 ppm) into PEGDA hydrogel system supported UMSC adhesion, proliferation, and differentiation. Histological and immunofluorescence staining of the PEGDA+Co NW bioprinted structures revealed the production of type 2 collagen (COL2) and sulfated GAGs, rendering it a feasible option for cartilage repair. It was further corroborated by a significant upregulation of the hypoxia-mediated chondrogenic and downregulation of the hypertrophic/osteogenic marker expression. In conclusion, the hypoxia-mimicking hydrogel system, including PEGDA and Co²⁺ ions, synergistically directs the UMSCs toward the chondrocyte lineage without using expensive growth factors and provides an alternative strategy for translational applications in the cartilage tissue engineering field.

Effect of mold shape on the microstructure of gelatin sponges for tissue engineering applications

Gelatin sponges have been used in several medical applications including tissue replacement, scaffolds, and hemostasis. Each application requires specific parameters that are tuned by the porosity of the sponges. Therefore, changes in the porosity profile of the sponges would change the sponge behavior. In this study, a gelatin solution was prepared and crosslinked with glutaraldehyde. Afterward, the solution was poured into three different mold structures with different volumes and frozen at a constant freezing rate. Each mold was investigated for its physical characteristics including swelling, degradation, porosity, crystallinity, and mechanical compression. Cube-molded gelatin sponges demonstrated high swelling capacity, degradation rate, and porosity while exhibiting low crystallinity, yield strength, and elasticity. These characteristics are suitable for hemostatic application and tissue regeneration. Therefore, it is recommended to freeze dry gelatin sponge in cuboid-shaped dimensions, for research or industry, to control the porosity and crystallinity of the sponge for the best result in biomedical applications.

Could Local Application of Hypoxia Inducible Factor 1-α Enhancer Deferoxamine Be Promising for Preventing of Medication-Related Osteonecrosis of the Jaw?

This experimental study investigates the prophylactic effect of deferoxamine (DFO) on medication-related osteonecrosis of the jaw (MRONJ). Thirty-six female Sprague Dawley rats received zoledronic acid (ZA) for eight weeks to create an osteonecrosis model. DFO was locally applied into the extraction sockets with gelatin sponge (GS) carriers to prevent MRONJ. The specimens were histopathologically and histomorphometrically evaluated. Hypoxia-inducible factor 1-alpha (HIF-1α) protein levels in the extraction sockets were quantified. New bone formation rate differed significantly between groups (p = 0.005). Newly formed bone ratios in the extraction sockets did not differ significantly between the control group and the GS (p = 1), GS/DFO (p = 0.749), ZA (p = 0.105), ZA-GS (p = 0.474), and ZA-GS/DFO (p = 1) groups. While newly formed bone rates were higher in the ZA-GS and ZA-GS/DFO groups than in the ZA group, the differences were not significant. HIF-1α levels differed significantly between groups (p < 0.001) and were significantly higher in the DFO and ZA-GS/DFO groups than in the control group (p = 0.001 and p = 0.004, respectively). While HIF-1α levels were higher in the ZA-GS/DFO group than in the ZA group, the difference was not significant. While HIF-1α protein levels and new bone formation rate were elevated in the DFO-treated group, the effect was not significant. Further large-scale studies are needed to understand DFO’s preventative effects on MRONJ and the role of HIF-1α in MRONJ pathogenesis.

An Antibacterial and Antiadhesion In Situ Forming Hydrogel with Sol-Spray System for Noncompressible Hemostasis

Noncompressible hemorrhage is a major cause of posttrauma death and occupies the leading position among potentially preventable trauma-associated deaths. Recently, multiple studies have shown that strongly adhesive materials can serve as hemostatic materials for noncompressible hemorrhage. However, the risk of severe tissue adhesion limits the use of adhesive hydrogels as hemostatic materials. Here, we report a promising material system comprising an injectable sol and liquid spray as a potential solution. Injectable sol is mainly composed of gelatin (GEL) and sodium alginate (SA), which possess hemostasis and adhesive properties. The liquid spray component, a mixture of tannic acid (TA) and calcium chloride (CaCl₂), rapidly forms an antibacterial, antiadhesive and smooth film structure upon contact with the sol. In vitro and in vivo experiments demonstrated the bioabsorbable, biocompatible, antibacterial, and antiadhesion properties of the in situ forming hydrogel with a sol-spray system. Importantly, the addition of tranexamic acid (TXA) enhanced hemostatic performance in noncompressible areas and in deep wound hemorrhage. Our study offers a new multifunctional hydrogel system to achieve noncompressible hemostasis.

Development of Gelatin-Coated Hydrogel Microspheres for Novel Bioink Design: A Crosslinker Study

The development of vascularized tissue is a substantial challenge within the field of tissue engineering and regenerative medicine. Studies have shown that positively-charged microspheres exhibit dual-functions: (1) facilitation of vascularization and (2) controlled release of bioactive compounds. In this study, gelatin-coated microspheres were produced and processed with either EDC or transglutaminase, two crosslinkers. The results indicated that the processing stages did not significantly impact the size of the microspheres. EDC and transglutaminase had different effects on surface morphology and microsphere stability in a simulated colonic environment. Incorporation of EGM and TGM into bioink did not negatively impact bioprintability (as indicated by density and kinematic viscosity), and the microspheres had a uniform distribution within the scaffold. These microspheres show great potential for tissue engineering applications.

Semi-Synthetic Click-Gelatin Hydrogels as Tunable Platforms for 3D Cancer Cell Culture

Basement membrane extracts (BME) derived from Engelbreth-Holm-Swarm (EHS) mouse sarcomas such as Matrigel^® remain the gold standard extracellular matrix (ECM) for three-dimensional (3D) cell culture in cancer research. Yet, BMEs suffer from substantial batch-to-batch variation, ill-defined composition, and lack the ability for physichochemical manipulation. Here, we developed a novel 3D cell culture system based on thiolated gelatin (Gel-SH), an inexpensive and highly controlled raw material capable of forming hydrogels with a high level of biophysical control and cell-instructive bioactivity. We demonstrate the successful thiolation of gelatin raw materials to enable rapid covalent crosslinking upon mixing with a synthetic poly(ethylene glycol) (PEG)-based crosslinker. The mechanical properties of the resulting gelatin-based hydrogels were readily tuned by varying precursor material concentrations, with Young's moduli ranging from ~2.5 to 5.8 kPa. All hydrogels of varying stiffnesses supported the viability and proliferation of MDA-MB-231 and MCF-7 breast cancer cell lines for 14 and 21 days of cell culture, respectively. Additionally, the gelatin-based hydrogels supported the growth, viability, and osteogenic differentiation of patient-derived preosteoblasts over 28 days of culture. Collectively, our data demonstrate that gelatin-based biomaterials provide an inexpensive and tunable 3D cell culture platform that may overcome the limitations of traditional BMEs.

Enzymatic Crosslinked Hydrogels of Gelatin and Poly (Vinyl Alcohol) Loaded with Probiotic Bacteria as Oral Delivery System

Probiotic bacteria are widely used to prepare pharmaceutical products and functional foods because they promote and sustain health. Nonetheless, probiotic viability is prone to decrease under gastrointestinal conditions. In this investigation, Lactiplantibacillus plantarum spp. CM-CNRG TB98 was entrapped in a gelatin−poly (vinyl alcohol) (Gel−PVA) hydrogel which was prepared by a “green” route using microbial transglutaminase (mTGase), which acts as a crosslinking agent. The hydrogel was fully characterized and its ability to entrap and protect L. plantarum from the lyophilization process and under simulated gastric and intestine conditions was explored. The Gel−PVA hydrogel showed a high probiotic loading efficiency (>90%) and survivability from the lyophilization process (91%) of the total bacteria entrapped. Under gastric conditions, no disintegration of the hydrogel was observed, keeping L. plantarum protected with a survival rate of >94%. While in the intestinal fluid the hydrogel is completely dissolved, helping to release probiotics. A Gel−PVA hydrogel is suitable for a probiotic oral administration system due to its physicochemical properties, lack of cytotoxicity, and the protection it offers L. plantarum under gastric conditions.

Barrier Membranes for Guided Bone Regeneration (GBR): A Focus on Recent Advances in Collagen Membranes

Guided bone regeneration (GBR) has become a clinically standard modality for the treatment of localized jawbone defects. Barrier membranes play an important role in this process by preventing soft tissue invasion outgoing from the mucosa and creating an underlying space to support bone growth. Different membrane types provide different biological mechanisms due to their different origins, preparation methods and structures. Among them, collagen membranes have attracted great interest due to their excellent biological properties and desired bone regeneration results to non-absorbable membranes even without a second surgery for removal. This work provides a comparative summary of common barrier membranes used in GBR, focusing on recent advances in collagen membranes and their biological mechanisms. In conclusion, the review article highlights the biological and regenerative properties of currently available barrier membranes with a particular focus on bioresorbable collagen-based materials. In addition, the advantages and disadvantages of these biomaterials are highlighted, and possible improvements for future material developments are summarized.

A Simple Preparation Method of Gelatin Hydrogels Incorporating Cisplatin for Sustained Release

The objective of this study was to develop a new preparation method for cisplatin (CDDP)-incorporated gelatin hydrogels without using chemical crosslinking nor a vacuum heating instrument for dehydrothermal crosslinking. By simply mixing CDDP and gelatin, CDDP-crosslinked gelatin hydrogels (CCGH) were prepared. CDDP functions as a crosslinking agent of gelatin to form the gelatin hydrogel. Simultaneously, CDDP is incorporated into the gelatin hydrogel as a controlled release carrier. CDDP's in vitro and in vivo anticancer efficacy after incorporation into CCGH was evaluated. In the in vitro system, the CDDP was released gradually due to CCGH degradation with an initial burst release of approximately 16%. CDDP metal-coordinated with the degraded fragment of gelatin was released from CCGH with maintaining the anticancer activity. After intraperitoneal administration of CCGH, CDDP was detected in the blood circulation while its toxicity was low. Following intraperitoneal administration of CCGH in a murine peritoneal dissemination model of human gastric cancer MKN45-Luc cell line, the survival time was significantly prolonged compared with free CDDP solution. It is concluded that CCGH prepared by the CDDP-based crosslinking of gelatin is an excellent sustained release system of CDDP to achieve superior anticancer effects with minimal side effects compared with free CDDP solution.

A biomimetic double network hydrogel ameliorates renal fibrosis and promotes renal regeneration

Acute kidney injury (AKI) and chronic kidney disease (CKD) are serious global public health issues. Both interconnect closely, and AKI-CKD transition significantly increases the morbidity of CKD and inevitably progresses to end stage renal disease. However, with the current drug delivery system it is hard to achieve precise delivery and apply it to clinical practice due to the local fibrotic milieu of the AKI-CKD transition procedure. Consequently, new treatment options to halt or even reverse AKI-CKD transition are urgently needed. Curcumin and Ac-SDKP were proved to be capable of ameliorating renal injury and restoring renal biological function. However, due to the water-insolubility, poor absorption and ease of degradation features, their utilization based on traditional drug delivery systems was still confined to the laboratory. A new approach for the targeted delivery of curcumin and Ac-SDKP into kidneys is needed. Hydrogels, owing to their capability of targeted-drug delivery and bio-favorable nature, emerge as a promising resolution. Herein, we developed a bioinspired double network hydrogel scaffold loaded with curcumin and N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) to explore the feasibility of drug-loaded hydrogels for treatment of AKI-CKD transition. This double network hydrogel (GCS) was prepared based on gelatin and curcumin-zinc with polydopamine (DOPA) coating and then immobilized with Ac-SDKP on the surface. The prepared hydrogels possessed appropriate porosity, suitable mechanical properties, and excellent biocompatibility. In vitro, the GCS hydrogel was demonstrated to be pro-angiogenic, anti-oxidative and anti-fibrotic. In vivo, after the GCS hydrogel was implanted into partially nephrectomized rat kidneys, local renal fibrosis was observed to be improved significantly, and neo-blood vessels and neonatal renal tubules appeared around the implanted area. We speculated that the GCS hydrogel could ameliorate renal fibrosis and injury significantly and stimulate regeneration in situ. Taken together, this study demonstrated the promising potential of this bioinspired hydrogel scaffold for renal injury repair and renal regeneration.

Cryostructuring of Polymeric Systems: 63. † Synthesis of Two Chemically Tanned Gelatin-Based Cryostructurates and Evaluation of Their Potential as Scaffolds for Culturing of Mammalian Cells

Various gelatin-containing gel materials are used as scaffolds for animal and human cell culturing within the fields of cell technologies and tissue engineering. Cryostructuring is a promising technique for the preparation of efficient macroporous scaffolds in biomedical applications. In the current study, two new gelatin-based cryostructurates were synthesized, their physicochemical properties and microstructure were evaluated, and their ability to serve as biocompatible scaffolds for mammalian cells culturing was tested. The preparation procedure included the dissolution of Type A gelatin in water, the addition of urea to inhibit self-gelation, the freezing of such a solution, ice sublimation in vacuo, and urea extraction with ethanol from the freeze-dried matter followed by its cross-linking in an ethanol medium with either carbodiimide or glyoxal. It was shown that in the former case, a denser cross-linked polymer phase was formed, while in the latter case, the macropores in the resultant biopolymer material were wider. The subsequent biotesting of these scaffolds demonstrated their biocompatibility for human mesenchymal stromal cells and HepG2 cells during subcutaneous implantation in rats. Albumin secretion and urea synthesis by HepG2 cells confirmed the possibility of using gelatin cryostructurates for liver tissue engineering.

Designing a Nitro-Induced Sutured Biomacromolecule to Engineer Electroconductive Adhesive Hydrogels

Nitro-functionality, with a large deficit of negative charge, embraces biological importance and has proven its therapeutic essence even in chemotherapy. Functionally, with its strong electron-withdrawing capability, nitro can manipulate the electron density of organic moieties and regulates cellular-biochemical reactions. However, the chemistry of nitro-functionality to introduce physiologically relevant macroscopic properties from the molecular skeleton is unknown. Therefore, herein, a neurotransmitter moiety, dopamine, was chemically modified with a nitro-group to explore its influence on synthesizing a multifunctional biomaterial for therapeutic applications. Chemically, while the nitro-group perturbed the aromatic electron density of nitrocatecholic domain, it facilitated the suturing of nitrocatechol moieties to regain its aromaticity through a radical transfer mechanism, forming a novel macromolecular structure. Incorporation of the sutured-nitrocatecholic strand (S-nCAT) in a gelatin-based hydrogel introduced an electroconductive microenvironment through the delocalization of π-electrons in S-nCAT, while maintaining its catechol-mediated adhesive property for tissue repairing/sealing. Meanwhile, the engineered hydrogel enriched with noncovalent interactions, demonstrated excellent mechano-physical properties to support tissue functions. Cytocompatibility of the bioadhesive was assessed with in vitro and in vivo studies, confirming its potential usage for biomedical applications. In conclusion, this novel chemical approach enabled designing a multifunctional biomaterial by manipulating the electronic properties of small bioactive molecules for various biomedical applications.

3D Polycaprolactone/Gelatin-Oriented Electrospun Scaffolds Promote Periodontal Regeneration

Periodontitis is a worldwide chronic inflammatory disease, where surgical treatment still shows an uncertain prognosis. To break through the dilemma of periodontal treatment, we fabricated a three-dimensional (3D) multilayered scaffold by stacking and fixing electrospun polycaprolactone/gelatin (PCL/Gel) fibrous membranes. The biomaterial displayed good hydrophilic and mechanical properties. Besides, we found human periodontal ligament stem cell (hPDLSC) adhesion and proliferation on it. The following scanning electron microscopy (SEM) and cytoskeleton staining results proved the guiding function of fibers to hPDLSCs. Then, we further analyzed periodontal regeneration-related proteins and mRNA expression between groups. In vivo results in a rat acute periodontal defect model confirmed that the topographic cues of materials could directly guide cellular orientation and might provide the prerequisite for further differentiation. In the aligned scaffold group, besides new bone regeneration, we also observed that angular concentrated fiber regeneration in the root surface of the defect is similar to the normal periodontal tissue. To sum up, we have constructed electrospun membrane-based 3D biological scaffolds, which provided a new treatment strategy for patients undergoing periodontal surgery.

Boron nitride nanotubes reinforced gelatin hydrogel-based ink for bioprinting and tissue engineering applications

The rapid evolution of 3D bioprinting technique, very few biomaterials have been studied and utilised as ink solutions to produce structures. In this work, a polymeric nanocomposite hydrogel-based ink solution was developed using boron nitride nanotubes (BNNTs) reinforced gelatin for 3D bioprinting of scaffolds. The ink solutions and printed scaffolds were characterised for their printability, mechanical, thermal, water uptake, and biological properties (cell viability and inflammation). The viscoelastic behaviour of the scaffolds indicated the increase in storage modulus with an increase in BNNTs composition. Additionally, the compressive strength of the scaffolds increased from 9.43 ± 1.3 kPa to 30.09 ± 1.5 kPa with the addition of BNNTs. Similarly, the thermal stability of the scaffolds enhanced with an increase in BNNTs composition. Furthermore, the scaffolds with a higher concentration of BNNTs displayed resilience in cell culture media at 37 °C for up to 14 days compared with pure gelatin scaffolds. The cell viability results showed a decreased viability rate with an increased concentration of BNNTs scaffolds. However, BNNTs incubated with cells did not display cytokine inflammation. Therefore, this work provides a potential hydrogel-based ink solution for 3D bioprinting of biomimetic tissue constructs with adequate structural stability for a wide range of tissue engineering and regenerative medicine applications.

Stretchable and Electroactive Crosslinked Gelatin for Biodevice and Cell Culture Applications

Biomimetic substrates that incorporate functionality such as electroactivity and mechanical flexibility, find utility in a variety of biomedical applications. Toward these uses, nature-derived materials such as gelatin offer inherent biocompatibility and sustainable sourcing. However, issues such as high swelling, poor mechanical properties, and lack of stability at biological temperatures limit their use. The enzymatic crosslinking of gelatin via microbial transglutaminase (mTG) yields flexible and robust large area substrates that are stable under physiological conditions. Here, we demonstrate the fabrication and characterization of strong, stretchable, conductive mTG crosslinked gelatin thin films. Incorporation of the conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate in the gel matrix with a bioinspired polydopamine surface coating is used to enable conductivity with enhanced mechanical properties such as extensibility and flexibility, in comparison to plain gelatin or crosslinked gelatin films. The electroconductive substrates are conducive to cell growth, supporting myoblast cell adhesion, viability, and proliferation and could find use in creating active cell culture systems incorporating electrical stimulation. The substrates are responsive to motion such as stretching and bending while being extremely handleable and elastic, making them useful for applications such as electronic skin and flexible bioelectronics. Overall, this work presents facile, yet effective development of bioinspired conductive composites as substrates for bio-integrated devices and functional tissue engineering.

Corneal Stroma Regeneration with Collagen-Based Hydrogel as an Artificial Stroma Equivalent: A Comprehensive In Vivo Study

Restoring the anatomical and functional characteristics of the cornea using various biomaterials is especially relevant in the context of a global shortage of donor tissue. Such biomaterials must be biocompatible, strong, and transparent. Here, we report a Viscoll collagen membrane with mechanical and optical properties suitable for replacing damaged stromal tissue. After removing a portion of the stroma, a Viscoll collagen membrane was implanted into the corneas of rabbits. After 6 months, the active migration of host cells into Viscoll collagen membranes was noted, with the preservation of corneal transparency in all experimental animals. Effective integration of the Viscoll collagen membrane with corneal tissue promoted nerve regeneration in vivo, as confirmed by in vivo confocal microscopy. We also demonstrated the safety and efficacy of the Viscoll collagen membrane for corneal stroma regeneration. Thus, in combination with the proposed packaging format that provides long-term storage of up to 10 months, this material has great potential for replacing and regenerating damaged stromal tissues.

Histological Evaluation of the Effect of Local Application of Punica granatum Seed Oil on Bone Healing

Background

Bone healing is a complex and dynamic process that represents a well-orchestrated series of biological events of cellular recruitment, proliferation, and differentiation. The use of medicinal plants in bone healing has attracted increasing interest because of their lower side effects. Punica granatum seed oil (PSO) contains high levels of phenolic compounds, promotes osteoblast function, and plays an important role in bone remodeling. A gelatin sponge (Spongostan) is a hemostatic agent that is extensively applied as scaffolds in engineering and as drug carriers in the medical field. This study aimed to evaluate the effectiveness of PSO for bone healing enhancement. Twenty adult male New Zealand rabbits, weighing an average of 1.5–2 kg, were used in this study. Three intrabony holes were created in the tibiae of each animal, which were filled with a gelatin sponge (GS group) and combined gelatin sponge and PSO (GS/PSO group). Holes without material application were designated as the control group (C group). The animals were sacrificed at the healing duration (2–4 weeks) to prepare bone specimens for histological and histomorphometric analyses.

Results

Histological findings indicated that the bone defects in the GS/PSO group showed more bone formation, mineralization, and maturation compared with the C and GS groups. Multiple group differences for bone cells showed a highly significant difference among all groups in the 2- and 4-week healing periods except for the C/GS and GS/GS/PSO groups at 4-weeks duration. Furthermore, highly significant results were obtained between both durations regarding the trabecular area, trabecular number, and bone marrow area.

Conclusion

The study revealed that the combined application of GS and PSO was more effective in enhancing bone regeneration and accelerating bone healing compared with the other groups.

Tailoring a Gelatin/Agar Matrix for the Synergistic Effect with Cells to Produce High-Quality Cultured Meat

Edible scaffolds are needed in cultured meat to mimic meat's three-dimensional structure by organizing cells and replenishing the insufficient meat mass of cells alone. However, there is still a large gap between slaughtered meat and cells developed into tissues using scaffolds. This is mainly due to the difference in size, texture, flavor, and taste. In this study, we develop a coating matrix to modify the surface of textured vegetable protein (TVP), a vegetable cell support, to produce cultured meat having slaughtered meat's essential characteristics. We optimized the fish gelatin/agar matrix's microstructure by controlling the ratio of the two biopolymers, stably introducing a cell adhesive environment on the TVP. By coating the optimized gelatin/agar matrix on the TVP's surface using an easy and fast dipping method, hybrid cultured meat composed of animal cells and plant protein was produced. As the cells proliferated, their synergistic effect permitted the cultured meat's texture, flavor, and taste to reach a level comparable to that of slaughtered meat. The TVP-based cultured meat prepared with the present technology has been recreated as high-quality cultured meat by satisfying five challenging factors: cells, texture, cost, mass, and flavor.

Properties of New Composite Materials Based on Hydroxyapatite Ceramic and Cross-Linked Gelatin for Biomedical Applications

The main aim of the research was to develop a new biocompatible and injectable composite with the potential for application as a bone-to-implant bonding material or as a bone substitute. A composite based on hydroxyapatite, gelatin, and two various types of commercially available transglutaminase (TgBDF/TgSNF), as a cross-linking agent, was proposed. To evaluate the impacts of composite content and processing parameters on various properties of the material, the following research was performed: the morphology was examined by SEM microscopy, the chemical structure by FTIR spectroscopy, the degradation behavior was examined in simulated body fluid, the injectability test was performed using an automatic syringe pump, the mechanical properties using a nanoindentation technique, the surface wettability was examined by an optical tensiometer, and the cell viability was assayed by MTT and LDH. In all cases, a composite paste was successfully obtained. Injectability varied between 8 and 15 min. The type of transglutaminase did not significantly affect the surface topography or chemical composition. All samples demonstrated proper nanomechanical properties with Young's modulus and the hardness close to the values of natural bone. BDF demonstrated better hydrophilic properties and structural stability over 7 days in comparison with SNF. In all cases, the transglutaminase did not lead to cell necrosis, but cellular proliferation was significantly inhibited, especially for the BDF agent.

Multifunctional chitosan/gelatin@tannic acid cryogels decorated with in situ reduced silver nanoparticles for wound healing

Background

Most traditional wound dressings only partially meet the needs of wound healing because of their single function. Patients usually suffer from the increasing cost of treatment and pain resulting from the frequent changing of wound dressings. Herein, we have developed a mutifunctional cryogel to promote bacterial infected wound healing based on a biocompatible polysaccharide.

Methods

The multifunctional cryogel is made up of a compositive scaffold of chitosan (CS), gelatin (Gel) and tannic acid (TA) and in situ formed silver nanoparticles (Ag NPs). A liver bleeding rat model was used to evaluate the dynamic hemostasis performance of the various cryogels. In order to evaluate the antibacterial properties of the prepared cryogels, gram-positive bacterium Staphylococcus aureus (S. aureus) and gram-negative bacterium Escherichia coli (E. coli) were cultured with the cryogels for 12 h. Meanwhile, S. aureus was introduced to cause bacterial infection in vivo. After treatment for 2 days, the exudates from wound sites were dipped for bacterial colony culture. Subsequently, the anti-inflammatory effect of the various cryogels was evaluated by western blotting and enzyme-linked immunosorbent assay. Finally, full-thickness skin defect models on the back of SD rats were established to assess the wound healing performances of the cryogels.

Results

Due to its porous structure, the multifunctional cryogel showed fast liver hemostasis. The introduced Ag NPs endowed the cryogel with an antibacterial efficiency of >99.9% against both S. aureus and E. coli. Benefited from the polyphenol groups of TA, the cryogel could inhibit nuclear factor-κB nuclear translocation and down-regulate inflammatory cytokines for an anti-inflammatory effect. Meanwhile, excessive reactive oxygen species could also be scavenged effectively. Despite the presence of Ag NPs, the cryogel did not show cytotoxicity and hemolysis. Moreover, in vivo experiments demonstrated that the biocompatible cryogel displayed effective bacterial disinfection and accelerated wound healing.

Conclusions

The multifunctional cryogel, with fast hemostasis, antibacterial and anti-inflammation properties and the ability to promote cell proliferation could be widely applied as a wound dressing for bacterial infected wound healing.

Coacervates: recent developments as nanostructure delivery platforms for therapeutic biomolecules

Coacervation is a liquid-liquid phase separation that can occur in solutions of macromolecules through self-assembly or electrostatic interactions. Recently, coacervates composed of biocompatible macromolecules have been actively investigated as nanostructure platforms to encapsulate and deliver biomolecules such as proteins, RNAs, and DNAs. One particular advantage of coacervates is that they are derived from aqueous solutions, unlike other nanoparticle delivery systems that often require organic solvents. In addition, coacervates achieve high loading while maintaining the viability of the cargo material. Here, we review recent developments in the applications of coacervates and their limitations in the delivery of therapeutic biomolecules. Important factors for coacervation include molecular structures of the polyelectrolytes, mixing ratio, the concentration of polyelectrolytes, and reaction conditions such as ionic strength, pH, and temperature. Various compositions of coacervates have been shown to deliver biomolecules in vitro and in vivo with encouraging activities. However, major hurdles remain for the systemic route of administration other than topical or local delivery. The scale-up of manufacturing methods suitable for preclinical and clinical evaluations remains to be addressed. We conclude with a few research directions to overcome current challenges, which may lead to successful translation into the clinic.

Novel biohybrid spongy scaffolds for fabrication of suturable intraoral graft substitutes

Despite the fact that classic autograft is the gold standard material for periodontal plastic surgery, it has some drawbacks, including the need for a second surgical site and the scarcity of palatal donor tissue. However, only a few research works on the manufacturing of bioengineered intraoral connective tissue grafts have been conducted. In this work, porous bovine serum albumin methacryloyl/gelatin methacryloyl (BG) biohybrid scaffolds were developed for super-elasticity, shape recovery, suturability for persistent stability, sufficient scaffolding function, and convenient manipulating characteristics to fabricate an intraoral graft substitute with superb stability to resist frequent dynamic forces caused by functional movement (speaking, masticating, and swallowing). Furthermore, in a 3D cell culture assay, BG scaffolds demonstrated excellent cell adhesion and proliferation of L929 cells. In addition, the BG scaffolds were able to release Ibuprofen in a controlled manner for postoperative recovery. The use of a low-cost, optimized cryogelation technique for functional biomacromolecules offers up new possibilities to develop promising scaffolds for dental clinical settings.

Gelatin-lecithin-F127 gel mediated self-assembly of curcumin vesicles for enhanced wound healing

Curcumin, a principal component of Curcuma longa, has a long history of being used topically for wound healing. However, poor aqueous solubility of curcumin leads to poor topical absorption. Recently, gelatin based gel has been reported to overcome this issue. However, the release of curcumin from gelatin gel in the bioavailable or easily absorbable form is still a challenge. The present study reports the development of a composite gel prepared from gelatin, F127 and lecithin using temperature dependant gelation and loading of curcumin within it. Notably, the composite gel facilitated the release of curcumin entrapped within vesicles of ~400 nm size. Further, the composite gel exhibited increase in the storage modulus or gel strength, stability, pore size and hydrophobicity as compared to only gelatin gel. Finally, wound healing assay in murine model indicated that curcumin delivered through composite gel showed a significantly faster healing as compared to that delivered through organic solvent. This was also validated by histopathological and biochemical analysis showing better epithelization and collagen synthesis in the group dressed with curcumin containing composite gel. In conclusion, composite gel facilitated the release of bioavailable or easily absorbable curcumin which in turn enhanced the wound healing.

Bioinspired Hydrogels as Platforms for Life-Science Applications: Challenges and Opportunities

Hydrogels, as interconnected networks (polymer mesh; physically, chemically, or dynamic crosslinked networks) incorporating a high amount of water, present structural characteristics similar to soft natural tissue. They enable the diffusion of different molecules (ions, drugs, and grow factors) and have the ability to take over the action of external factors. Their nature provides a wide variety of raw materials and inspiration for functional soft matter obtained by complex mechanisms and hierarchical self-assembly. Over the last decade, many studies focused on developing innovative and high-performance materials, with new or improved functions, by mimicking biological structures at different length scales. Hydrogels with natural or synthetic origin can be engineered as bulk materials, micro- or nanoparticles, patches, membranes, supramolecular pathways, bio-inks, etc. The specific features of hydrogels make them suitable for a wide variety of applications, including tissue engineering scaffolds (repair/regeneration), wound healing, drug delivery carriers, bio-inks, soft robotics, sensors, actuators, catalysis, food safety, and hygiene products. This review is focused on recent advances in the field of bioinspired hydrogels that can serve as platforms for life-science applications. A brief outlook on the actual trends and future directions is also presented.

Biomimetic Organic-Inorganic Nanocomposite Scaffolds to Regenerate Cranial Bone Defects in a Rat Animal Model

While bone regenerates itself after an injury, a critical bone defect requires external interventions. Engineering approaches to restore bone provide a temporary scaffold to support the damage and provide beneficial biological cues for bone repair. Biomimetically generated scaffolds replicate the naturally occurring phenomena in bone regeneration. In this study, a gelatin-calcium phosphate nanocomposite was synthesized by an efficient and cost-effective double-diffusion biomimetic approach. Calcium and phosphate ions are impregnated in the gelatin, mimicking the natural bone mineralization process. Glutaraldehyde from 0.5 to 2 w/v% was used for gelatin cross-linking and mechanical properties of the scaffold, and its biological support for rat bone marrow mesenchymal stromal cells was analyzed. Analysis of scanning electron microscopy images of the nanocomposite scaffolds and Fourier transform infrared (FTIR) and X-ray diffraction (XRD) characterizations of these scaffolds confirmed precipitation of calcium phosphates in the gelatin. Moreover, lysozyme degradation assay showed that scaffold degradation reversely correlates with the concentration of the cross-linking agent. Increased glutaraldehyde concentrations enhanced the mechanical properties of the scaffolds, bringing them closer to those of cancellous bone. Rat bone marrow mesenchymal stromal cells maintained their viability on these scaffolds compared to standard cell culture plates. In addition, these cells showed differentiation into bone lineage as evaluated from alkaline phosphatase activity up to 21 days and Alizarin red staining of the cells over 28 days. Eventually, scaffolds were implanted in a cranial defect in a rat animal model with a 5 mm diameter. Bone regeneration was studied over 90 days. Analysis of histological sections of the injury and computer tomography images revealed that nanocomposite scaffolds cross-linked with 1% w/v glutaraldehyde provide the maximum bone regeneration after 90 days. Collectively, our data show that nanocomposite scaffolds developed here provide effective regeneration for extensive bone defects in vivo.

Multi-crosslinked hydrogels with instant self-healing and tissue adhesive properties for biomedical applications

Due to the defects like long gelling time, inferior mechanical properties and weak adhesion, in-situ forming hydrogels are still restricted in biomedical applications like viscera rupture and targeted therapy. To address these problems, a new kind of multi-crosslinked hydrogel (G-OKG-DA) consisting of gelatin, oxidized konjac glucomannan (OKG), and dopamine (DA) is proposed in this study. The resulting hybrid hydrogel is endowed with a short gelling time (about 3 min) and injectable capacity. According to the mechanical and adhesive tests, G-OKG-DA hydrogel shows a robust tensile strength of 23.94 kPa, as well as a higher adhesive strength (around 150 kPa) than commercial fibrin glue. In addition, an instant self-healing behavior of G-OKG-DA hydrogel can be found, which is attributed to multi-crosslinking reactions including Schiff-base dynamic covalent bonds between OKG and gelatin, oxidative polymerization of DA, and catechol-mediated chemistry like Michael addition and DA-quinone coupling. Importantly, the multi-crosslinked hydrogel will not compromise its hemocompatibility and cytocompatibility in vitro, suggesting potential applications in biomedical fields as tissue adhesive and implants. This article is protected by copyright. All rights reserved.

Microbial Transglutaminase Improves ex vivo Adhesion of Gelatin Methacryloyl Hydrogels to Human Cartilage

Current surgical techniques to treat articular cartilage defects fail to produce a satisfactory long-term repair of the tissue. Regenerative approaches show promise in their ability to generate hyaline cartilage using biomaterials in combination with stem cells. However, the difficulty of seamlessly integrating the newly generated cartilage with the surrounding tissue remains a likely cause of long-term failure. To begin to address this integration issue, our strategy exploits a biological enzyme (microbial transglutaminase) to effect bioadhesion of a gelatin methacryloyl implant to host tissue. Mechanical characterization of the bioadhesive material shows that enzymatic crosslinking is compatible with photocrosslinking, allowing for a dual-crosslinked system with improved mechanical properties, and a slower degradation rate. Biocompatibility is illustrated with a 3D study of the metabolic activity of encapsulated human adipose derived stem cells. Furthermore, enzymatic crosslinking induced by transglutaminase is not prevented by the presence of cells, as measured by the bulk modulus of the material. Adhesion to human cartilage is demonstrated ex vivo with a significant increase in adhesive strength (5.82 ± 1.4 kPa as compared to 2.87 ± 0.9 kPa, p < 0.01) due to the addition of transglutaminase. For the first time, we have characterized a bioadhesive material composed of microbial transglutaminase and GelMA that can encapsulate cells, be photo crosslinked, and bond to host cartilage, taking a step toward the integration of regenerative implants.