Nanomaterials-combined methacrylated gelatin hydrogels (GelMA) for cardiac tissue constructs

3D-printed multifunctional bilayer scaffold with sustained release of apoptotic extracellular vesicles and antibacterial coacervates for enhanced wound healing

Full-thickness skin defects pose significant challenges to physical and psychological health while traditional skin grafting techniques are associated with limitations. Herein, we present a 3D-printed multifunctional bilayer scaffold that incorporates apoptotic extracellular vesicles (ApoEVs) and antibacterial coacervates to prevent wound infection and promote wound healing. The ApoEVs were continuously released from the lower layer of the scaffold with large pores to promote angiogenesis and collagen deposition. Meanwhile, the pH-responsive curcumin-containing coacervates were released from the upper layer of the scaffold with dense pores to exert antibacterial and reactive oxygen species scavenging ability. In vivo experiments showed that the scaffold accelerated wound healing and improved healing quality by promoting a more organized collagen arrangement and reducing hyperplastic scar tissue. Furthermore, it effectively reduced hyperplastic scar tissue, resulting in a decrease in the average scar area from 73.3 % to 19.9 %. RNA sequencing analysis revealed that the scaffold upregulated genes associated with cell proliferation and downregulated genes related to inflammation, indicating its potential therapeutic applications for wound healing. This multifunctional bilayer scaffold represents a promising candidate for the treatment of full-thickness skin defects, offering rationales for designing skin scaffolds for regenerative medicine applications.

3D pancreatic ductal adenocarcinoma desmoplastic model: Glycolysis facilitating stemness via ITGAV-PI3K-AKT-YAP1

The distinctive desmoplastic tumor microenvironment (TME) of pancreatic ductal adenocarcinoma (PDAC) is crucial in determining the stemness of tumor cells. And the conventional two-dimensional (2D) culture does not adequately mimic the TME. Therefore, a three-dimensional (3D) PDAC desmoplastic model was constructed using GelMA and HAMA, which provides benefits in terms of simulating both the main components (COL and HA) and the crosslinking of the extracellular matrix. We found that the 3D PDAC desmoplastic model upregulated the expression of the markers for stemness (NANOG and OCT4) and glycolysis (HK2 and GLUT2), and elevated the level of glycolysis, including increased glucose consumption and lactic acid production. Additionally, YAP1 played a crucial role in promoting glycolysis, which boosted stemness. Furthermore, RNA sequencing (RNA-seq) was employed to explore the underlying mechanisms associated with stemness within the 3D desmoplastic model. Subsequent KEGG pathway analysis indicated the activation of the PI3K-AKT signaling pathway, providing insights into the molecular processes at play. Using bioinformatics, qRT-PCR and western blot, we proposed that ITGAV-PI3K-AKT-YAP1 axis may account for the glycolysis mediated the stemness. Collectively, the 3D desmoplastic model may serve as a new platform for understanding the underlying mechanism by which the TME induces stemness.

Enhancement of alginate/gelatin/polyvinyl alcohol hydrogels for multi-crosslinked 3D printed blood vessels

Given the significant social and clinical challenges posed by the increasing incidence of cardiovascular diseases (CVDs), the development of small-diameter artificial blood vessels utilizing biomacromolecular materials has emerged as a promising therapeutic strategy for addressing CVDs. In this paper, sodium alginate/gelatin/polyvinyl alcohol (SA/Gel/PVA) porous composite hydrogel ink is firstly prepared by multiple crosslinking method, aiming to solve the problems of poor mechanical properties and unsatisfactory printing effect of small diameter blood vessels. The effect of crosslinking order on the mechanical properties of the materials is explored by adjusting the ratio of SA/Gel/PVA hydrogel. In results, the mechanical strength (>20 %), swelling property (>250 %) and water content (>81 %) of the materials can be improved by appropriate crosslinking method and concentration ratio. Through comprehensive characterization encompassing mechanical properties, moisture content, and microscopic morphology analysis, this study investigates the influence of microscopic pore architecture on the physicochemical characteristics of hybrid hydrogels, aiming to optimize the hydrogel formulation for enhanced performance. Finally, the self-developed 3D printing equipment is utilized to verify the printing feasibility. This study can not only advance the performance of SA/Gel/PVA hydrogel, but also further advance the application of SA/Gel/PVA hydrogel in the field of vessel printing and molding.

Predicting rheological properties of HAMA/GelMA hybrid hydrogels via machine learning

- Rheological properties are pivotal in determining the printability of biomaterials, directly impacting the success of 3D bioprinted constructs. Understanding the intricate relationship between biomaterial formulations, rheological behavior and printability can facilitate the advancement and rapid development of biomaterials. Herein, we critically measured the rheological properties of hyaluronic acid methacrylate (HAMA)/gelatin methacrylate (GelMA) hybrid hydrogels with varied formulations and generated a dataset to train a machine learning (ML) model. By utilizing four well-known algorithms, we developed the ML model for the viscosity and shear stress of HAMA/GelMA hydrogel mixtures. To improve model interpretability, we further created a multilayer perceptron framed model, known as HydroThermoMLP, by incorporating the Redlich-Kister polynomial as the thermodynamic representation of viscosity of mixtures. To accomplish the MLP learning on limited data, the shared loss function was formulated on the basis of the R-K presentation to guide the joint training process. The established HydroThermoMLP model, while maintaining the same accuracy as Random Forest, produces outputs that adhere to thermodynamic constraints and instill confidence in generalization applications with a simple algorithm informed by the R-K polynomial. It presents a robust predictive ML tool to forecast the viscosity of hybrid hydrogels and direct the design of biomaterials while appropriately abiding by thermodynamic constraints as essential guidelines.

Paintable, Fast Gelation, Highly Adhesive Hydrogels for High-fidelity Electrophysiological Monitoring Wirelessly

High-fidelity wireless electrophysiological monitoring is essential for ambulatory healthcare applications. Soft solid-like hydrogels have received significant attention as epidermal electrodes because of their tissue-like mechanical properties and high biocompatibility. However, it is challenging to develop a hydrogel electrode that provides robust contact and high adhesiveness with glabrous skin and hairy scalp for high-fidelity, continuous electrophysiological signal detection. Here, a paintable, fast gelation, highly adhesive, and conductive hydrogel is engineered for high-fidelity wireless electrophysiological monitoring. The hydrogel, consisting of gelatin, gallic acid, sodium citrate, lithium chloride, glycerol, and Tris-HCl buffer solution exhibits a reversible thermal phase transition capability, which endows it with the attributes of on-skin applicability and fast in situ gelation with 15 s, thereby addressing the aforementioned limitations. The introduction of gallic acid enhances the adhesive properties of the hydrogel, facilitating secure electrode attachment to the skin or hairy scalp. To accentuate the potential applications in at-home electrophysiological health monitoring, the hydrogel electrodes are demonstrated for high-fidelity electrocardiogram recording for one hour during various daily activities, as well as in simultaneous electroencephalogram and electrocardiogram recording during a 30 min nap.

Integration of Hydrogels and 3D Bioprinting Technologies for Chronic Wound Healing Management

The integration of hydrogel-based bioinks with 3D bioprinting technologies presents an innovative approach to chronic wound management, which is particularly challenging to treat because of its multifactorial nature and high risk of complications. Using precise deposition techniques, 3D bioprinting significantly alters traditional wound care paradigms by enabling the fabrication of patient-specific wound dressings that imitate natural tissue properties. Hydrogels are notably beneficial for these applications because of their abundant water content and mechanical properties, which promote cell viability and pathophysiological processes of wound healing, such as re-epithelialization and angiogenesis. This article reviews key 3D printing technologies and their significance in enhancing the structural and functional outcomes of wound-care solutions. Challenges in bioink viscosity, cell viability, and printability are addressed, along with discussions on the cross-linking and mechanical stability of the constructs. The potential of 3D bioprinting to revolutionize chronic wound management rests on its capacity to generate remedies that expedite healing and minimize infection risks. Nevertheless, further studies and clinical trials are necessary to advance these therapies from laboratory to clinical use.

Dynamic composite hydrogels of gelatin methacryloyl (GelMA) with supramolecular fibers for tissue engineering applications

In the field of tissue engineering, there is a growing need for biomaterials with structural properties that replicate the native characteristics of the extracellular matrix (ECM). It is important to include fibrous structures into ECM mimics, especially when constructing scar models. Additionally, including a dynamic aspect to cell-laden biomaterials is particularly interesting, since native ECM is constantly reshaped by cells. Composite hydrogels are developed to bring different combinations of structures and properties to a scaffold by using different types and sources of materials. In this work, we aimed to combine gelatin methacryloyl (GelMA) with biocompatible supramolecular fibers made of a small self-assembling sugar-derived molecule (N-heptyl-D-galactonamide, GalC7). The GalC7 fibers were directly grown in the GelMA through a thermal process, and it was shown that the presence of the fibrous network increased the Young's modulus of GelMA. Due to the non-covalent interactions that govern the self-assembly, these fibers were observed to dissolve over time, leading to a dynamic softening of the composite gels. Cardiac fibroblast cells were successfully encapsulated into composite gels for 7 days, showing excellent biocompatibility and fibroblasts extending in an elongated morphology, most likely in the channels left by the fibers after their degradation. These novel composite hydrogels present unique properties and could be used as tools to study biological processes such as fibrosis, vascularization and invasion.

Injectable Inflammation-Responsive Hydrogels for Microenvironmental Regulation of Intervertebral Disc Degeneration

Chronic local inflammation and excessive cell apoptosis in nucleus pulposus (NP) tissue are the main causes of intervertebral disc degeneration (IDD). Stimuli-responsive hydrogels have great potential in the treatment of IDD by facilitating localized and controlled drug delivery. Herein, an injectable drug-loaded dual stimuli-responsive adhesive hydrogel for microenvironmental regulation of IDD, is developed. The gelatin methacryloyl is functionalized with phenylboronic acid groups to enhance drug loading capacity and enable dual stimuli-responsive behavior, while the incorporation of oxidized hyaluronic acid further improves the adhesive properties. The prepared hydrogel exhibits an enhanced drug loading capacity for diol-containing drugs, pH- and reactive oxygen species (ROS)-responsive behaviors, excellent radical scavenging efficiency, potent antibacterial activity, and favorable biocompatibility. Furthermore, the hydrogel shows a beneficial protective efficacy on NP cells within an in vitro oxidative stress microenvironment. The in vivo results demonstrate the hydrogel's excellent therapeutic effect on treating IDD by maintaining water retention, restoring disc height, and promoting NP regeneration, indicating that this hydrogel holds great potential as a promising therapeutic approach for regulating the microenvironment and alleviating the progression of IDD.

Hydrogels for Cardio and Vascular Tissue Repair and Regeneration

Cardiovascular disease (CVD), the leading cause of death globally, affects the heart and arteries with a variety of clinical manifestations, the most dramatic of which are myocardial infarction (MI), abdominal aortic aneurysm (AAA), and intracranial aneurysm (IA) rupture. In MI, necrosis of the myocardium, scar formation, and loss of cardiomyocytes result from insufficient blood supply due to coronary artery occlusion. Beyond stenosis, the arteries that are structurally and functionally connected to the cardiac tissue can undergo pathological dilation, i.e., aneurysmal dilation, with high risk of rupture. Aneurysms of the intracranial arteries (IAs) are more commonly seen in young adults, whereas those of the abdominal aorta (AAA) are predominantly seen in the elderly. IAs, unpredictably, can undergo rupture and cause life-threatening hemorrhage, while AAAs can result in rupture, internal bleeding and high mortality rate. In this clinical context, hydrogels, three-dimensional networks of water-seizing polymers, have emerged as promising biomaterials for cardiovascular tissue repair or protection due to their biocompatibility, tunable properties, and ability to encapsulate and release bioactive molecules. This review provides an overview of the current state of research on the use of hydrogels as an innovative platform to promote cardiovascular-specific tissue repair in MI and functional recovery or protection in aneurysmal dilation.