Mechanical Properties Of Hydrogels Research Articles

A multicrosslinked network composite hydrogel scaffold based on DLP photocuring printing for nasal cartilage repair.

Natural hydrogels are widely employed in tissue engineering and have excellent biodegradability and biocompatibility. Unfortunately, the utilization of such hydrogels in the field of three-dimensional (3D) printing nasal cartilage is constrained by their subpar mechanical characteristics. In this study, we provide a multicrosslinked network hybrid ink made of photocurable gelatin, hyaluronic acid, and acrylamide (AM). The ink may be processed into intricate 3D hydrogel structures with good biocompatibility and high stiffness properties using 3D printing technology based on digital light processing (DLP), including intricate shapes resembling noses. By varying the AM content, the mechanical behavior and biocompatibility of the hydrogels can be adjusted. In comparison to the gelatin methacryloyl (GelMA)/hyaluronic acid methacryloyl (HAMA) hydrogel, adding AM considerably enhances the hydrogel's mechanical properties while also enhancing printing quality. Meanwhile, the biocompatibility of the multicrosslinked network hydrogels and the development of cartilage were assessed using neonatal Sprague-Dawley (SD) rat chondrocytes (CChons). Cells sown on the hydrogels considerably multiplied after 7 days of culture and kept up the expression of particular proteins. Together, our findings point to GelMA/HAMA/polyacrylamide (PAM) hydrogel as a potential material for nasal cartilage restoration. The photocuring multicrosslinked network ink composed of appropriate proportions of GelMA/HAMA/PAM is very suitable for DLP 3D printing and will play an important role in the construction of nasal cartilage, ear cartilage, articular cartilage, and other tissues and organs in the future. Notably, previous studies have not explored the application of 3D-printed GelMA/HAMA/PAM hydrogels for nasal cartilage regeneration.

Correlation between synthesis parameters and hyperelasticity of hydrogels: Experimental investigation and theoretical modeling

The mechanical properties of hydrogels are significantly influenced by synthesis parameters. Although the mapping from the space of synthesis parameters to the space of properties has been investigated experimentally, a quantitative theoretical framework is still lacking. In this work, the effect of synthesis parameters on the hyperelastic behaviors of hydrogels was experimentally studied. Subsequently, we conducted theoretical analysis by combining the constitutive model and polymer physics to quantify the correlation between synthesis parameters (the initial water content, current water content, and degree of cross-linking) and hyperelasticity (the elastic modulus, degree of entanglement, and stress-stretch ratio curve) of hydrogels. The internal relation between critical polymer content for entanglement and both the initial water content and degree of cross-linking arises from the scaling laws. By analyzing the critical polymer content for entanglement and comparing it with the current polymer content, hydrogels are categorized as either cross-linking-dominated or entanglement-dominated. The current study indicates that a low degree of cross-linking, i.e., a long-chain structure, is an important prerequisite for plenty of entanglements. Hydrogels with low cross-linking are highly entangled, whether they possess high initial water content/low current water content or low initial water content/high current water content. This work paves the way for the systematic design of synthesis parameters, thereby guiding the modulation and optimization of the overall mechanical properties and the application of hydrogels.

Contactless magnetically responsive injectable hydrogel for aligned tissue regeneration

Cellular alignment plays a pivotal role in several human tissues, including skeletal muscle, spinal cord and tendon. Various techniques have been developed to control cellular alignment using 3D biomaterials. However, the majority of 3D-aligned scaffolds require invasive surgery for implantation. In contrast, injectable hydrogels provide a non-invasive delivery method, gaining considerable attention for the treatment of diverse conditions, including osteochondral lesions, volumetric muscle loss, and traumatic brain injury.We engineered a biomimetic hydrogel with magnetic responsiveness by combining gellan gum, hyaluronic acid, collagen, and magnetic nanoparticles (MNPs). Collagen type I was paired with MNPs to form magnetic collagen bundles (MCollB), allowing the orientation control of these bundles within the hydrogel matrix through the application of a remote low-intensity magnetic field. This resulted in the creation of an anisotropic architecture. The hydrogel mechanical properties were comparable to those of human soft tissues, such as skeletal muscle, and proof of the aligned hydrogel concept was demonstrated.In vitro findings confirmed the absence of toxicity and pro-inflammatory effects. Notably, an increased fibroblast cell proliferation and pro-regenerative activation of macrophages were observed. The in-vivo study further validated the hydrogel biocompatibility and demonstrated the feasibility of injection with rapid in situ gelation. Consequently, this magnetically controlled injectable hydrogel exhibits significant promise as a minimally invasive, rapid gelling and effective treatment for regenerating various aligned human tissues.

Polydopamine-intercalated montmorillonite to mitigate polymerization inhibition for preparation of photothermal antibacterial and hemostatic hydrogel

The mechanical properties of hydrogels with in situ introduced polydopamine (PDA) will always be unsatisfactory owing to the polymerization inhibition of the catechol structure. Therefore, it is necessary to find a way to mitigate the inhibition. In this work, PDA-inserted montmorillonite (MMT) was first prepared. The micro-spacing of the MMT nanolayers limited the oxygen content which prevented the complete oxidation of the dopamine adsorbed between the MMT nanosheet layers and retained the catechol moiety. Then, polydopamine montmorillonite polyacrylamide (PMP) hydrogel was prepared under green LED irradiation. The hydrogel exhibited excellent mechanical properties and adhesive strength, as well as excellent photothermal properties and antimicrobial ability. After irradiation by NIR laser, the PMP hydrogel can be heated up and maintained at 50 ℃ within 2 min, and the antimicrobial rate reached 98 %. Meanwhile, PMP hydrogel presents excellent biocompatibility and hemostatic ability. Therefore, PMP hydrogel has a great potential in the field of photothermal therapy and hemostasis.

Effect of Peptide-Polymer Host-Guest Electrostatic Interactions on Self-Assembling Peptide Hydrogels Structural and Mechanical Properties and Polymer Diffusivity.

Peptide-based supramolecular hydrogels are an attractive class of soft materials for biomedical applications when biocompatibility is a key requirement as they exploit the physical self-assembly of short self-assembling peptides avoiding the need for chemical cross-linking. Based on the knowledge developed through our previous work, we designed two novel peptides, E(FKFE)2 and K(FEFK)2, that form transparent hydrogels at pH 7. We characterized the phase behavior of these peptides and showed the clear link that exists between the charge carried by the peptides and the physical state of the samples. We subsequently demonstrate the cytocompatibility of the hydrogel and its suitability for 3D cell culture using 3T3 fibroblasts and human mesenchymal stem cells. We then loaded the hydrogels with two polymers, poly-l-lysine and dextran. When polymer and peptide fibers carry opposite charges, the size of the elemental fibril formed decreases, while the overall level of fiber aggregation and fiber bundle formation increases. This overall network topology change, and increase in cross-link stability and density, leads to an overall increase in the hydrogel mechanical properties and stability, i.e., resistance to swelling when placed in excess media. Finally, we investigate the diffusion of the polymers out of the hydrogels and show how electrostatic interactions can be used to control the release of large molecules. The work clearly shows how polymers can be used to tailor the properties of peptide hydrogels through guided intermolecular interactions and demonstrates the potential of these new soft hydrogels for use in the biomedical field in particular for delivery or large molecular payloads and cells as well as scaffolds for 3D cell culture.

Rationally designed β-cyclodextrin-crosslinked polyacrylamide hydrogels for cell spheroid formation and 3D tumor model construction

In vitro tumor models are essential for understanding tumor behavior and evaluating tumor biological properties. Hydrogels that can mimic the tumor extracellular matrix have become popular for creating 3D in vitro tumor models. However, designing biocompatible hydrogels with appropriate chemical and physical properties for constructing tumor models is still a challenge. In this study, we synthesized a series of β-cyclodextrin (β-CD)-crosslinked polyacrylamide hydrogels with different β-CD densities and mechanical properties and evaluated their potential for use in 3D in vitro tumor model construction, including cell capture and spheroid formation. By utilizing a combination of β-CD-methacrylate (CD-MA) and a small amount of N,N′-methylene bisacrylamide (BIS) as hydrogel crosslinkers and optimizing the CD-MA/BIS ratio, the hydrogels performed excellently for tumor cell 3D culture and spheroid formation. Notably, when we co-cultured L929 fibroblasts with HeLa tumor cells on the hydrogel surface, co-cultured spheroids were formed, showing that the hydrogel can mimic the complexity of the tumor extracellular matrix. This comprehensive investigation of the relationship between hydrogel mechanical properties and biocompatibility provides important insights for hydrogel-based in vitro tumor modeling and advances our understanding of the mechanisms underlying tumor growth and progression.

Cotton Fabric-Reinforced Hydrogels with Excellent Mechanical and Broad-Spectrum Photothermal Antibacterial Properties.

Antibacterial hydrogel wound dressings hold great potential in eliminating bacteria and accelerating the healing process. However, it remains a challenge to fabricate hydrogel wound dressings that simultaneously exhibit excellent mechanical and photothermal antibacterial properties. Here we report the development of polydopamine-functionalized graphene oxide (rGO@PDA)/calcium alginate (CA)/Polypyrrole (PPy) cotton fabric-reinforced hydrogels (abbreviated as rGO@PDA/CA/PPy FHs) for tackling bacterial infections. The mechanical properties of hydrogels were greatly enhanced by cotton fabric reinforcement and an interpenetrating structure, while excellent broad-spectrum photothermal antibacterial properties based on the photothermal effect were obtained by incorporating PPy and rGO@PDA. Results indicated that rGO@PDA/CA/PPy FHs exhibited superior tensile strength in both the warp (289 ± 62.1 N) and weft directions (142 ± 23.0 N), similarly to cotton fabric. By incorporating PPy and rGO@PDA, the swelling ratio was significantly decreased from 673.5% to 236.6%, while photothermal conversion performance was significantly enhanced with a temperature elevated to 45.0 °C. Due to the synergistic photothermal properties of rGO@PDA and PPy, rGO@PDA/CA/PPy FHs exhibited excellent bacteria-eliminating efficiency for S. aureus (0.57%) and E. coli (3.58%) after exposure to NIR for 20 min. We believe that the design of fabric-reinforced hydrogels could serve as a guideline for developing hydrogel wound dressings with improved mechanical properties and broad-spectrum photothermal antibacterial properties for infected-wound treatment.

Tailoring Network Topology in Mechanically Robust Hydrogels for 3D Printing and Injection.

Tissue engineering and regenerative medicine are confronted with a persistent challenge: the urgent demand for robust, load-bearing, and biocompatible scaffolds that can effectively endure substantial deformation. Given that inadequate mechanical performance is typically rooted in structural deficiencies─specifically, the absence of energy dissipation mechanisms and network uniformity─a crucial step toward solving this problem is generating synthetic approaches that enable exquisite control over network architecture. This work systematically explores structure-property relationships in poly(ethylene glycol)-based hydrogels constructed utilizing thiol-yne chemistry. We systematically vary polymer concentration, constituent molar mass, and cross-linking protocols to understand the impact of architecture on hydrogel mechanical properties. The network architecture was resolved within the molecular model of Rubinstein-Panyukov to obtain the densities of chemical cross-links and entanglements. We employed both nucleophilic and radical pathways, uncovering notable differences in mechanical response, which highlight a remarkable degree of versatility achievable by tuning readily accessible parameters. Our approach yielded hydrogels with good cell viability and remarkably robust tensile and compression profiles. Finally, the hydrogels are shown to be amenable to advanced processing techniques by demonstrating injection- and extrusion-based 3D printing. Tuning the mechanism and network regularity during the cell-compatible formation of hydrogels is an emerging strategy to control the properties and processability of hydrogel biomaterials by making simple and rational design choices.

A Spontaneous In Situ Thiol-Ene Crosslinking Hydrogel with Thermo-Responsive Mechanical Properties.

The thermo-responsive behavior of Poly(N-isopropylacrylamide) makes it an ideal candidate to easily embed cells and allows the polymer mixture to be injected. However, P(NiPAAm) hydrogels possess minor mechanical properties. To increase the mechanical properties, a covalent bond is introduced into the P(NIPAAm) network through a biocompatible thiol-ene click-reaction by mixing two polymer solutions. Co-polymers with variable thiol or acrylate groups to thermo-responsive co-monomer ratios, ranging from 1% to 10%, were synthesized. Precise control of the crosslink density allowed customization of the hydrogel's mechanical properties to match different tissue stiffness levels. Increasing the temperature of the hydrogel above its transition temperature of 31 °C induced the formation of additional physical interactions. These additional interactions both further increased the stiffness of the material and impacted its relaxation behavior. The developed optimized hydrogels reach stiffnesses more than ten times higher compared to the state of the art using similar polymers. Furthermore, when adding cells to the precursor polymer solutions, homogeneous thermo-responsive hydrogels with good cell viability were created upon mixing. In future work, the influence of the mechanical micro-environment on the cell's behavior can be studied in vitro in a continuous manner by changing the incubation temperature.

Bioinspired 3D printed elastomer-hydrogel hybrid with robust interfacial bonding for flexible ionotronics

Hydrogels are widely used in flexible ionotronics due to their continuous conductive phase and good biocompatibility. However, their poor mechanical properties affect their stability and lifespan. It is a significant challenge to prepare hydrogels with both high conductivity and mechanical strength, as improving the mechanical properties often results in a tighter network, which reduces electrical conductivity. Human skin is composed of a stiff collagen fibril scaffold for resisting external damage, and a soft matrix that detect various stimuli through ion transport. Herein, inspired by the structure of human skin, a hydrogel composite with remarkable mechanical properties, high ionic conductivity, and self-healing property is prepared. The composite structure with 3D printed elastomeric skeleton and hydrogel matrix, addresses both the contradiction between the ionic conductivity and mechanical properties of hydrogels, as well as the difficulty of realizing complex macrostructures of the skeleton. The issue of weak interface in composites is resolved by creating interfacial covalent bonds. The composite’s self-healing property, combined with a robust interface, ensure the stability and longevity of the composite when used as flexible sensors. This novel approach of creating robust interface is also employed in the encapsulation of hydrogels and the fabrication of flexible microcircuits.

Preparation and evaluation of chitosan/MCM-41-based spongy hydrogels loaded with tea tree oil

In this study, chitosan, polyvinyl alcohol, gelatin, MCM-41 and tea tree oil (TTO) were used as raw materials. MCM-41-based spongy hydrogels loaded with TTO were synthesized by physical cross-linking method. The TTO was first adsorbed into MCM-41 s. Then different contents of MCM-41 s were added to the hydrogel, which affected the properties of the hydrogel. The structure of hydrogels was analyzed by scanning electron microscopy (SEM) and attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The mechanical properties of hydrogels were determined by swelling, degradation and ductility evaluation. The antibacterial effect and biocompatibility were determined by in vitro antibacterial and cytotoxicity examinations. In this study, the mechanical property of the hydrogels was enhanced with the increasing content of MCM-41 s. The hydrogels exhibited an excellent antibacterial effect attributed to the synergistic interaction between TTO and chitosan. Furthermore, the hydrogels showed superior biocompatibility property. In conclusion, the hydrogels prepared in this study have great potential for expanding their applications in the bacteriostatic field.

Evaluation of gelatin bloom strength on gelatin methacryloyl hydrogel properties

Gelatin methacryloyl (GelMA) hydrogels are widely used for a variety of tissue engineering applications. The properties of gelatin can affect the mechanical properties of gelatin gels; however, the role of gelatin properties such as bloom strength on GelMA hydrogels has not yet been explored. Bloom strength is a food industry standard for describing the quality of gelatin, where higher bloom strength is associated with higher gelatin molecular weight. Here, we evaluate the role of bloom strength on GelMA hydrogel mechanical properties. We determined that both bloom strength of gelatin and weight percent of GelMA influenced both stiffness and viscoelastic ratio; however, only bloom strength affected diffusivity, permeability, and pore size. With this library of GelMA hydrogels of varying properties, we then encapsulated Swan71 trophoblast spheroids in these hydrogel variants to assess how bloom strength affects trophoblast spheroid morphology. Overall, we observed a decreasing trend of spheroid area and Feret diameter as bloom strength increased. In identifying clear relationships between bloom strength, hydrogel mechanical properties, and trophoblast spheroid morphology, we demonstrate that bloom strength should considered when designing tissue engineered constructs.

Fibrin-Based Hydrogels with Reactive Amphiphilic Copolymers for Mechanical Adjustments Allow for Capillary Formation in 2D and 3D Environments.

This study focuses on enhancing controllable fibrin-based hydrogels for tissue engineering, addressing existing weaknesses. By integrating a novel copolymer, we improved the foundation for cell-based angiogenesis with adaptable structural features. Tissue engineering often faces challenges like waste disposal and nutrient supply beyond the 200 µm diffusion limit. Angiogenesis breaks through this limitation, allowing the construction of larger constructs. Our innovative scaffold combination significantly boosts angiogenesis, resulting in longer branches and more capillary network junctions. The copolymer attached to fibrin fibers enables precise adjustment of hydrogel mechanical dynamic properties for specific applications. Our material proves effective for angiogenesis, even under suppression factors like suramin. In our study, we prepared fibrin-based hydrogels with and without the copolymer PVP12400-co-GMA10mol%. Using a co-culture system of human umbilical vein endothelial cells (HUVEC) and mesenchymal stem cells (MSC), we analyzed angiogenetic behavior on and within the modified hydrogels. Capillary-like structures were reproducibly formed on different surfaces, demonstrating the general feasibility of three-dimensional endothelial cell networks in fibrin-based hydrogels. This highlights the biomaterial's suitability for in vitro pre-vascularization of biohybrid implants.

A well plate-based GelMA photo-crosslinking system with tunable hydrogel mechanical properties to regulate the PTH-mediated osteogenic fate

Versatile and efficient regulation of the mechanical properties of the extracellular matrix is crucial not only for understanding the dynamic changes in biological systems, but also for obtaining precise and effective cellular responses in drug testing. In this study, we developed a well plate-based hydrogel photo-crosslinking system to effectively control the mechanical properties of hydrogels and perform high-throughput assays. We improved cell biocompatibility by using gelatin methacryloyl (GelMA) with a visible light photo-crosslinking method. Multiple cell-laden GelMA hydrogels were simultaneously and uniformly created using multi-arrayed 520 nm light-emitting diodes in a well plate format. The elastic modulus of the hydrogels can be widely adjusted (0.5–30 kPa) using a photo-crosslinking system capable of independently controlling the light intensity or exposure time for multiple samples. We demonstrate the feasibility of our system by observing enhanced bone differentiation of human mesenchymal stem cells (hMSCs) cultured on stiffer hydrogels. Additionally, we observed that the osteogenic fate of hMSCs, affected by the different mechanical properties of the gel, was regulated by parathyroid hormone (PTH). Notably, in response to PTH, hMSCs in a high-stiffness microenvironment upregulate osteogenic differentiation while exhibiting increased proliferation in a low-stiffness microenvironment. Overall, the developed system enables the generation of multiple cell-laden three-dimensional cell culture models with diverse mechanical properties and holds significant potential for expansion into drug testing.

The Formulation and Characterization of Wound Dressing Releasing S-Nitrosoglutathione from Polyvinyl Alcohol/Borax Reinforced Carboxymethyl Chitosan Self-Healing Hydrogel.

Self-healing hydrogels often lack mechanical properties, limiting their wound-dressing applications. This study introduced S-Nitrosoglutathione (GSNO) to self-healing hydrogel-based wound dressings. Self-healing hydrogel mechanical properties were improved via polymer blends. Applying this hydrogel to the wound site allows it to self-heal and reattach after mechanical damage. This work evaluated polyvinyl alcohol (PVA)-based self-healing hydrogels with borax as a crosslinking agent and carboxymethyl chitosan as a mechanical property enhancer. Three formulations (F1, F4, and F7) developed self-healing hydrogels. These formulations had borax concentrations of 0.8%, 1.2%, and 1.6%. An FTIR study shows that borate ester crosslinking and hydrogen bonding between polymers generate a self-healing hydrogel. F4 has a highly uniform and regular pore structure, as shown by the scanning electron microscope image. F1 exhibited faster self-healing, taking 13.95 ± 1.45 min compared to other formulations. All preparations had pH values close to neutrality, making them suitable wound dressings. Formula F7 has a high drug content (97.34 ± 1.21%). Good mechanical qualities included high tensile stress-strain intensity and Young's modulus. After 28 h of storage at -20 °C, 5 °C, and 25 °C, the self-healing hydrogel's drug content dropped significantly. The Korsmeyer-Peppas release model showed that the release profile of GSNO followed Fickian diffusion. Thus, varying the concentration of crosslinking agent and adding a polymer affects self-healing hydrogels' physicochemical properties.

Sodium lignosulfonate doped polyvinyl alcohol-based hydrogel conductive composites based on ion-specific effects with continuously tunable mechanical properties and excellent conductive sensing properties

Hydrogels have great application prospects in the fields of bionics, soft tissue probes, and motion detection, etc. However, the high water content and loose cross-linker structure of hydrogels lead to weak mechanical properties, which limits their application and development. Therefore, in this study, sodium lignosulfonate doped polyvinyl alcohol hydrogels (PVA/LS) were constructed using polyvinyl alcohol as the matrix and sodium lignosulfonate as the filler; the hydrogels were also treated with different ionic solutions to construct ion-responsive hydrogels (PVA/LS/ION); and ion-conducting hydrogels (PVA/LS/CL) were constructed by the change of the concentration of sodium chloride (NaCl) solution. The hydrophilicity of the polyvinyl alcohol (PVA) molecular chain was changed by different ions, resulting in either water absorption (salting in) or dehydration (salting out), and the hydrogel mechanical properties could be adjusted over a wide range (tensile strength: 77 kPa ∼ 3.26 MPa; elongation at break: 290 ∼ 870%; modulus: 24 ∼ 563 kPa; toughness: 96 kJ/m3 ∼ 14.1 MJ/m3). In addition, the hydrogels have good conductivity regulation (1.09 ∼ 2.72 S/m) and sensing properties, with GF values up to 1.23, and sensitive and stable strain sensing properties. This work provides useful insights into the application of ion-specific effects to the field of hydrogels.

Neutrophil Granulopoiesis Optimized Through Ex Vivo Expansion of Hematopoietic Progenitors in Engineered 3D Gelatin Methacrylate Hydrogels.

Neutrophils are the first line of defense of the innate immune system. In response to methicillin-resistant Staphylococcus aureus infection in the skin, hematopoietic stem, and progenitor cells (HSPCs) traffic to wounds and undergo extramedullary granulopoiesis, producing neutrophils necessary to resolve the infection. This prompted the engineering of a gelatin methacrylate (GelMA) hydrogel that encapsulates HSPCs within a matrix amenable to subcutaneous delivery. The authors study the influence of hydrogel mechanical properties to produce an artificial niche for granulocyte-monocyte progenitors (GMPs) to efficiently expand into functional neutrophils that can populate infected tissue. Lin-cKIT+ HSPCs, harvested from fluorescent neutrophil reporter mice, are encapsulated in GelMA hydrogels of varying polymer concentration and UV-crosslinked to produce HSPC-laden gels of specific stiffness and mesh sizes. Softer 5% GelMA gels yield the most viable progenitors and effective cell-matrix interactions. Compared to suspension culture, 5% GelMA results in a twofold expansion of mature neutrophils that retain antimicrobial functions including degranulation, phagocytosis, and ROS production. When implanted dermally in C57BL/6J mice, luciferase-expressing neutrophils expanded in GelMA hydrogels are visualized at the site of implantation for over 5 days. They demonstrate the potential of GelMA hydrogels for delivering HSPCs directly to the site of skin infection to promote local granulopoiesis.

Accelerating the remodeling of collagen in cutaneous full-thickness wound using FIR soldering technology with bio-targeting nanocomposites hydrogel.

A novel composite wound dressing hydrogel by incorporating single-walled carbon nanotubes and indocyanine green into a dual-crosslinked hydrogel through Schiff base reaction was developed. The objective was to prevent wound infection and enhance the thermal effect induced by laser energy. The hydrogel matrix was constructed using oxidized gelatin, pre-crosslinked with calcium ions, along with carboxymethyl chitosan, crosslinked via Schiff base reaction. Optimization of the blank hydrogel's gelation time, swelling index, degradation rate, and mechanical properties was achieved by adding 0.1% SWCNT and 0.1% ICG. Among them, the SWCNT-loaded hydrogel BCG-SWCNT exhibited superior performance overall: a gelation time of 102 s; a swelling index above 30 after equilibrium swelling; a degradation rate of 100.5% on the seventh day; and a compressive modulus of 8.8 KPa. It displayed significant inhibition against methicillin-resistant Staphylococcus aureus infection in wounds. When combined with laser energy usage, the composite hydrogel demonstrated excellent pro-healing activity in rats.

Load-bearing columns inspired fabrication of ductile and mechanically enhanced BSA hydrogels

Currently, protein-based hydrogels are widely applied in soft materials, tissue engineering and implantable scaffolds owing to their excellent biocompatibility, and degradability. However, most protein-based hydrogels are soft brittle. In this study, a ductile and mechanically enhanced bovine serum albumin (BSA) hydrogel is fabricated by soaking the a 1-(3-dimethylaminopropyl)-3ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) induced BSA hydrogel in (NH4)2SO4 solution. An EDC/NHS coupling reaction induce protein coupling reactions that cause the BSA skeleton to resemble architectural load-bearing walls, protecting the integrity of the hydrogel and preventing collapse. The effects of the BSA and (NH4)2SO4 concentrations on the hydrogel mechanics are evaluated, and the possible strengthening mechanism is discussed. Besides, the highly kosmotropic ions greatly enhance the hydrophobic interaction within BSA gels and dehydration effect and their mechanical properties were significantly enhanced. The various mechanical properties of hydrogels can be regulated over a large window by soaking hydrogels into various ions. And most of them can be washed away, maintaining high biocompatibility of the protein. Importantly, the protein hydrogels prepared by this strategy could also be modified as strain sensors. In a word, this work demonstrates a new, universal method to provide multi-functional, biocompatible, strength enhanced and regulable mechanical pure protein hydrogel, combining the Hofmeister effect with -NH2/-COOH association groups.

Rational Design of Dynamically Super-Tough and Super-Stretchable Hydrogels for Deformable Energy Storage Devices.

Hydrogels possess unique polymer networks that offer flexibility/stretchability, high ionic conductivity, and resistance to electrolyte leakage, making them suitable for deformable energy storage devices. Endowing the mechanical functionality of the hydrogel electrolytes focus on either enhancing the stretchability or the toughness. However, the stretchability and the toughness are generally a trade-off that the stretchable gels are intrinsically prone to damage and sensitive to notches and cracks. Here, the regulating strategies on the hydrogel's mechanical properties are provided to develop the designated hydrogel electrolyte, where different polymeric network structures are constructed, including single network structures, semi-interpenetrating network structures, and interpenetrating dual-network structures. A comprehensive comparison of these polymer network structures is conducted to evaluate their mechanical stretchability and toughness. Designing super-tough and super-stretchable hydrogels based on specific application requirements can be realized by striking a balance by regulating the hydrogel structure. In specific, incorporating semi-interpenetrating networks significantly can enhance stretchability to achieve a break elongation up to 1300%, while the interpenetrating dual-networks can largely improve the toughness to realize the extraordinary fracture toughness of 6.843kJm-2. These findings offer valuable designing guidance for designated hydrogel electrolytes and the deformable zinc-silver battery is demonstrated with high mechanical stability and electrochemical performance.