Engineering nanocomposite hydrogels using dynamic bonds

A cutting-edge new framework for the pain management in children: nanotechnology

Pain is a subjective concept which is ever-present in the medical field. Health professionals are confronted with a variety of pain types and sources, as well as the challenge of managing a patient with acute or chronic suffering. An even bigger challenge is presented in the pediatric population, which often cannot quantify pain in a numerical scale like adults. Infants and small children especially show their discomfort through behavioral and physiological indicators, leaving the health provider with the task of rating the pain. Depending on the pathophysiology of it, pain can be classified as neuropathic or nociceptive, with the first being defined by an irregular signal processing in the nervous system and the second appearing in cases of direct tissue damage or prolonged contact with a certain stimulant. The approach is generally either pharmacological or non-pharmacological and it can vary from using NSAIDs, local anesthetics, opiates to physical and psychological routes. Unfortunately, some pathologies involve either intense or chronic pain that cannot be managed with traditional methods. Recent studies have involved nanoparticles with special characteristics such as small dimension and large surface area that can facilitate carrying treatments to tissues and even offer intrinsic analgesic properties. Pediatrics has benefited significantly from the application of nanotechnology, which has enabled the development of novel strategies for drug delivery, disease diagnosis, and tissue engineering. This narrative review aims to evaluate the role of nanotechnology in current pain therapy, with emphasis on pain in children.

Nanomaterial-integrated injectable hydrogels for craniofacial bone reconstruction

The complex anatomy and biology of craniofacial bones pose difficulties in their effective and precise reconstruction. Injectable hydrogels (IHs) with water-swollen networks are emerging as a shape-adaptive alternative for noninvasively rebuilding craniofacial bones. The advent of versatile nanomaterials (NMs) customizes IHs with strengthened mechanical properties and therapeutically favorable performance, presenting excellent contenders over traditional substitutes. Structurally, NM-reinforced IHs are energy dissipative and covalently crosslinked, providing the mechanics necessary to support craniofacial structures and physiological functions. Biofunctionally, incorporating unique NMs into IH expands a plethora of biological activities, including immunomodulatory, osteogenic, angiogenic, and antibacterial effects, further favoring controllable dynamic tissue regeneration. Mechanistically, NM-engineered IHs optimize the physical traits to direct cell responses, regulate intracellular signaling pathways, and control the release of biomolecules, collectively bestowing structure-induced features and multifunctionality. By encompassing state-of-the-art advances in NM-integrated IHs, this review offers a foundation for future clinical translation of craniofacial bone reconstruction.

Mechanochemistry: Fundamental Principles and Applications

Mechanochemistry is an emerging research field at the interface of physics, mechanics, materials science, and chemistry. Complementary to traditional activation methods in chemistry, such as heat, electricity, and light, mechanochemistry focuses on the activation of chemical reactions by directly or indirectly applying mechanical forces. It has evolved as a powerful tool for controlling chemical reactions in solid state systems, sensing and responding to stresses in polymer materials, regulating interfacial adhesions, and stimulating biological processes. By combining theoretical approaches, simulations and experimental techniques, researchers have gained intricate insights into the mechanisms underlying mechanochemistry. In this review, the physical chemistry principles underpinning mechanochemistry are elucidated and a comprehensive overview of recent significant achievements in the discovery of mechanically responsive chemical processes is provided, with a particular emphasis on their applications in materials science. Additionally, The perspectives and insights into potential future directions for this exciting research field are offered.

Dynamic hydrogel-metal-organic framework system promotes bone regeneration in periodontitis through controlled drug delivery

Periodontitis is a prevalent chronic inflammatory disease, which leads to gradual degradation of alveolar bone. The challenges persist in achieving effective alveolar bone repair due to the unique bacterial microenvironment's impact on immune responses. This study explores a novel approach utilizing Metal-Organic Frameworks (MOFs) (comprising magnesium and gallic acid) for promoting bone regeneration in periodontitis, which focuses on the physiological roles of magnesium ions in bone repair and gallic acid's antioxidant and immunomodulatory properties. However, the dynamic oral environment and irregular periodontal pockets pose challenges for sustained drug delivery. A smart responsive hydrogel system, integrating Carboxymethyl Chitosan (CMCS), Dextran (DEX) and 4-formylphenylboronic acid (4-FPBA) was designed to address this problem. The injectable self-healing hydrogel forms a dual-crosslinked network, incorporating the MOF and rendering its on-demand release sensitive to reactive oxygen species (ROS) levels and pH levels of periodontitis. We seek to analyze the hydrogel's synergistic effects with MOFs in antibacterial functions, immunomodulation and promotion of bone regeneration in periodontitis. In vivo and in vitro experiment validated the system's efficacy in inhibiting inflammation-related genes and proteins expression to foster periodontal bone regeneration. This dynamic hydrogel system with MOFs, shows promise as a potential therapeutic avenue for addressing the challenges in bone regeneration in periodontitis.

A Gas Therapy Strategy for Intestinal Flora Regulation and Colitis Treatment by Nanogel-Based Multistage NO Delivery Microcapsules

Current approaches to treating inflammatory bowel disease focus on the suppression of overactive immune responses, the removal of reactive intestinal oxygen species, and regulation of the intestinal flora. However, owing to the complex structure of the gastrointestinal tract and the influence of mucus, current small-molecule and biologic-based drugs for treating colitis cannot effectively act at the site of colon inflammation, and as a result, they tend to exhibit low efficacies and toxic side effects. In this study, nanogel-based multistage NO delivery microcapsules are developed to achieve NO release at the inflammation site by targeting the inflammatory tissues using the nanogel. Surprisingly, oral administration of the microcapsules suppresses the growth of pathogenic bacteria and increases the abundance of probiotic bacteria. Metabolomics further show that an increased abundance of intestinal probiotics promotes the production of metabolites, including short-chain fatty acids and indole derivatives, which modulate the intestinal immunity and restore the intestinal barrier via the interleukin-17 and PI3K-Akt signaling pathways. This work reveals that the developed gas therapy strategy based on multistage NO delivery microcapsules modulates the intestinal microbial balance, thereby reducing inflammation and promoting intestinal barrier repair, ultimately providing a new therapeutic approach for the clinical management of colitis.

Multifunctional tannic acid-based nanocomposite methacrylated silk fibroin hydrogel with the ability to scavenge reactive oxygen species and reduce inflammation for bone regeneration

The microenvironment of bone defect site is vital for bone regeneration. Severe bone defect is often accompanied with severe inflammation and elevated generation of reactive oxygen species (ROS) during bone repair. In recent years, the unfriendly local microenvironment has been paid more and more attention. Some bioactive materials with the ability to regulate the microenvironment to promote bone regeneration urgently need to be developed. Here, we develop a multifunctional composite hydrogel composed of photo-responsive methacrylate silk fibroin (SFMA), laponite (LAP) nanocomposite and tannic acid (TA), aiming to endow hydrogel with antioxidant, anti-inflammatory and osteogenic induction ability. Characterization results confirmed that the SFMA-LAP@TA hydrogel could significantly improve the mechanical properties of hydrogel. The ROS-Scavenging ability of the hydrogel enabled bone marrow mesenchymal stem cells (BMSCs) to survive against H2O2-induced oxidative stress. In addition, the SFMA-LAP@TA hydrogel effectively decreased the expression of pro-inflammatory factors in RAW264.7. More importantly, the SFMA-LAP@TA hydrogel could enhance the expression of osteogenic markers of BMSCs under inflammatory condition and greatly promote new bone formation in a critical-sized cranial defect model. Above all, the multifunctional hydrogel could effectively promote bone regeneration in vitro and in vivo by scavenging ROS and reducing inflammation, providing a prospective strategy for bone regeneration.

A nanocomposite hydrogel loaded with Ag nanoparticles reduced by aloe vera polysaccharides as an antimicrobial multifunctional sensor

Developing high-performance hydrogels with anti-freeze, and antimicrobial properties is crucial for the practical application of flexible sensors. In this study, we prepared silver nanoparticles (AgNPs) with aloe polysaccharide (AP) as a reducing agent. Then, the AP/AgNPs were added to a system of polyvinyl alcohol and borax crosslinked in water/glycerol to obtain a multifunctional conductive hydrogel. The incorporated AgNPs improved the conductivity (0.39 S/m) and mechanical properties (elongation at break: 732.9 %, fracture strength: 1267.6 kPa) of the hydrogel. In addition, resultant hydrogel exhibited potential for sensing strain, temperature, and humidity. When used as a strain sensor, the hydrogel system exhibited low detection limit (0.1 %), and fast response (0.08 s). The resistance of the hydrogel decreased with an increase in the absorbed moisture content, enabling humidity detection (25-95 %) to monitor breathing status. As a temperature sensor, the hydrogel supported a wide detection range (-50 to +90 °C) and sensitivity (-30-0 °C, temperature coefficient of resistance (TCR) = -5.64 %/°C) to detect changes in the ambient temperature. This study proposes a simple method for manufacturing multifunctional hydrogel sensors, which broadens their application prospects in wearable sensing and electronic products.

A nanoparticle reinforced microporous methacrylated silk fibroin hydrogel to promote bone regeneration

Natural polymer-based hydrogels have been widely applied in bone tissue engineering due to their excellent biocompatibility and outstanding ability of drug encapsulation. However, they have relatively weak mechanical properties and lack bioactivity. Hence, we developed a bioactive nanoparticle composite hydrogel by incorporating LAPONITE®, which is an osteo-inductive inorganic nanoparticle. The incorporation of the nanoparticle significantly enhanced its mechanical properties. In vitro evaluation indicated that the nanocomposite hydrogel could exhibit good biocompatibility. Besides, the nanocomposite hydrogel was proved to have excellent osteogenic ability with up-regulated expression of osteogenic markers such as type I collagen (COL-I), runt-related transcription factor-2 (Runx-2) and osteocalcin (OCN). Furthermore, the in vivo study confirmed that the composite nanocomposite hydrogel could significantly promote new bone formation, providing a prospective strategy for bone tissue regeneration.

Aldehyde group pendant-grafted pectin-based injectable hydrogel

Periodate oxidation has been the widely accepted route for obtaining aldehyde group-functionalized polysaccharides but significantly influenced the various physicochemical properties due to the ring opening of the backbone of polysaccharides. The present study, for the first time, presents a novel method for the preparation of aldehyde group-functionalized polysaccharides that could retain the ring structure and the consequent rigidity of the backbone. Pectin was collected as the representative of polysaccharides and modified with cyclopropyl formaldehyde to obtain pectin aldehyde (AP), which was further crosslinked by DL-lysine (LYS) via the Schiff base reaction to prepare injectable hydrogel. The feasibility of the functionalization was proved by FT-IR and 1H NMR techniques. The obtained hydrogel showed acceptable mechanical properties, self-healing ability, syringeability, and sustained-release performance. Also, as-prepared injectable hydrogel presented great biocompatibility with a cell proliferation rate of 96 %, and the drug-loaded hydrogel exhibited clear inhibition of cancer cell proliferation. Overall, the present study showed a new method for the preparation of aldehyde group-functionalized polysaccharides, and the drug-loaded hydrogel has potential in drug release applications.

Extracellular vesicle biopotentiated hydrogels for diabetic wound healing: The art of living nanomaterials combined with soft scaffolds

Diabetic wounds (DWs) pose a major challenge for the public health system owing to their high incidence, complex pathogenesis, and long recovery time; thus, there is an urgent need to develop innovative therapies to accelerate the healing process of diabetic wounds. As natural nanovesicles, extracellular vesicles (EVs) are rich in sources with low immunogenicity and abundant nutritive molecules and exert potent therapeutic effects on diabetic wound healing. To avoid the rapid removal of EVs, a suitable delivery system is required for their controlled release. Owing to the advantages of high porosity, good biocompatibility, and adjustable physical and chemical properties of hydrogels, EV biopotentiated hydrogels can aid in achieving precise and favorable therapy against diabetic wounds. This review highlights the different design strategies, therapeutic effects, and mechanisms of EV biopotentiated hydrogels. We also discussed the future challenges and opportunities of using EV biopotentiated hydrogels for diabetic wound healing.

Bioinspired self-healing injectable nanocomposite hydrogels based on oxidized dextran and gelatin for growth-factor-free bone regeneration

Hydrogels with great biocompatibility, biodegradability, and mechanical properties, combined with osteoconductivity, osteoinductivity, and osteointegration as biomaterials for bone regeneration without adding exogenous growth factors and cells are highly appealing but challenging. Here, inspired by organic-inorganic analogues of natural bone tissue and the adhesion chemistry of mussels, nanocomposite hydrogels with self-healing, injectable, adhesive, antioxidant, and osteoinductive properties (termed GO-PHA-CPs) were constructed by Schiff base cross-linking between dopamine-modified gelatin (Gel-DA) and oxidized dextran (ODex). Furthermore, the hydrogel network was enhanced by the introduction of polydopamine-functionalized nanohydroxyapatite (PHA) by improving the interfacial compatibility between the rigid inorganic particles and the flexible hydrogel matrix. Bioactive cod peptides (CPs) with osteogenic activity from Atlantic cod were further incorporated into the nanocomposite hydrogel. As a result, the multicomponent nanocomposite hydrogel favored the adhesion and spreading of MC3T3-E1 cells. The increased ALP activity suggested that GO-PHA-CPs hydrogels contributed to the osteogenic differentiation of MC3T3-E1 cells. The suitability of GO-PHA-CPs hydrogels for enhancing bone regeneration in vivo was further confirmed by the rat femoral defect model. Our results indicate that the multifunctional GO-PHA-CPs nanocomposite hydrogels without growth factors are a promising and effective candidate material for bone regeneration.

Cartilage-inspired terpolymer hydrogel with excellent mechanical properties and superior lubricating ability

Osteoarthritis (OA), the most common degenerative joint disorder, seriously affects patients' daily activities. Recently, hydrogels, due to their similar structure to articular cartilage, have shown great potential as cartilage-repairing materials. In the present work, we developed a simple process for fabricating terpolymer [P(acrylamide-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/Fe3+] hydrogel [P(AAm-co-AAc-co-AMPS)/Fe3+]. The content of AMPS was found to show a crucial effect on the mechanical and tribological performance of the terpolymer hydrogel. When the content of AMPS was 0.45 mol L-1, the compressive strength, modulus, and friction coefficient of the terpolymer hydrogel were 66.60 ± 1.79 MPa, 2.10 ± 0.16 MPa, and 0.032, respectively. In addition, the hydrogel showed high wear durability and the friction coefficient was as low as 0.038 after 3.6 × 105 sliding cycles.

Reversible Molecular Capture and Release in Microfluidics by Host-Guest Interactions in Hydrogel Microdots

The integration of microscopic hydrogels with high specific surface area and physically reactive groups into microfluidic systems for selective molecular interactions is attracting increasing attention. Herein, the reversible capture and release of molecules through host-guest interactions of hydrogel dots in a microfluidic device is reported, which translates the supramolecular chemistry to the microscale conditions under continuous flow. Polyacrylamide (PAAm) hydrogel arrays with grafted β-cyclodextrin (β-CD)  modified poly(2-methyl-2-oxazoline) (CD-PMOXA) chains are fabricated by photopolymerization and integrated into a polydimethylsiloxane (PDMS)-on-glass chip. The β-CD/adamantane (β-CD/Ada) host-guest complex is confirmed by two dimensional Nuclear Overhauser Effect Spectroscopy NMR (2D NOESY NMR) prior to transfer to microfluidics. Ada-modified molecules are successfully captured by host-guest interaction formed between the CD-PMOXA grafted chains in the hydrogel network and the guest molecule in the solution. Furthermore, the captured molecules are released by perfusing free β-CD with higher binding affinity than those grafted in the hydrogel array. A small guest molecule adamantane-fluorescein-isothiocyanate (Ada-FITC) and a macromolecular guest molecule (Ada-PMOXA-Cyanine 5 (Cy5)) are separately captured and released for three times with a release ratio up to 46% and 92%, respectively. The reproducible capture and release of functional molecules with different sizes demonstrates the stability of this hydrogel system in microfluidics and will provide an opportunity for future applications.

Synthesis, Characterization, Properties, and Biomedical Application of Chitosan-Based Hydrogels

The prospective applications of chitosan-based hydrogels (CBHs), a category of biocompatible and biodegradable materials, in biomedical disciplines such as tissue engineering, wound healing, drug delivery, and biosensing have garnered great interest. The synthesis and characterization processes used to create CBHs play a significant role in determining their characteristics and effectiveness. The qualities of CBHs might be greatly influenced by tailoring the manufacturing method to get certain traits, including porosity, swelling, mechanical strength, and bioactivity. Additionally, characterization methods aid in gaining access to the microstructures and properties of CBHs. Herein, this review provides a comprehensive assessment of the state-of-the-art with a focus on the affiliation between particular properties and domains in biomedicine. Moreover, this review highlights the beneficial properties and wide application of stimuli-responsive CBHs. The main obstacles and prospects for the future of CBH development for biomedical applications are also covered in this review.

Self-Healing, Reconfigurable, Thermal-Switching, Transformative Electronics for Health Monitoring

Soft, deformable electronic devices provide the means to monitor physiological information and health conditions for disease diagnostics. However, their practical utility is limited due to the lack of intrinsical thermal switching for mechanically transformative adaptability and self-healing capability against mechanical damages. Here, the design concepts, materials and physics, manufacturing approaches, and application opportunities of self-healing, reconfigurable, thermal-switching device platforms based on hyperbranched polymers and biphasic liquid metal are reported. The former provides excellent self-healing performance and unique tunable stiffness and adhesion regulated by temperature for the on-skin switch, whereas the latter results in liquid metal circuits with extreme stretchability (>900%) and high conductivity (3.40 × 104  S cm-1 ), as well as simple recycling capability. Triggered by the increased temperature from the skin surface, a multifunctional device platform can conveniently conform and strongly adhere to the hierarchically textured skin surface for non-invasive, continuous, comfortable health monitoring. Additionally, the self-healing and adhesive characteristics allow multiple multifunctional circuit components to assemble and completely wrap on 3D curvilinear surfaces. Together, the design, manufacturing, and proof-of-concept demonstration of the self-healing, transformative, and self-assembled electronics open up new opportunities for robust soft deformable devices, smart robotics, prosthetics, and Internet-of-Things, and human-machine interfaces on irregular surfaces.

Synthesis and Processing of Dynamic Covalently Crosslinked Polydextran/Carbon Dot Nanocomposite Hydrogels with Tailorable Microstructures and Properties

Using functionalized nanoparticles to crosslink hydrophilic polymers is a growing theme of directly constructing nanocomposite (NC) hydrogels. Employing dynamic covalent chemistry at the nanoparticle-polymer interface is particularly attractive due to the spontaneous formation and reversible manner of dynamic covalent bonds. However, the structure and property modulation of the dynamic covalently crosslinked NC hydrogels has not been thoroughly discussed. Here, we fabricated NC hydrogels by using amine-functionalized carbon dots (CDs) to crosslink polydextran aldehyde (PDA) polymers through imine bond formation. The role of PDA with different oxidation degrees (i.e., PDA10, PDA30, and PDA50) in affecting the microstructures and properties of PDA@CD hydrogels was systematically investigated, showing that the PDA50@CD hydrogel presented the densest structure and the highest mechanical strength among the three PDA@CD hydrogels. The pH-responsiveness, 3D printing, electrospinning, and biocompatibility of PDA@CD hydrogels were also demonstrated, showing the great promise of using PDA@CD hydrogels for applications in biomedicine and biofabrication.

Toward Tissue-Like Material Properties: Inducing In Situ Adaptive Behavior in Fibrous Hydrogels

The materials properties of biological tissues are unique. Nature is able to spatially and temporally manipulate (mechanical) properties while maintaining responsiveness toward a variety of cues; all without majorly changing the material's composition. Artificial mimics, synthetic or biomaterial-based are far less advanced and poorly reproduce the natural cell microenvironment. A viable strategy to generate materials with advanced properties combines different materials into nanocomposites. This work describes nanocomposites of a synthetic fibrous hydrogel, based on polyisocyanide (PIC), that is noncovalently linked to a responsive cross-linker. The introduction of the cross-linker transforms the PIC gel from a static fibrous extracellular matrix mimic to a highly dynamic material that maintains biocompatibility, as demonstrated by in situ modification of the (non)linear mechanical properties and efficient self-healing properties. Key in the material design is cross-linking at the fibrillar level using nanoparticles, which, simultaneously may be used to introduce more advanced properties.

Responsive Hydrogels Based on Triggered Click Reactions for Liver Cancer

Globally, liver cancer, which is one of the major cancers worldwide, has attracted the growing attention of technological researchers for its high mortality and limited treatment options. Hydrogels are soft 3D network materials containing a large number of hydrophilic monomers. By adding moieties such as nitrobenzyl groups to the network structure of a cross-linked nanocomposite hydrogel, the click reaction improves drug-release efficiency in vivo, which improves the survival rate and prolongs the survival time of liver cancer patients. The application of a nanocomposite hydrogel drug delivery system can not only enrich the drug concentration at the tumor site for a long time but also effectively prevents the distant metastasis of residual tumor cells. At present, a large number of researches have been working toward the construction of responsive nanocomposite hydrogel drug delivery systems, but there are few comprehensive articles to systematically summarize these discoveries. Here, this systematic review summarizes the synthesis methods and related applications of nanocomposite responsive hydrogels with actions to external or internal physiological stimuli. With different physical or chemical stimuli, the structural unit rearrangement and the controlled release of drugs can be used for responsive drug delivery in different states.

Protocatechuic Acid-Based Supramolecular Hydrogel Targets SerpinB9 to Achieve Local Chemotherapy for OSCC

Protocatechuic acid (PCA) is a natural phenolic acid present in daily vegetables and fruits. Notably, PCA was demonstrated to inhibit the biological function of SerpinB9 (Sb9) and exhibit an excellent antitumor effect, showing great potential in cancer treatment. However, the short half-life time limits PCA's wide application against cancers. To overcome this shortage of PCA, we integrated PCA and another natural product with strong self-assembling properties, isoguanosine (isoG), to develop a novel multifunctional supramolecular hydrogel with good biocompatibility and injectability, which remarkably lengthens the releasing time of PCA and exerts considerable anticancer effects in vitro and in vivo. Besides, we surprisingly found that PCA could not only target Sb9 but also restrain cancer development through activating the JNK/P38 pathway, decreasing the ROS level, and repairing cancer stemness. In all, our results demonstrate that this PCA-based hydrogel could act as a multifunctional hydrogel system equipped with considerable anticancer effects, providing potential local administration integrating with targeted therapy and chemotherapy in one simple modality.

Self-Healing Hyaluronic Acid Nanocomposite Hydrogels with Platelet-Rich Plasma Impregnated for Skin Regeneration

The development of natural hydrogels with sufficient strength and self-healing capacity to accelerate skin wound healing is still challenging. Herein, a hyaluronic acid nanocomposite hydrogel was developed based on aldehyde-modified sodium hyaluronate (AHA), hydrazide-modified sodium hyaluronate (ADA), and aldehyde-modified cellulose nanocrystals (oxi-CNC). This hydrogel was formed in situ using dynamic acylhydrazone bonds via a double-barreled syringe. This hydrogel exhibited improved strength and excellent self-healing ability. Furthermore, platelet-rich plasma (PRP) can be loaded in the hyaluronic acid nanocomposite hydrogels (ADAC) via imine bonds formed between amino groups on PRP (e.g., fibrinogen) and aldehyde groups on AHA or oxi-CNC to promote skin wound healing synergistically. As expected, ADAC hydrogel could protect and release PRP sustainably. In animal experiments, ADAC@PRP hydrogel significantly promoted full-thickness skin wound healing through enhancing the formation of granulation tissue, facilitating collagen deposition, and accelerating re-epithelialization and neovascularization. This self-healing nanocomposite hydrogel with PRP loading appears to be a promising candidate for wound therapy.

Preparation of a "Branch-Fruit" structure chitosan nanofiber physical hydrogels with high mechanical strength and pH-responsive controlled drug release properties

The poor mechanical properties of chitosan physical hydrogels seriously hinder their application in the biomedical field. Inspired by the structure of cell tissues, a novel chitosan nanofiber (CSNF)/Hyaluronic acid (HA)/β-glycerophosphate disodium (β-GP) drug-loaded hydrogel was prepared by micro-dissolution and physical crosslinking. The hydrogel has a “Branch-Fruit” structure and exhibits excellent mechanical properties, good biocompatibility and cell-adhesion properties. Human cancer cells (HeLa) can adhere to the hydrogel surface, which might facilitate tumor site-specific administration of drugs. This material also exhibits high pH sensitivity, with which drug release can be triggered under acidic conditions at pH 4.00. The mechanical strength and drug release behavior of this hydrogel can be easily adjusted by varying the CSNF content.

Representation of the gelation mechanism of CSNF/HA/β-GP precursor solution.

An UV-photo and ionic dual responsive interpenetrating network hydrogel with shape memory and self-healing properties

Shape memory hydrogels have attracted extensive attention in fields such as artificial tissues, biomimetic devices and diagnostics, and intelligent biosensors. However, the practical applications were hindered by the absence of self-healing capability and multi-stimuli-responsiveness. To address these issues, we developed a shape memory hydrogel with self-healing and dual stimuli-response performance. The hydrogel system was constructed via an interpenetrating network consisting of in situ radical polymerization and host-guest interaction. The hydrogel exhibited rapid self-healing property, which can be stretched after self-healing for 1 min at 25 °C. Besides, the hydrogel displayed varied swelling performance in different light or solvent conditions. Moreover, the hydrogel showed a dual stimuli-responsive shape memory effect to ultraviolet (UV) light and ionic strength in 1 min. Such a shape memory hydrogel with self-healing ability and multi-stimuli-responsive properties will offer an option toward intelligent soft materials for biomedical and bionic research.

DNA-Based Daisy Chain Rotaxane Nanocomposite Hydrogels as Dual-Programmable Dynamic Scaffolds for Stem Cell Adhesion

Interlocked DNA nanostructures perform programmable movements in nanoscales such as sliding, contraction, and expansion. However, utilizing nanoscaled interlocked movements to regulate the functions of larger length scaled matrix and developing their applications has not yet been reported. Herein we describe the assembly of DNA-based daisy chain rotaxane nanostructure (DNA-DCR) composed of two hollow DNA nanostructures as macrocycles, two interlocked axles and two triangular prism-shaped DNA structures as stoppers, in which three mechanical states─fixed extended state (FES), sliding state (SS), and fixed contracted state (FCS)─are characterized by using toehold-mediated strand displacement reaction (SDR). The DNA-DCRs are further used as nanocomposites and introduced into hydrogel matrix to produce interlocked hydrogels, which shows modulable stiffness by elongating the interlocked axles to regulate the hydrogel swelling with hybridization chain reaction (HCR) treatment. Then the DCR-hydrogels are employed as dynamic biointerfaces for human mesenchymal stem cells (hMSCs) adhesion studies. First, hMSCs showed lower cell density on bare DCR-hydrogel treated with HCR-initiated swelling for stiffness decreasing. Second, the cell adhesion ligand (RGD) modified DNA-DCRs are constructed for hydrogel functionalization. DCR^(RGD) hydrogel endows the mobility of RGDs by switching the mechanical states of DNA-DCR. HMSCs showed increased cell density on DCR^SS(RGD) hydrogel than on DCR^FCS(RGD) hydrogel. Therefore, our DNA-DCR nanocomposite hydrogel exhibit dual-programmable performances including swelling adjustment and offering sliding for incorporated ligands, which can be both utilized as dynamic scaffolds for regulating the stem cell adhesion. The dual-programmable cross-scale regulation from interlocked DNA nanostructures to hydrogel matrix was achieved, demonstrating a new pathway of DNA-based materials.

Recent Advances in Design Strategies of Tough Hydrogels

Hydrogels are a fascinating class of materials popular in numerous fields, including tissue engineering, drug delivery, soft robotics, and sensors, attributed to their 3D network porous structure containing a significant amount of water. However, traditional hydrogels exhibit poor mechanical strength, limiting their practical applications. Thus, many researchers have focused on the development of mechanically enhanced hydrogels. This review describes the design considerations for constructing tough hydrogels and some of the latest strategies in recent years. These tough hydrogels have an up-and-coming prospect and bring great hope to the fields of biomedicine and others. Nonetheless, it is still no small challenge to realize hydrogel materials that are tough, multifunctional, intelligent, and zero-defect. This article is protected by copyright. All rights reserved.

Dynamic covalent hydrogel of natural product baicalin with antibacterial activities

Baicalin has been demonstrated to have multiple pharmacological activities but low solubility. Various baicalin hydrogels have been used to improve its solubility and break its limitation in clinical applications. However, traditional baicalin hydrogels contain numerous ingredients and usually show low baicalin loading capacity. Herein, we discovered a dynamic covalent hydrogel only consisting of baicalin and inorganic borate, in which baicalin is considered as the carrier and drug without other ingredients. The dynamic boronate bonds endow the hydrogel with excellent degradability and multi-stimuli-responsiveness. Moreover, the hydrogel displayed remarkable thixotropy, moldability, and self-healing properties. And the biocompatible baicalin hydrogel exhibited significant antibacterial activities, and can be considered as a potential drug delivery system for biomedical applications.

Nanostructured Lipid Carriers-Hydrogels System for Drug Delivery: Nanohybrid Technology Perspective

Advanced hybrid component development in nanotechnology provides superior functionality in the application of scientific knowledge for the drug delivery industry. The purpose of this paper is to review important nanohybrid perspectives in drug delivery between nanostructured lipid carriers (NLC) and hydrogel systems. The hybrid system may result in the enhancement of each component's synergistic properties in the mechanical strength of the hydrogel and concomitantly decrease aggregation of the NLC. The significant progress in nanostructured lipid carriers-hydrogels is reviewed here, with an emphasis on their preparation, potential applications, advantages, and underlying issues associated with these exciting materials.

Fabrication of Multiresponsive Magnetic Nanocomposite Double-Network Hydrogels for Controlled Release Applications

Nanocomposite double-network hydrogels (ncDN hydrogels) have been demonstrated as promising biomaterials to present several desired properties (e.g., high mechanical strength, stimuli-responsiveness, and local therapy) for biomedicine. Here, a new type of ncDN hydrogels featuring definable microstructures and properties as well as multistimuli responsiveness for controlled release applications is developed. Amine-functionalized iron oxide nanoparticles (IOPs_NH₂ ) are used as nanoparticle cross-linkers to simultaneously connect the dual networks of gelatin (Gel) and polydextran aldehyde (PDA) through hydrogen bonding, electrostatic interactions, and dynamic imine bonds. The pH- and temperature-responsive Gel/PDA/IOP_NH₂ ncDN hydrogels present a fast release profile of proteins at acidic pH and high temperature. Besides, IOP_NH₂ also contributes the magnetic-responsiveness to the ncDN hydrogels, allowing the use of magnetic field to generate heat to facilitate the structural change of hydrogels and the subsequent applications. Taken together, a versatile ncDN hydrogel platform capable of multistimuli responsiveness and local heating for controlled release is developed for advanced biomedical applications.

Hydrogel Preparation Methods and Biomaterials for Wound Dressing

Wounds have become one of the causes of death worldwide. The metabolic disorder of the wound microenvironment can lead to a series of serious symptoms, especially chronic wounds that bring great pain to patients, and there is currently no effective and widely used wound dressing. Therefore, it is important to develop new multifunctional wound dressings. Hydrogel is an ideal dressing candidate because of its 3D structure, good permeability, excellent biocompatibility, and ability to provide a moist environment for wound repair, which overcomes the shortcomings of traditional dressings. This article first briefly introduces the skin wound healing process, then the preparation methods of hydrogel dressings and the characteristics of hydrogel wound dressings made of natural biomaterials and synthetic materials are introduced. Finally, the development prospects and challenges of hydrogel wound dressings are discussed.

Hyaluronic Acid Hydrogels Crosslinked in Physiological Conditions: Synthesis and Biomedical Applications

Hyaluronic acid (HA) hydrogels display a wide variety of biomedical applications ranging from tissue engineering to drug vehiculization and controlled release. To date, most of the commercially available hyaluronic acid hydrogel formulations are produced under conditions that are not compatible with physiological ones. This review compiles the currently used approaches for the development of hyaluronic acid hydrogels under physiological/mild conditions. These methods include dynamic covalent processes such as boronic ester and Schiff-base formation and click chemistry mediated reactions such as thiol chemistry processes, azide-alkyne, or Diels Alder cycloaddition. Thermoreversible gelation of HA hydrogels at physiological temperature is also discussed. Finally, the most outstanding biomedical applications are indicated for each of the HA hydrogel generation approaches.