Self-healing Composite Hydrogels Research Articles

Cu2O-SnO2-PDA heterozygous nanozyme doped hydrogel mediated conglutinant microenvironment regulation for wound healing therapy

Bacterial infection significantly hinders the wound healing process. Overuse of antibiotics has led to the rise of drug resistance in bacteria, making the development of smart medical dressings that promote wound healing without antibiotics, a critical need. In this study, Cu₂O-SnO₂-PDA (PCS) nanoenzymes with Fenton-like activity and high photothermal conversion efficiency were developed. These nanoenzymes were then incorporated into a hydrogel through cross-linking of acrylamide (AM) and N-[Tris-(hydroxymethyl)methyl] acrylamide (THMA), forming a tough, highly-adhesive, and self-healing composite hydrogel (AT/PCS) with antimicrobial properties. The AT/PCS hydrogel exhibits excellent mechanical strength and adhesion, facilitating increased oxygen levels and strong adherence to the wound site. Moreover, it effectively regulates the wound microenvironment by combining synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT) for antibacterial treatment. The AT/PCS hydrogel enhances collagen deposition and expedites wound healing in a rat model, largely due to its potent antibacterial properties.

Fish Gelatin-Based Flexible and Self-Healing Hydrogel Modified by Fe2(SO4)3.

The application of fish gelatin (FG) is limited due to its poor mechanical properties and thermal stability, both of which could be significantly improved by gellan gum (GG) found in previous research. However, the FG/GG composite hydrogel was brittle and easily damaged by external forces. It was found that the composite hydrogel with Fe2(SO4)3 showed good flexibility and self-healing properties in the pre-experiment. Thus, the synergistic effect of FG, GG and Fe2(SO4)3 on the mechanical properties of the composite hydrogel was investigated in this study. According to one-way experiments, response surface tests and Texture Profile Analysis, it was found that under the optimum condition of FG concentration 186.443 g/L, GG concentration 8.666 g/L and Fe2(SO4)3 concentration 56.503 g/L, the springiness of the composite cylindrical hydrogel with the height of 25 mm formed in 25 mL beakers (bottom diameter 30 mm) was 7.602 mm. Determination of the rheological properties, compression performance, adhesive performance and self-healing properties showed that the composite hydrogel had good thermal stability, flexibility and self-healing properties with good adhesion, skin compliance and compressive strength, and it was easy to remove. The composite hydrogel showed strong antimicrobial activity against A. salmonicida and V. parahaemolyticus. All hydrogels showed a uniform and porous structure. The 3D structure of the composite hydrogel was much looser and more porous than the pure FG hydrogel. The flexible and self-healing composite hydrogel with some antimicrobial activity is suitable for the development of medical dressings, which broadens the applications of the composite hydrogel.

Facile preparation of self-healing hydrogels based on chitosan and PVA with the incorporation of curcumin-loaded micelles for wound dressings

The increased demand for improved strategies for wound healing has, in recent years, motivated the development of multifunctional hydrogels with favorable bio-compatibility and antibacterial properties. To this regard, the current study presented the design of a novel self-healing composite hydrogel that could perform as wound dressing for the promotion of wound healing. The composite hydrogels were composed of polyvinyl alcohol (PVA), borax and chitosan functionalized with sialic acid (SA-CS) and curcumin loaded pluronic F127 micelles. The hydrogels were formed through the boronic ester bond formation between PVA, SA-CS and borax under physiological conditions and demonstrated adjustable mechanical properties, gelation kinetics and antibacterial properties. When incubating with NIH3T3 cells, the hydrogels also demonstrated good biocompatibility. These aspects offer a promising foundation for their prospective applications in developing clinical materials for wound healing.

MoS2-functionalized chitosan hydrogel with antibacterial and antioxidant functions promotes healing of infected diabetic wounds

Construction and application of a MoS2-based injectable self-healing composite hydrogel with antibacterial and antioxidant dual functions for promoting infected diabetic wound healing.

An extracellular matrix-inspired self-healing composite hydrogel for enhanced platelet-rich plasma-mediated chronic diabetic wound treatment

Diabetes is generally accompanied by difficult-to-heal wounds, which often lead to permanent disability and even death of patients. Because of the abundance of a variety of growth factors, platelet rich plasma (PRP) has been proven to have great clinical potential for diabetic wound treatment. However, how to suppress the explosive release of its active components while realizing adaptability to different wounds remains important for PRP therapy. Here, an injectable, self-healing, and non-specific tissue-adhesive hydrogel formed by oxidized chondroitin sulfate and carboxymethyl chitosan was designed as an encapsulation and delivery platform for PRP. With a dynamic cross-linking structural design, the hydrogel can meet the clinical demands of irregular wounds with controllable gelation and viscoelasticity. Inhibition of PRP enzymolysis as well as sustained release of its growth factors is realized with the hydrogel, enhancing cell proliferation and migration in vitro. Notably, greatly accelerated healing of full thickness wounds of diabetic skins is enabled by promoting the formation of granulation tissues, collagen deposition and angiogenesis as well as reducing inflammation in vivo. This self-healing and extracellular matrix-mimicking hydrogel provides powerful assistance to PRP therapy, enabling its promising applications for the repair and regeneration of diabetic wounds.

Dual Crosslinked-Network Self-Healing Composite Hydrogels Exhibit Enhanced Water Adaptivity and Reinforcement

Despite the self-healing and mechanical stimuli and responsive merits of wearable hydrogel devices, achieving efficient strategies to improve their properties (i.e., mechanical strength and water adaptivity) remains challenging. Hydrogels with multinetwork structures usually display exceptional high mechanical strength via their unique macromolecular hierarchical structure comprising two or more interlaced networks. Herein, we exploit polyol/borax systems to design self-healing bicomponent polymer network hydrogels composed of polyvinyl alcohol (PVA) and guar. Our results have shown that due to the formation of bicomponent network structures, considerable reinforcement in the storage modulus and viscoelastic behaviors is achieved. Such improvements are accompanied by enhanced water resistance, which is in sharp contrast to the water-soluble nature of the PVA hydrogel. Moreover, the fabricated composite hydrogel well keeps the self-healing and mechanical stimulus-responsive merits and does not cause a decrease in thermal stability.

An injectable, self-healing composite hydrogel with enhanced near-infrared photo-antibacterial therapeutic effects for accelerated wound healing

Antibacterial hydrogels with injectable and self-healing properties have attracted much attention in the field of wound dressings because they not only can prevent bacterial infections, but also meet the basic needs for wound healing. However, how to achieve high antibacterial efficacy and low drug resistance for hydrogels is still a challenge. Herein, an injectable, self-healing, near-infrared (NIR) photosensitive antibacterial hydrogel composed of CuS-grafted-curcumin (CuS@C) and carboxymethyl cellulose modified with aldehyde groups and hydroxypropyl trimethyl ammonium chloride chitosan is prepared for wound dressings. The p-n junction formed between curcumin and CuS promotes separation of electron-hole pairs, enhances the mobility of photogenerated charges, and destroys the conjugated structure of curcumin simultaneously consequently increasing the photocatalytic activity. CuS@C is immobilized and distributed uniformly in the hydrogel via the π-π conjugation ring. The hybrid hydrogel exhibits excellent antibacterial activity after irradiation with 808 NIR light for 10 min due to the enhanced photodynamic and photothermal antibacterial effects. In addition, the hybrid structure improves the biocompatibility of CuS and expedites infected-wound healing at a mild temperature of 45 ℃. This organic/inorganic hybrid is shown to be an excellent wound dressing for the treatment of bacterial-infected wounds.

Injectable, Adhesive, and Self-Healing Composite Hydrogels Loaded With Oxybutynin Hydrochloride for the Treatment of Overactive Bladder in Rats.

Object: The aim of this study was to prepare injectable, adhesive, and self-healing composite hydrogels loaded with oxybutynin hydrochloride and verify its function in the treatment of overactive bladder. Method: The ultraviolet (UV) absorption of oxybutynin (Oxy) in the solution was detected using a UV spectrophotometer at 233 nm, and the cumulative drug release was calculated using Origin software. L929 mouse fibroblasts were used to test cell adhesion to OCP50 and OCP100 hydrogels. Both FT-IR and NMR overactive bladder demonstrated that Dex was oxidized to PDA with aldehyde groups. Urodynamic examinations were performed 24 h after intraperitoneal injection in the rat model. The relative expression levels of Orai1 and STIM1 were detected by western blot (WB) and QPCR. Results: After loading Oxy, the shear adhesion under the wet conditions of OCP50 and OCP100 was higher than CP50 and CP100 (p < 0.05), and both were suitable for intravaginal administration. After 72 h of release, oxybutynin released 82.8% in OCP100 hydrogel and 70% in OCP50. Compared to the model, OCP50, CP100, and OCP100 relieved the overactive bladder and inhibited the expression of Orail and STIM1. Conclusions: Oxybutynin hydrogel could provide relief to overactive bladder by decreasing the expression of Orail and STIM1 in rats.

An anti-freezing wearable strain sensor based on nanoarchitectonics with a highly stretchable, tough, anti-fatigue and fast self-healing composite hydrogel

The application of conductive hydrogel sensors in wearable devices and electronic skin has aroused great research interest. However, hydrogel sensor cannot simultaneously have good self-healing properties, anti-freezing properties and excellent anti-fatigue properties, which results in poor reusability and unstable sensing performance. A composite hydrogel was synthesized by one-pot method using polyvinyl alcohol, acrylamide, sodium alginate and glycerol as raw materials. The obtained hydrogel has excellent mechanical properties (0.51 MPa stress, 1500% elongation at break and tensile toughness of 3.6 MJ/m3) and fast self-healing performance with healing efficiency (HE) as high as 92% without any external stimulus. At the same time, glycerol has strong freeze resistance for hydrogels. The hydrogel can stably transmit electrical signals at subzero temperature (−20 °C). In addition, we also verified that the hydrogel could self-recover in a short time through cyclic stretching, indicating the fatigue resistance and rapid recovery of the material.

Graphene-based hydrogel with embedded gold nanoparticles as a recyclable catalyst for the degradation of 4-nitrophenol

Hydrogels have been utilized as a sort of scaffold in catalytic field since they can offer good accommodation for noble metal nanoparticles (NPs) to the preparation of recyclable catalysts. In this work, the poly(4-vinylpyridine) (P4VP) grafted graphene oxide (GO) was firstly synthesized through surface-initiated atom transfer radical polymerization (SI−ATRP). Then, a tough and self-healable composite hydrogel was fabricated by integration of the P4VP-grafted GO into poly(acrylic acid) (PAA) matrix through hierarchically hydrogen-bonding interactions and simultaneous in-situ growth of gold nanoparticles (AuNPs) in the hydrogel scaffold. The as-prepared AuNPs@GO-g-P4VP/PAA composite hydrogel possesses improved mechanical strength and integrity, and exhibits higher catalytic activity in the reductive degradation of 4-nitrophenol into 4-aminophenol than other reported AuNPs-loaded hydrogel catalysts. In addition, the self-healing composite hydrogel catalyst shows ease of separation as well as good reusability without obvious loss of catalytic activity. This work provides an attractive method for the synthesis of robust functional nanoparticle-embedded composite hydrogel for application in various fields.

An Injectable, Self-Healing Composite Hydrogel with Enhanced Near-Infrared Photo-Antibacterial Therapeutic Effects for Accelerated Wound Healing

An Injectable, Self-Healing Composite Hydrogel with Enhanced Near-Infrared Photo-Antibacterial Therapeutic Effects for Accelerated Wound Healing

Polypyrrole-Doped Conductive Self-Healing Composite Hydrogels with High Toughness and Stretchability.

In recent years, hydrogels with self-healing capability and conductivity have become ideal materials for the design of electrodes, soft robotics, electronic skin, and flexible wearable devices. However, it is still a critical challenge to achieve the synergistic characteristics of high conductivity, excellent self-healing efficiency without any stimulations, and decent mechanical properties. Herein, we developed a ferric-ion (Fe3+) crosslinked acrylic acid and chitosan polymer hydrogel using embedded polypyrrole particles with features of high conductivity (2.61S·m-1) and good mechanical performances (a tensile strength of 628%, a stress of 0.33 MPa, an elastic modulus of 0.146 MPa, and a toughness of 1.14 MJ·m-3). In addition, the self-healing efficiency achieved 93% in tensile strength after healing in the air for 9 h without any external stimuli. Therefore, with these outstanding mechanical, self-healing, and conductive abilities all in one, it is possible to fabricate a new kind of soft material with wide applications.

An injectable, self-healing hydrogel system from oxidized pectin/chitosan/γ-Fe2O3

Injectable hydrogels with self-healing ability present great potential for drug delivery. They could be facilely implanted in vivo and maintained structural and functional integrity till the hydrogel arriving at target sites. Herein, a series of injectable and self-healing composite hydrogel were developed as delivery vehicles for anti-cancer drug. The hydrogels were obtained with varying ratios of oxidized pectin/chitosan to nano γ-Fe2O3, which present excellent injectable, self-healing, magnetic, high biocompatible, and anti-cancer properties. The nano γ-Fe2O3 with particle size of about 0.25 μm loaded on the surface of hydrogel. Magnetic hysteresis loops of the hydrogel presented S-shape over the applied magnetics and the MS value was 4.86 emu/g. When pH dropped from 7.4 to 6.5 or temperature increased form 36 °C to 37 °C, the percentage increase in the swelling rate of OP4-400 reached to 35.89% and 25.13%, respectively. The composite hydrogels could continuously release water-soluble 5-FU for more than 12 h. In addition, the drug delivery systems indicated acceptable anti-cancer property though trace amounts of 5-FU were added in the hydrogel systems. The addition of γ-Fe2O3 could not only be beneficial to the targeting but also collectively enhance the anti-cancer property.

Highly Stretchable, Compressible, Adhesive, Conductive Self-healing Composite Hydrogels with Sensor Capacity

The design and fabrication of conductive hydrogels with high stretchability, compressibility, self-healing properties and good adhesion remains a significant challenge. We have fabricated composite hydrogels by random polymerization of acrylic acid (AA) and dopamine (DA) in the presence of multi-walled carbon nanotubes (MWCNTs). The π-π interaction between DA and MWCNTs makes MWCNTs stably and homogenously dispersed in water. The fabricated PAA-PDA/CNT composite hydrogels possess relatively high mechanical strength (maximum Young’s modulus: 800 kPa) and can be stretched to 1280% strain and compressed to 80% strain. The multiple hydrogen bonding formed between functional groups of PAA-PDA and MWCNTs can effectively dissipate energy and quickly achieve self-healing. The composite hydrogels also show good adhesion and can easily adhere to various inorganic or organic surfaces. In addition, the hydrogel reveals stable strain sensitivity and can be used as skin sensors.

Self-healing composite hydrogel with antibacterial and reversible restorability conductive properties.

Self-healable PAA/PPy–Fe composite hydrogels have been simply synthesized in one step and utilized for antibacterial and electrical conductivity application. The network of hydrogel is composed of polyacrylic acid (PAA) and Fe3+ ions with interlacing of the second polymeric chain of polypyrrole (PPy). In this study, ammonium persulfate (APS) was utilized to initiate the polymerization of both acrylic acid and pyrrole. Such hydrogels exhibited good mechanical properties and remarkable self-healing efficiency as well. The self-healing ability of the hydrogels was facilitated by ionic interaction between carboxylic anion groups (COO–) from polyacrylic acid (PAA) and Fe3+ ions. Moreover, the antibacterial activity of the composite hydrogels was examined on Escherichia coli via the disk diffusion method and the zone of inhibition was obtained in the range of 1.26–1.56 cm after incubation for 12 h. In addition, demonstration of the PAA/PPy–Fe composite hydrogels in electrical conductivity applications was performed in which the composite hydrogel was set up in an electrical circuit consisting of an LED and powered by 3 V batteries. The results showed that the electricity could light-up the LED through the PAA/PPy–Fe composite hydrogels and possessed reversible restorability, as indicated by the healed hydrogel consistently lighting-up the LED in the electrical circuit.

Rapid self-healing, stretchable, moldable, antioxidant and antibacterial tannic acid-cellulose nanofibril composite hydrogels

Here, we designed a self-healing composite hydrogel with antioxidant and antibacterial activities by using cellulose nanofibrils (CNF) and tannic acid (TA) as functional additives. Excellent mechanical stability, moldability, stretchability and rapid self-healing ability without any external intervention were realized in one system due to the combined dynamic borate ester bonding between polyvinyl alcohol-borax (PB) and multi-hydrogen bonding between different components. The rheological measurements indicated the incorporation of CNF and TA to PB system substantially affected the viscoelasticity of hydrogels. The unique antioxidant and antibacterial properties were achieved due to the complexation of TA. These high performance multifunctional hydrogels opens a window for a broad application in the field of smart devices and surface engineering.

Rapid Dewatering and Consolidation of Concentrated Colloidal Suspensions: Mature Fine Tailings via Self-Healing Composite Hydrogel.

Billions of tonnes of thick waste streams with highly concentrated colloidal suspensions from different origins have accumulated worldwide, exampled as over 220 km2 mature fine tailings (MFT) from oil sands production in north Alberta. Current treatment technologies are limited by slow yet insufficient water release and sludge consolidation. Herein, a self-healing composite hydrogel system is designed to convert concentrated aqueous colloidal suspensions (e.g., MFT with colloidal solid content >30 wt %) into a dynamic double cross-linked network for rapid dewatering and consolidation. The resultant composite hydrogel demonstrates an excellent dewatering performance so that over 50% of water could be rapidly released within 30 min by vacuum filtration. Furthermore, the formed infinite cross-linked network with self-healing ability can effectively trap fine particles of all sizes and capture small flocs during mechanical mixing, thereby enabling a low solid content at the ppm level in the released water. This new strategy outperforms all the previously reported treatment methods; under mechanical compression, over 80% of water is removed from the MFT, thereby generating a stackable material with >70 wt % solids within an hour. These results demonstrate a highly effective approach and provide insight into the development of advanced materials to tackle the challenging environmental slurry issues.

(Invited) Creating “Double Network” Composites Via Macroscale Reinforcement

The double network concept has been revolutionary in its ability to turn soft, brittle hydrogels into tough, robust materials with mechanical properties that match the best synthetic elastomers. Double network hydrogels consist of two interpenetrating networks, where each network has a specific mechanical response: the “first network” acts as a sacrificial network, consisting of a rigid, extended network with relatively low loading percentage, and the “second network” is a globally percolated, stretchable network. When a double network hydrogel is stretched, covalent bonds of the first network break, dissipating energy; this process continues with increasing strain, until the sacrificial network is completely broken and the second network ruptures. Here, we will utilize this concept to develop materials with analogous fracture properties at the macroscale. Like double network hydrogels, our systems consist of rigid “first networks” embedded in global, soft and stretchable “second networks.” As a control system, 3d printed polyurethane/polyacrylate composite grids were utilized with a synthetic rubber. We found that when the strength of the matrix exceeds the strength of the grid, local fracture occurs in the grid, and stretching is isolated to the rubber in the fractured region. As stretching increases, the force increases, and when the force exceeds the strength of the grid, fracture will occur elsewhere in the composite. This process continues sequentially throughout the sample until all grid fracture sites are exhausted, and the matrix ruptures. By tuning the stiffness of the grid, we can independently control the yield strength and fracture strain of the composite, until a point where the grid strength exceeds the matrix strength, and the multiple fracture process no longer occurs. At an optimized grid:matrix strength ratio, we can then vary the number of fracture sites in the grid, maximizing toughness for a given component combination. The macroscale double network technique enables us to create composites with unique properties. Previously it has been difficult to create composites with hydrogels, because they undergo swelling which results in buckling or delamination in composite samples. We have created new hydrogel composites by incorporating low-melting point alloy (LMA) grids to alleviate this problem. A hydrogel is polymerized around the LMA frame, and the composite structure is submerged in water until the equilibrium swelling conditions are achieved. The sample is then heated to allow the LMA frame to melt, relieving the swelling stress in the composite sample. This LMA frame has been specifically designed based on the macroscale double network criteria to undergo multiple fracture events during stretching. Furthermore, utilizing an LMA frame allows us to stretch the sample up to 250%, fracturing the frame to dissipate energy, return the composite to its original shape, and then “heal” the structure in hot water. These samples can be then annealed in cold water, and retested, with 100% repeatability and healing efficiency. This process introduces new avenues to create self-healing composite hydrogel materials. Figure 1

Facile Soaking Strategy Toward Simultaneously Enhanced Conductivity and Toughness of Self-Healing Composite Hydrogels Through Constructing Multiple Noncovalent Interactions.

Tough and stretchable conductive hydrogels are desirable for the emerging field of wearable and implanted electronics. Unfortunately, most existing conductive hydrogels have low mechanical strength. Current strategies to enhance mechanical properties include employing tough host gel matrices or introducing specific interaction between conductive polymer and host gel matrices. However, these strategies often involve additional complicated processes. Here, a simple yet effective soaking treatment is employed to concurrently enhance mechanical and conductive properties, both of which can be facilely tailored by controlling the soaking duration. The significant improvements are correlated with co-occurring mechanism of deswelling and multiple noncovalent interactions. The resulting optimal sample exhibits attractive combination of high water content (75 wt %), high tensile stress (∼2.5 MPa), large elongation (>600%), reasonable conductivity (∼25 mS/cm), and fast self-healing property with the aid of hot water. The potential application of gel as a strain sensor is demonstrated. The applicability of this method is not limited to conductive hydrogels alone but can also be extended to strengthen other functional hydrogels with weak mechanical properties.