Self-healing Nanocomposite Hydrogels Research Articles

A hyaluronic acid hydrogel as a mild photothermal antibacterial, antioxidant, and nitric oxide release platform for diabetic wound healing

Hyaluronic acid (HA)-based biopolymer hydrogels are promising therapeutic dressings for various wounds but still underperform in treating diabetic wounds. These wounds are extremely difficult to heal and undergo a prolonged and severe inflammatory process due to bacterial infection, overexpression of reactive oxygen species (ROS), and insufficient synthesis of NO. In this study, a dynamic crosslinked hyaluronic acid (HA) hydrogel dressing (Gel-HAB) loaded with allomelanin (AMNP)-N, N′-dis-sec-butyl-N, N′-dinitroso-1, 4-phenylenediamine (BNN6) nanoparticles (AMNP-BNN6) was developed for healing diabetic wounds. The dynamic acylhydrazone bond formed between hydrazide-modified HA (HA-ADH) and oxidized HA (OHA) makes the hydrogel injectable, self-healing, and biocompatible. The hydrogel, loaded with AMNP-BNN6 nanoparticles, exhibits promising ROS scavenging ability and on-demand release of nitric oxide (NO) under near-infrared (NIR) laser irradiation to achieve mild photothermal antibacterial therapy (PTAT) (∼ 48 °C). Notably, the Gel-HAB hydrogel effectively reduced the oxidative stress level, controlled infections, accelerated vascular regeneration, and promoted angiogenesis, thereby achieving rapid healing of diabetic wounds. The injectable self-healing nanocomposite hydrogel could serve as a mild photothermal-enhanced antibacterial, antioxidant, and nitric oxide release platform for the treatment of diabetic wounds.

Fabrication of anti-freezing and self-healing nanocomposite hydrogels based on phytic acid and cellulose nanocrystals for high strain sensing applications.

For hydrogel-based flexible sensors, it is a challenge to enhance the stability at sub-zero temperatures while maintaining good self-healing properties. Herein, an anti-freezing nanocomposite hydrogel with self-healing properties and conductivity was designed by introducing cellulose nanocrystals (CNCs) and phytic acid (PA). The CNCs were grafted with polypyrrole (PPy) by chemical oxidation, which were used as the nanoparticle reinforcement phase to reinforce the mechanical strength of hydrogels (851.8%). PA as a biomass material could form strong hydrogen bond interactions with H2O molecules, endowing hydrogels with prominent anti-freezing properties. Based on the non-covalent interactions, the self-healing rate of the hydrogels reached 92.9% at -15 °C as the content of PA was 40.0 wt%. Hydrogel-based strain sensors displayed high sensitivity (GF = 0.75), rapid response time (350 ms), good conductivity (3.1 S m-1) and stability at -15 °C. Various human movements could be detected by using them, including small (smile and frown) and large changes (elbow and knee bending). This work provides a promising method for the development of flexible wearable sensors that work stably in frigid environments.

Self-healing nanocomposite hydrogels based on chitosan/ modified polyethylene glycol/graphene

The aim of this research is to prepare self-healing injectable nanocomposite hydrogels based on benzaldehyde-modified polyethylene glycol and chitosan, reinforced with graphene oxide (GO) for the delivery of pomegranate extract (PG) for hard tissue engineering. For this purpose, polyethylene glycol (PEG) was first modified by an aldehyde agent and mixed with chitosan to form hydrogels based on reversible Schiff-Base linkages. Nanocomposites were prepared with the addition of 0.5, 1.0, 1.5, and 2.0 wt% GO to the hydrogels. Then, PG was loaded into the final nanocomposite hydrogels as the drug model to promote cell proliferation and chondrogenesis. The scanning electron microscopy (SEM) images indicated that the incorporation of GO into the hydrogels increased the average pore size from 261 to 403 µm, resulting in a favorable porous structure. The results also showed an enhancement in the elastic properties as well as the compressive strength of the nanocomposite hydrogels with increasing GO content. The drug release profile followed a power-law kinetics, in which, the content of PG and GO affected the release rate. According to self-healing and injection tests, all the hydrogels had good injection and self-healing capabilities. The incorporation of GO into the hydrogel increased antibacterial properties to more than 99%. The in vitro assay indicated that PG loading provided a suitable environment for the growth and survival of cells on the hydrogels. Therefore, the designed system is a promising framework for the local delivery of pharmaceuticals for hard tissue engineering.

Dynamics of Nanocomposite Hydrogel Alignment during 3D Printing to Develop Tissue Engineering Technology.

Taking inspiration from spider silk protein spinning, we developed a method to produce tough filaments using extrusion-based 3D bioprinting and salting-out of the protein. To enhance both stiffness and ductility, we have designed a blend of partially crystalline, thermally sensitive natural polymer gelatin and viscoelastic G-polymer networks, mimicking the components of spider silk. Additionally, we have incorporated inorganic nanoparticles as a rheological modifier to fine-tune the 3D printing properties. This self-healing nanocomposite hydrogel exhibits exceptional mechanical properties, biocompatibility, shear thinning behavior, and a well-controlled gelation mechanism for 3D printing.

Fabrication of amphoteric gelatin nanospheres-doped self-healing nanocomposite hydrogels and the application in flexible sensors

The nanomaterials with two distinct properties or components have outstanding advantages in the synthesis of smart hydrogels. In this work, gelatin nanospheres (GNPs) asymmetrically coated with poly(diallyldimethylammonium chloride) (PDDA) and tannic acid (TA) were synthesized by Pickering emulsion template method. The nanocomposite hydrogel with amphoteric gelatin nanospheres (GPTNPs)-doped was successfully prepared, which has excellent mechanical properties (strain = 616%, stress = 2.85 MPa) and self-healing properties (efficiency = 90.9%) under the synergistic effects of hydrogen bonding and metal coordination. The developed GPTNPs/polyacrylic acid (GPTNPs/PAA) hydrogel sensor exhibits high sensitivity (gauge factor (GF) = 3.69), quick response time (96.4 ms) and superior stability. Therefore, the GPTNPs/PAA hydrogels are excellent materials for application in wearable flexible sensors to monitor real-time human motion.

Dual detection of human motion and glucose in sweat with polydopamine and glucose oxidase doped self-healing nanocomposite hydrogels

The detection of human motion and sweat composition are important for human health or sports training, so it is necessary to develop flexible sensors for monitoring exercise processes and sweat detection. Mussel secretion of adhesion proteins enables self-healing of byssus and adhesion to surfaces. We prepared Au nanoparticles@polydopamine (AuNPs@PDA) nanomaterials based on mussel-inspired chemistry and compounded them with polyvinyl alcohol (PVA) hydrogels to obtain PVA/AuNPs@PDA self-healing nanocomposite hydrogels. Dopamine (DA) was coated on the surface of AuNPs to obtain AuNPs based composite (AuNPs@PDA) and the AuNPs@PDA was implanted into the PVA hydrogels to obtain nanocomposite hydrogel through facile freeze-thaw cycle. Glucose oxidase (GOD) was added to the hydrogel matrix to achieve specific detection of glucose in sweat. The obtained hydrogels exhibit high deformability (573.7 %), excellent mechanical strength (550.3 KPa) and self-healing properties (85.1 %). The PVA/AuNPs@PDA hydrogel sensors exhibit quick response time (185.0 ms), wide strain sensing range (0–500 %), superior stability and anti-fatigue properties in motion detection. The detection of glucose had wide concentration detection range (1.0 μmol/L-200.0 μmol/L), low detection limits (0.9 μmol/L) and high sensitivity (24.4 μA/mM). This work proposes a reference method in dual detection of human exercise and sweat composition analysis.

Phytic acid assist for self-healing nanocomposite hydrogels and their application in flexible strain sensors

Nanocomposite hydrogels have been applied in the field of flexible sensors to monitor human body signals. In this manuscript, phytic acid (PA) was successfully adsorbed on the surface of graphene oxide@polydopamine (GO@PDA). The obtained graphene oxide@polydopamine-phytic acid (GO@PDA-PA) was further implanted to the poly acrylic acid (PAA) hydrogels as flexible strain sensors. Dopamine (DA) was self-polymerized on both two sides of GO by mussel-inspired chemistry to synthetize GO@PDA. PA was decorated on the surface of GO@PDA to obtain GO@PDA-PA nanocomposites with Pickering emulsion in oil-in-water (O/W) emulsion. The GO@PDA-PA hydrogels’ self-healing efficiency (98.6%) and mechanical strength (1.77 MPa) were both improved due to the presence of reversible interaction such as hydrogen bond and metal-ligand coordination. The wearable flexible sensors based on the prepared GO@PDA-PA hydrogels have high sensitivity (gauge factor (GF) = 3.3), stability, durability and high response ability. It can detect the sharp movement signals of human body and tiny movement signals such as breathing. The excellent performance of nanocomposite hydrogels is expected to promote the evolution of flexible sensors.

Fabrication of anti-freezing and self-healing nanocomposite hydrogels based on zwitterionic proline and cellulose nanocrystals

Self-healing hydrogels with three-dimensional network cross-linked structure and adjustable properties have been considered as smart materials with promising multi-purpose applications. However, traditional self-healing hydrogels face the loss of mechanical properties at sub-zero temperatures, which may limit their application in various fields to some extent. In this manuscript, functional polydopamine (PDA) was successfully chemically modified on the surface of cellulose nanocrystals (CNCs) by self-oxidation polymerization in an alkaline environment. The nanocomposite hydrogels with self-healing and anti-freezing properties were successfully designed by introducing zwitterionic proline (ZP) and CNCs@PDA into the cross-linked network structure of gellan gum/polyacrylic acid (GG/PAA). When the ZP ratio increased, the anti-freezing performance of hydrogels was significantly enhanced. Even at −30 °C, the GG/PAA-CNCs@PDA-ZP-Ca2+ (GP/CP/ZP/Ca2+) nanocomposite hydrogels still maintain excellent stress (2.7 MPa) and high self-healing efficiency (82.9%). This work proposes an effective solution to prepare flexible hydrogels with anti-freezing capability, which will extend the temperature range of the flexible material and broaden the application area.

GBAP/L-proline assist of self-healing nanocomposite hydrogels and their applications in antifreeze, high-sensitivity flexible sensors

For novel wearable flexible electronics, the design of hydrogels materials with anti-freezing capability is of great significance to meet the mechanical flexibility and smart sensing at cryogenic temperatures. Herein, glycosyl cross-linking boron acid and ammonium salt of phytic acid (PA) (GBAP) was synthesized based on eco-friendly organic materials, which was successfully wrapped on the surface of graphene oxide (GO) to obtain GO@GBAP. L-proline (L-Pro) as an antifreeze zwitterion and GO@GBAP were implanted in polyvinyl alcohol (PVA) and xanthan gum (XG) three-dimensional network structure. PA with antifreeze property was further introduced as a crosslinking agent, the PVA-XG/GO@GBAP/PA/L-Pro (PGPL) composite hydrogels were successfully prepared. While at −20°C, the PGPL hydrogels had remarkable mechanical strength (0.80 MPa), and they revealed the splendid self-healing efficiency (89.2%) after 4 h of healing. The high-sensitivity flexible sensors based on these PGPL hydrogels exhibited a rapid response time (220.0 ms) and electrical conductivity (detection mean 2.1 S/m at −20°C). Even at −20°C for 24 h, it could still respond to various physical and physiological movements such as swallowing and wrist activities. This nanocomposite hydrogels constructed in this work had expanded their application scope in the field of cryogenic sensing.

Phytic acid-assist for self-healing nanocomposite hydrogels with surface functionalization of cellulose nanocrystals via SI-AGET ATRP

Phytic acid-assist for self-healing nanocomposite hydrogels with surface functionalization of cellulose nanocrystals via SI-AGET ATRP

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.

Fabrication of Janus-type nanocomposites from cellulose nanocrystals for self-healing hydrogels’ flexible sensors

Janus bio-nanomaterials have great application potential in functional solid surfactants, probes and flexible sensors. In this manuscript, the sustainable Janus cellulose nanocrystals-type (CNCs-type) nanomaterials were prepared by Pickering emulsion template method. The asymmetric functionalism of Janus nanorods was realized by asymmetrically grafting polypyrrole (PPy) and polydopamine (PDA) onto different sides of CNCs (Janus CNCs-PPy /PDA (JCNs)). JCNs was successfully applied to self-healing nanocomposite hydrogels and further applied to the development of flexible sensors. The self-healing efficiency of nanocomposite hydrogels was 87.2%, and the stress and strain reached 3.50 MPa and 453.45%, respectively. It is worth noting that flexible sensors have been widely used in the field of wearable electronic sensing for real-time monitoring of human movement due to their high sensitivity (gauge factor (GF) = 9.9) and fast response time (260 ms).

A self-healing nanocomposite hydrogel electrolyte for rechargeable aqueous Zn-MnO2 battery

Hydrogel electrolytes are an attractive class of conductive materials for flexible energy storage devices given their reassuring flexibility and stable electrochemical performance. However, it still remains a challenge to assemble the smart battery with mechanical stability and self-healing property when suffering from inevitable physical damages. Here, a novel Zn2+-based polyacrylamide/halloysite nanotubes (PAAm/HNTs) nanocomposite hydrogel electrolyte is designed and prepared through rigid HNTs doped into the chemical cross-linked PAAm network. The PAAm/HNTs hydrogel with tensile performance, self-healing property and extended Zn2+ transport channels was used as hydrogel electrolyte in Zn/MnO2 batteries which possess an initial capacity of 347 mA h g1 at a current density of 0.2 A g–1 with good cycle stability. This work offers an effective design method to improve strength, self-healing and fatigue resistance of nanocomposite hydrogel electrolytes which would provide alterative view for the construct of hydrogel electrolytes with desirable properties.

Anti-freezing and self-healing nanocomposite hydrogels based on poly(vinyl alcohol) for highly sensitive and durable flexible sensors

For the new generation of wearable flexible electronic devices, it is urgent to achieve higher requirements for the realization of anti-freezing properties. Herein, a strategy was successfully designed to fabricate flexible sensors that could withstand at −30 °C. Functional poly(diallyldimethylammonium chloride) (PDDA) were successfully grafted onto the surface of cellulose nanocrystals (CNCs) by electrostatic interaction. As biomass acid, phytic acid (PA) with anti-freezing properties were further introduced as crosslinking agents, poly(vinyl alcohol) (PVA)/CNCs@PDDA/PA (PCP) nanocomposite hydrogels were successfully fabricated through facile freeze–thaw cycle in the water/glycerol binary solvent system. With the increase of PA ratio, the anti-freezing performance of hydrogels is improved obviously. The obtained hydrogels still maintain favorable mechanical strength (1.0 MPa) and self-healing efficiency (85.0%) after healing about 4 h at −30 °C. Hydrogels based flexible sensors exhibit fast response time (310.0 ms), wide strain detection range (0.0 ∼ 600.0%), excellent stability and fatigue resistance, which can also perform excellent human motion signal detection tasks even at −30 °C for 24 h. This work paves the way for the application of wearable flexible electronic devices in extreme climate areas.

Stretchable, rapid self-healing guar gum-poly(acrylic acid) hydrogels as wearable strain sensors for human motion detection based on Janus graphene oxide

Wearable strain sensors have received widespread attention in research fields due to their applications in human motion detection. In this manuscript, the fabrication of functionalized Janus graphene oxide (GO) nanosheets were used by Pickering emulsion template. Polypyrrole (PPy) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) were asymmetrically grafted on the two sides of GO (GO@PPy/PDMAEMA Janus NS), which successfully applied to synthesize Janus NS/guar gum-poly(acrylic acid) (GG-PAA) self-healing nanocomposite hydrogels. The outstandingly improved self-healing efficiency (92.8% for 2 h) and mechanical properties (strength of 4.12 MPa and toughness of 873.8%) of nanocomposite hydrogels were mainly supported by the collaborative effect of reversible electrostatic interactions, multiple hydrogen bonds and metal-ligand coordination. Moreover, the hydrogels exhibited strain sensitivity and could be able to monitor a variety of human motions, which have outstanding application prospects in wearable flexible sensors.

Surface engineering of cellulose nanocrystals via SI-AGET ATRP of glycidyl methacrylate and ring-opening reaction for fabricating self-healing nanocomposite hydrogels

Surface engineering of cellulose nanocrystals via SI-AGET ATRP of glycidyl methacrylate and ring-opening reaction for fabricating self-healing nanocomposite hydrogels

Self-healing nanocomposite hydrogels via Janus nanosheets: Multiple effects of metal–coordination and host–guest interactions

Recently years, hydrogels have received increased attention due to their promising applications in wound dressing, tissue engineering, biosensors and human-machine interfaces. However, designing hydrogels with good mechanical strength and self-healing ability remains a challenge. As a novel strategy, functional Janus nanosheets (JNs) were used as reinforcement to develop self-healing nanocomposite hydrogels. Herein, the silica Janus hollow spheres were prepared by a sol-gel process, modified with poly(2-(acryloyloxy)ethyl ferrocenecarboxylate)(PMAEFc)/polydopamine(PDA) to the internal/external surfaces and then crushed to fabricate the SiO2@PMAEFc/PDA JNs. The SiO2@PMAEFc/PDA JNs were then used as robust reinforcement to design self-healing nanocomposite hydrogels. Based on multiple effects of metal–coordination and host–guest interactions, the mechanical strengths and self-healing properties of hydrogels were both enhanced. Specially, after introducing JNs, the rupture stress of hydrogels increased from 1.27 MPa to 2.23 MPa, and the self-healing efficiency improved from 66.7% to 92.4%. These results demonstrate that JNs can be used as robust reinforcement to fabricate self-healing nanocomposite hydrogels, which enriches the design of self-healing hydrogels and broadens the application prospects of Janus nanomaterials.

Silica-based Janus nanosheets for self-healing nanocomposite hydrogels

As functional nanocomposites, Janus nanomaterials can play an important role due to their asymmetric structure and different components on the same surface. In this manuscript, hollow silicon spheres (SiO2 JHs) with an asymmetric structure were prepared by an emulsion interfacial self-organized sol-gel process. Inspired by mussel chemistry, the exposed surfaces of the SiO2 JHs were modified chemically by polydopamine (PDA). 2-(3-(6-Methyl-4-oxo-1,2,3,4-tetrahydropyrimidin-2-yl)ureido)ethyl methacrylate (MAUPy) containing multiple hydrogen bond groups were grafted to obtain SiO2@PDA/PMAUPy Janus Nanosheets (SiO2@PDA/PMAUPy JNs) by Pickering emulsion. The prepared SiO2@PDA/PMAUPy JNs were further applied to prepare nanocomposite self-healing hydrogels. As a result of the synergy of reversible non-covalent metal-ligand and hydrogen bonding, hydrogels with dual self-healing feature were successfully fabricated. The obtained hydrogels maintain preferable mechanical properties (strain of about 411.0% and stress of about 4.1 MPa) and excellent healing ratio (92.6%), which may have broad application prospects in smart flexible sensor and biomedical application.

Fabrication of self-healing nanocomposite hydrogels with the cellulose nanocrystals-based Janus hybrid nanomaterials

Janus nanomaterials possess remarkable prospects in the design of a series of smart materials with unique asymmetric properties. In this work, surface functionalized Janus cellulose nanocrystalline-type (CNCs-type) nanomaterials were manufactured by Pickering emulsion template and the construction of self-healing nanocomposite hydrogels has been realized. During emulsification, the mussel-inspired chemistry was employed to develop Janus nanocomposites. The extension of molecular chain of poly-lysine (PLL) and the polydopamine (PDA) coating were grafted on different sides of CNCs. Afterwards, the prepared nanocomposites were added to poly (acrylic acid) (PAA)-based hydrogels which formed by in-situ polymerization. The collaborative effect of metal-ligand coordination between the molecular chain of PLL, PDA coating, PAA chains and metal ions endowed the nanocomposite hydrogels with excellent mechanical properties (8.8 MPa) and self-healing efficiency (88.9%). Therefore, the synthesized Janus CNCs-PDA/PLL nanocomposites are expected to have diverse application in the development of smart materials with self-healing ability.

Self-healing and toughness cellulose nanocrystals nanocomposite hydrogels for strain-sensitive wearable flexible sensor

Recently, self-healing and high mechanical strength hydrogels have aroused much research due to their potential future in strain-sensitive flexible sensors. In this manuscript, we successfully designed self-healing and toughness cellulose nanocrystals (CNCs) nanocomposite hydrogels by grafted polypyrrole (PPy) on the surface of CNCs to enhance electrical conductivity. The obtained nanocomposite hydrogels exhibit outstanding self-healing and mechanical behaviors, and the optimal mechanical strength, toughness and self-healing efficiency can be up to 5.7 MPa, 810% and 89.6%, respectively. Using these functional nanocomposite hydrogels, strain-sensitive wearable flexible sensors were designed to monitor finger joint motions, bending of knee, and even the slight pulse beating. Surprisingly, the flexible sensors could evidently perceive body motions from large movements (knee bending) to tiny signals (pulse beating). In addition, it exhibited excellent durability after repeated cycles. This method of prepared self-healing nanocomposite hydrogels will have a potential prospect in the design of biomedical, biosensors, and flexible electronic devices.