Conventional Hydrogels Research Articles

Smart Responsive and Controlled-Release Hydrogels for Chronic Wound Treatment.

Chronic wounds are a major health challenge that require new treatment strategies. Hydrogels are promising drug delivery systems for chronic wound healing because of their biocompatibility, hydration, and flexibility. However, conventional hydrogels cannot adapt to the dynamic and complex wound environment, which involves low pH, high levels of reactive oxygen species, and specific enzyme expression. Therefore, smart responsive hydrogels that can sense and respond to these stimuli are needed. Crucially, smart responsive hydrogels can modulate drug release and eliminate pathological factors by changing their properties or structures in response to internal or external stimuli, such as pH, enzymes, light, and electricity. These stimuli can also be used to trigger antibacterial responses, angiogenesis, and cell proliferation to enhance wound healing. In this review, we introduce the synthesis and principles of smart responsive hydrogels, describe their design and applications for chronic wound healing, and discuss their future development directions. We hope that this review will inspire the development of smart responsive hydrogels for chronic wound healing.

Magnetic nanocomposite hydrogel with ultra‐stretchable as strain sensors for monitoring human motion and the change of magnetic field

AbstractIn recent years, the smart hydrogels have gained much concern in the field of research specially related to flexible strain sensors because they exhibit many types of smart interactions that can be useful in wearable devices. However, the conventional hydrogels have poor electrical conductivity that affect the performance of the sensors, so it remains a challenge to achieve noncontact signal monitoring (e.g., for the detection of magnetic field changes). In this study, an ultra‐stretchable and magnetically responsive conductive hydrogel was fabricated by adding magnetic ferric tetroxide@polypyrrole composite nanoparticles (Fe3O4@PPy NPs) to polyacrylamide (PAm). The nanoparticles were easily agglomerated and improved the compatibility of PPy and hydrogel. The obtained PAm/Fe3O4@PPy hydrogel showed an ultra‐stretchability of (961%), a low elastic modulus of (87.8 kPa), and an excellent toughness of (1010.5 kJ m−3). Moreover, PAm/Fe3O4@PPy hydrogel also exhibited a high electrical conductivity of 0.34 S m−1, and the PAm/Fe3O4@PPy hydrogel sensor could detect human motions (such as bending of finger, bending of wrist) and muscle micromotion (such as pronouncing). In addition, it can also monitor the change in magnitude of magnetic field.

Guiding bone cell network formation in 3D via photosensitized two-photon ablation

A long-standing challenge in skeletal tissue engineering is to reconstruct a three-dimensionally (3D) interconnected bone cell network in vitro that mimics the native bone microarchitecture. While conventional hydrogels are extensively used in studying bone cell behavior in vitro, current techniques lack the precision to manipulate the complex pericellular environment found in bone. The goal of this study is to guide single bone cells to form a 3D network in vitro via photosensitized two-photon ablation of microchannels in gelatin methacryloyl (GelMA) hydrogels. A water-soluble two-photon photosensitizer (P2CK) was added to soft GelMA hydrogels to enhance the ablation efficiency. Remarkably, adding 0.5 mM P2CK reduced the energy dosage threshold five-fold compared to untreated controls, enabling more cell-compatible ablation. By employing low-energy ablation (100 J/cm2) with a grid pattern of 1 µm wide and 30 µm deep microchannels, we induced dendritic outgrowth in human mesenchymal stem cells (hMSC). After 7 days, the cells successfully utilized the microchannels and formed a 3D network. Our findings reveal that cellular viability after low-energy ablation was comparable to unablated controls, whereas high-energy ablation (500 J/cm2) resulted in 42 % cell death. Low-energy grid ablation significantly promoted network formation and >40 µm long protrusion outgrowth. While the broad-spectrum matrix metalloproteinase inhibitor (GM6001) reduced cell spreading by inhibiting matrix degradation, cells invaded the microchannel grid with long protrusions. Collectively, these results emphasize the potential of photosensitized two-photon hydrogel ablation as a high-precision tool for laser-guided biofabrication of 3D cellular networks in vitro. Statement of SignificanceThe inaccessible nature of osteocyte networks in bones renders fundamental research on skeletal biology a major challenge. This limit is partly due to the lack of high-resolution tools that can manipulate the pericellular environment in 3D cultures in vitro. To create bone-like cellular networks, we employ a two-photon laser in combination with a two-photon sensitizer to erode microchannels with low laser dosages into GelMA hydrogels. By providing a grid of microchannels, the cells self-organized into a 3D interconnected network within days. Laser-guided formation of 3D networks from single cells at micron-scale resolution is demonstrated for the first time. In future, we envisage in vitro generation of bone cell networks with user-dictated morphologies for both fundamental and translational bone research.

A Facilely Prepared Adhesive Dressing Derived from Non-Ionic Hydrogel for Accelerated Diabetic Wound Healing

Hydrogels are an important category of polymeric materials with physicochemical features such as moisturizability and biocompatibility that are ideal for developing dressings for diabetic wounds. However, conventional non-ionic hydrogel materials generally exhibit poor mechanical properties and poor adhesion, which compromise their ability to self-sustain in mechanically dynamic wound microenvironments. In this research, we developed a hybrid hydrogel as a highly biocompatible adhesive wound dressing that met the mechanical requirements of the skin to promote chronic wound healing in diabetic mouse models. A 7.5% (w/v) hydrogel corresponded to a Young’s modulus of 6.3 kPa. In vitro cell-based and subcutaneous implantation experiments in mice demonstrated the excellent biocompatibility and optimal biodegradability of hydrogel dressings. In a diabetic mouse splint wound model for evaluating wound healing in vivo, the hydrogel dressing showed robust adhesion to the wound and efficiently accommodated mechanical deformations around the wound, resulting in significantly improved healing rates of chronic diabetic wounds. Thus, our work illustrates a newly alternative strategy for the simple and efficacious treatment of chronic wounds in the context of diabetes care.

Ferritin-Based Nanocomposite Hydrogel Promotes Tumor Penetration and Enhances Cancer Chemoimmunotherapy.

Hydrogels are prevailing drug delivery depots to improve antitumor efficacy and reduce systemic toxicity. However, the application of conventional free drug-loaded hydrogel is hindered by poor drug penetration in solid tumors. Here, an injectable ferritin-based nanocomposite hydrogel is constructed to facilitate tumor penetration and improve cancer chemoimmunotherapy. Specifically, doxorubicin-loaded human ferritin (Dox@HFn) and oxidized dextran (Dex-CHO) are used to construct the injectable hydrogel (Dox@HFn Gel) through the formation of pH-sensitive Schiff-base bonds. After peritumoral injection, the Dox@HFn Gel is retained locally for up to three weeks, and released intact Dox@HFn gradually, which can not only facilitate tumor penetration through active transcytosis but also induce immunogenic cell death (ICD) to tumor cells to generate an antitumor immune response. Combining with anti-programmed death-1 antibody (αPD-1), Dox@HFn Gel induces remarkable regression of orthotopic 4T1 breast tumors, further elicits a strong systemic anti-tumor immune response to effectively suppress tumor recurrence and lung metastasis of 4T1 tumors after surgical resection. Besides, the combination of Dox@HFn GelL with anti-CD47 antibody (αCD47) inhibits postsurgical tumor recurrence of aggressive orthotopic glioblastoma tumor model and significantly extends mice survival. This work sheds light on the construction of local hydrogels to potentiate antitumor immune response for improved cancer therapy.

An electroconductive hydrogel with injectable and self-healing properties accelerates peripheral nerve regeneration and motor functional recovery

Peripheral nerve regeneration and functional recovery are slow due to disruption of bioelectrical signal transmission. As a new therapeutic strategy, conductive hydrogels have been shown to promote the regeneration of electroactive tissue, especially nerve tissue. However, conventional conductive hydrogels made of physically doped conductive particles suffer from fragility, agglomeration, poor durability, and discontinuous transmission of electrical signals, severely limiting the migration of Schwann cells (SCs) and the remyelination of axons. Herein, a novel water-soluble conductive material was synthesized by grafting polyaniline (PANI) onto carboxymethyl chitosan (CMCS). Dual cross-linked hydrogels with injectable, self-healing, and conductive properties were created by adding CMCS-PANI (CP) to the dynamic gel network generated by the Schiff base reaction between aldehyde-based hyaluronic acid (ALHA) and CMCS. The prepared self-healing ALHA/CMCS/CP (ACCP) hydrogel had good biocompatibility, elastic modulus, and electrical conductivity that matched the sciatic nerve. The in vitro experiments indicated that ACCP3 (3 wt% CP) promoted the proliferation and migration of the SCs. Injection of ACCP3 into the crush injury site of the sciatic nerve reduced tissue resistivity, increased nerve conduction velocity, decreased the sciatic nerve functional index, enhanced the expression of neuronal axon-specific proteins, induced axon extension and remyelination, and prevented muscle denervation atrophy. Overall, the injectable self-healing conductive ACCP3 hydrogel, as a safe and effective neural tissue substitute, opens up a new way for the treatment of peripheral nerve injury and has potential clinical application.

Advancing neural regeneration via adaptable hydrogels: Enriched with Mg2+ and silk fibroin to facilitate endogenous cell infiltration and macrophage polarization

Peripheral nerve injury is a complex and challenging medical condition due to the limited ability of nerves to regenerate, resulting in the loss of both sensory and motor function. Hydrogels have emerged as a promising biomaterial for promoting peripheral nerve regeneration, while conventional hydrogels are generally unable to support endogenous cell infiltration due to limited network dynamics, thereby compromising the therapeutic outcomes. Herein, we present a cell adaptable hydrogel containing a tissue-mimetic silk fibroin network and a dynamically crosslinked bisphosphonated-alginate network. The dynamic network of this hydrogel can respond to cell-generated forces to undergo the cell-mediated reorganization, thereby effectively facilitating the rapid infiltration of Schwann cells and macrophages, as well as the ingrowth of axons. We further show that the magnesium ions released from the hydrogel not only promote neurite outgrowth but also regulate the polarization of macrophages in a sequential manner, contributing to the formation of a regenerative microenvironment. Therefore, this hydrogel effectively prevents muscle atrophy and promotes the regeneration and functional recovery of nerve defects of up to 10 mm within 8 weeks. The findings from this study demonstrate that adaptable hydrogels are promising inductive biomaterials for enhancing the therapeutic outcomes of peripheral nerve injury treatments.

Polydopamine-triggered adhesive and conductive hydrogel for Morse code communication at polar environments

Flexible electronics have been extensively explored for health monitoring and soft robotics. However, conventional hydrogels are inevitably frozen in polar environments and easily dehydrated, and have weak surface adhesion. Inspired by the natural mussel adhesive mechanism, we designed a polydopamine-polyacrylamide-LiCl (PPL) hydrogel with high electrical conductivity, high stretchability, and strong surface adhesion under low-temperature conditions. The PPL hydrogel exhibits robust adhesion (68.8 kPa), high electrical conductivity (384 S m−1 at room temperature, and 26 S m−1 at −40 °C), superior stretchability (1200%), and cycling stability (3000 cycles). The hydrogel sensor can accurately measure human joint movements, making them suitable for use in information encryption and decryption through Morse code even in polar environments (−60 °C). Further research in this area can lead to innovative solutions for communication and health monitoring in extreme conditions.

Nanoengineered injectable hydrogels derived from layered double hydroxides and alginate for sustained release of protein therapeutics in tissue engineering applications

Chronic Kidney Disease (CKD) which involves gradual loss of kidney function is characterized by low levels of a glycoprotein called Erythropoietin (EPO) that leads to red blood cell deficiency and anemia. Recombinant human EPO (rhEPO) injections that are administered intravenously or subcutaneously is the current gold standard for treating CKD. The rhEPO injections have very short half-lives and thus demands frequent administration with a risk of high endogenous EPO levels leading to severe side effects that could prove fatal. To this effect, this work provides a novel approach of using lamellar inorganic solids with a brucite-like structure for controlling the release of protein therapeutics such as rhEPO in injectable hydrogels. The nanoengineered injectable system was formulated by incorporating two-dimensional layered double hydroxide (LDH) clay materials with a high surface area into alginate hydrogels for sustained delivery. The inclusion of LDH in the hydrogel network not only improved the mechanical properties of the hydrogels (5–30 times that of alginate hydrogel) but also exhibited a high binding affinity to proteins without altering their bioactivity and conformation. Furthermore, the nanoengineered injectable hydrogels (INHs) demonstrated quick gelation, injectability, and excellent adhesion properties on human skin. The in vitro release test of EPO from conventional alginate hydrogels (Alg-Gel) showed 86% EPO release within 108 h while INHs showed greater control over the initial burst and released only 24% of EPO in the same incubation time. INH-based ink was successfully used for 3D printing, resulting in scaffolds with good shape fidelity and stability in cell culture media. Controlled release of EPO from INHs facilitated superior angiogenic potential in ovo (chick chorioallantoic membrane) compared to Alg-Gel. When subcutaneously implanted in albino mice, the INHs formed a stable gel in vivo without inducing any adverse effects. The results suggest that the proposed INHs in this study can be utilized as a minimally invasive injectable platform or as 3D printed patches for the delivery of protein therapeutics to facilitate tissue regeneration.

Poly(N‐acryloyl glycinamide) eutectogels

AbstractThe ever‐growing demand for advanced implantable and wearable electronics has stimulated the development of conductive gels with desirable functions. Hydrogels suffer from poor environmental adaptability. The ionogels prepared by dissolving polymers in ionic liquids have to face the problems of high cost of synthesis and biotoxicity concerns. Recently, eutectogels consisting of various polymer networks in eco‐friendly and cost‐effective deep eutectic solvents (DESs) have emerged as attractive alternatives to overcome the limitations associated with conventional hydrogels and ionogels. In this study, a kind of eutectogels was designed and synthesized through one‐step in situ photopolymerization of N‐acryloyl glycinamide (NAGA) without crosslinkers in low‐cost and biosafe DESs composed of choline chloride and ethylene glycol. The obtained poly(N‐acryloyl glycinamide) (PNAGA) eutectogels exhibit concentration‐dependent and adjustable mechanical properties, high electrical conductivity (about 2 mS cm−1), self‐healing ability as well as good anti‐drying and anti‐freezing properties. PNAGA eutectogels were also demonstrated to serve as conductive gels to construct pressure sensors over a relatively large temperature range. Considering the simple and easy‐to‐scale preparation process and commercially available low‐cost raw materials, favorable flexibility, high ionic conductivity, and wide‐climate tolerance, the PNAGA eutectogels as soft conductive materials have great potential for use in the fabrication of flexible electronics.

Designing Antifreezing Hydrogels with Enhanced Mechanical Properties Using a Simple Crosslinker

Antifreezing hydrogels are essential for materials design and practical applications, but their development and understanding have been challenging due to their high-water content. Current antifreezing hydrogels typically rely on organic solvents or the addition of antifreezing agents. In this study, we present a novel crosslinking strategy to fabricate antifreezing hydrogels without the need for additional antifreezing agents. We introduce a new crosslinker, PEGn-EGINA, which combines highly hydrophilic EGINA with polyethylene glycol (PEG) of varying molecular weights. Utilizing PEGn-EGINA as the crosslinker, we synthesize Agar/Polyacrylamide (Agar/PAAm) double-network hydrogels, alongside conventional MBAA-crosslinked hydrogels for comparison. The resulting PEGn-EGINA-crosslinked hydrogels exhibit inherent antifreezing properties and retain their mechanical integrity even at subzero temperatures for extended periods. Molecular dynamics (MD) simulations further reveal that the antifreezing behavior observed in the PEGn-EGINA-crosslinked hydrogels can be attributed to their highly hydrophilic and tightly crosslinked double-network structures. These structures enable strong bindings between water and the hydrogel network, thus effectively preventing the formation of ice crystals within the hydrogels. Notably, PEGn-EGINA-crosslinked hydrogels not only demonstrate superior mechanical performance compared to MBAA-crosslinked hydrogels, but also maintain their mechanical properties even in frozen conditions, making them suitable for a wide range of applications. This study presents a simple yet effective design concept for highlighting the role of novel crosslinker in enhancing antifreezing and mechanical properties, showcasing their potential for various applications that require both antifreezing capabilities and robust mechanical performance.

Multiple dynamic interaction-enabled eutectogel with strong tissue adhesion, mechanical strength and temperature tolerance for transdermal drug delivery: Double monodentate coordination and π-π interaction

The application of conventional hydrogels in transdermal drug delivery system (TDDS) is limited due to their inability to provide high adhesion and cohesive strength simultaneously. Additionally, hydrogels are vulnerable to temperature fluctuations, which can cause freezing or dehydration, leading to a loss of adhesion and cohesion, thereby failing to ensure steady drug delivery. In this study, taking inspiration from natural mussels and deep eutectic solvents (DES), we introduce the calcium ion-coordinated p-hydroxyphenyl methacrylate (HP-Ca2+) eutectogel utilizing choline chloride-ethylene glycol (ChCl-EG) DES as solvents, by virtue of coordination bond-enabled multiple dynamic interactions (MDI) to fully substitute conventional covalent crosslinking. This novel eutectogel exhibits remarkable properties that surpass those of conventional hydrogels applied in TDDS. These properties include exceptional stretchability (>1600 %), high tensile strength (>300 kPa), strong skin adhesion (>30 kPa), and excellent temperature tolerance (-25–60 °C). We have demonstrated that remarkable features of HP-Ca2+ eutectogel are achieved through MDI, specifically double monodentate coordination, strong π-π interaction, and double hydrogen bond, characterized by XPS, ITC and 2D NMR. The synergistic effects of MDI provide numerous non-covalent crosslinking sites, improving cohesive strength, and serving as an integrated platform for tailoring interfacial properties to enhance adhesion. Furthermore, the HP-Ca2+ eutectogel exhibits exceptional thermal stability and controlled release capabilities for transdermal drug delivery. Through comprehensive evaluations, the HP-Ca2+ eutectogel emerges as a highly effective solution for developing transdermal drug delivery patches.

Enhancing the mechanical properties of hydrogels with vinyl-functionalized nanocrystalline cellulose as a green crosslinker

Hydrogels have gained significant attention in scientific communities for their versatile applications, but several challenges need to be addressed to exploit their potential fully. Conventional hydrogels suffer from poor mechanical strength, limiting their use in many applications. Moreover, the crosslinking agents used to produce them are often toxic, carcinogenic, and not bio-friendly. This study presents a novel approach to overcome these limitations by using bio-friendly modified nanocrystalline cellulose as a crosslinker to prepare highly stretchable and tough thermosensitive hydrogels. The surface of nanocrystalline cellulose was modified with 3-methacryloxypropyltrimethoxysilane (MPTS) to obtain modified nanocrystalline cellulose (M-NCC) crosslinker and used during free radical polymerization of thermosensitive N-isopropyl acrylamide (NIPA) monomer to synthesize NIPA/M-NCC hydrogel. The resulting nanocomposite hydrogels exhibit superior mechanical, thermal, and temperature-responsive swelling properties compared to conventional hydrogels prepared with traditional bi-functional N, N′-methylene bis (acrylamide) (MBA) as a crosslinker. The elongation at break, tensile strength, and toughness of the NIPA/M-NCC hydrogels significantly increase and Young’s modulus decrease than conventional hydrogel. The designed M-NCC crosslinker could be utilized to improve the mechanical strength of any polymeric elastomer or hydrogel systems produced through chain polymerization.

Application of a Radiopaque Viscous Hydrogel Spacer for Prostate Cancer Radiation Therapy: A Prospective Phase 2 Study

The aim of this study was to evaluate the application of a radiopaque viscous spacer (RVS) for prostate cancer radiation therapy (RT), including injection procedure, toxicity, treatment planning, image guidance, and imaging results up to 12 months after RT. RVS (median, 10 mL) was injected between prostate and rectal wall in 30 patients. Cone beam computed tomography (CT) was performed during the course of RT, a magnetic resonance imaging 3 and 12 months after RT. Injection and treatment tolerability were analyzed. The resulting distribution was compared with a control group of 30 patients with an initially fluid spacer. Procedure- or device-related adverse events were not observed. Signs of hydrogel migration were not found in any case. The volume decreased by 25% at 3 months after RT, and small residues were detected at 12 months after RT in 3 cases (10%). The median rectal volume percentage within the 90% isodose was 3.0% (interquartile range, 1.5%-4.5%). Acute and late gastrointestinal toxicities were found in 17% and 3%, respectively (all grade 1). The median distance between prostate and rectum at the base/midplane/apex was greater for RVS in comparison to initially fluid spacer (14/12/11 mm vs 12/10/10 mm, respectively), the gel symmetry (right vs left from midline) was comparable. The application was assessed to be easier to control by the users, and visibility in cone beam CT as good. The injection of a radiopaque viscous hydrogel spacer resulted in a prostate-rectum distance of >10 mm in most cases. The resulting rectum volume within the high-dose region and RT toxicity were very low. Advantages in comparison to the conventional hydrogel spacer are predominantly an improved placement control during the injection process and good visibility on CT.

Ultra-stretchable and conductive polyacrylamide/carboxymethyl chitosan composite hydrogels with low modulus and fast self-recoverability as flexible strain sensors

There is a great demand for the fabrication of soft electronics using hydrogels due to their biomimetic structures and good flexibility. However, conventional hydrogels have poor mechanical properties, which restricts their applications as stretchable sensors. Herein, a facile one-step strategy is proposed to fabricate tough and conductive hydrogels by making use of the graftability of carboxymethyl chitosan without extra conductive matter and crosslinking agent. The obtained polyacrylamide/carboxymethyl chitosan composite hydrogels possess outstanding transmittance and excellent mechanical performances, with tensile breaking stress of 630 kPa, breaking strain of 4560 %, toughness of 8490 kJ/m3. These hydrogels have low modulus of 5–20 kPa, fast recoverability after unloading, high conductivity of ∼0.85 S/m without the addition of other conductive substances and good biocompatibility. The ionic conductivity of the gels originates from the counterions of carboxymethyl chitosan, affording the hydrogels as resistive-type sensors. The resultant hydrogel sensors demonstrate a broad strain window (0.12–1500 %), excellent linear response, high sensitivity with the gauge factor reaching 11.72, and great durability, capable of monitoring diverse human motions. This work provides a new strategy to develop stretchable conductive hydrogels with promising applications in the fields of artificial intelligence and flexible electronics.

Magnetic hydrogel applications in articular cartilage tissue engineering.

Articular cartilage defects afflict millions of individuals worldwide, presenting a significant challenge due to the tissue's limited self-repair capability and anisotropic nature. Hydrogel-based biomaterials have emerged as promising candidates for scaffold production in artificial cartilage construction, owing to their water-rich composition, biocompatibility, and tunable properties. Nevertheless, conventional hydrogels typically lack the anisotropic structure inherent to natural cartilage, impeding their clinical and preclinical applications. Recent advancements in tissue engineering (TE) have introduced magnetically responsive hydrogels, a type of intelligent hydrogel that can be remotely controlled using an external magnetic field. These innovative materials offer a means to create the desired anisotropic architecture required for successful cartilage TE. In this review, we first explore conventional techniques employed for cartilage repair and subsequently delve into recent breakthroughs in the application and utilization of magnetic hydrogels across various aspects of articular cartilage TE.

Polydopamine functionalized stellate mesoporous silica using mussel inspired chemistry for ultrastretchable, conductive and self-healing hydrogel on wearable strain sensors

Conductive hydrogels hold great promise in wearable strain sensor for human motion detection. Nevertheless, the poor mechanical properties, inferior sensitivity and the deficiency of multifunctionalities of conventional hydrogels tremendously constrain their applications. Herein, inspired by mussel chemistry, polydopamine (PDA) and Au nanoparticles (Au NPs) were used to modify stellate mesoporous silica (STMS), which could provide conductivity and multiple non-covalent interactions. The synthesized STMS@PDA-Au NPs were further used to prepare composite polyacrylic acid (PAA) hydrogel (STMS@PDA-Au NPs/PAA) by a one-pot strategy for the application of motion sensors. The resulting hydrogel exhibited satisfactory stretchability (663%), remarkable tensile strength (2.18 MPa), high sensitivity (Gauge Factor = 2.86) and distinguished self-healing properties (90.8%), which are believed to be contributed by the existence of coordination complexations and multiple hydrogen-bonding interactions in the hydrogel network. Additionally, with a rapid dynamic response time (180 ms) and fatigue resistance, this work provides useful insights as a wearable sensor for epidermal sensing applications.

Synthesis of a polyacrylamide hydrogel modified with a reactive carbamate surfactant: Characterization, swelling behavior, and mathematical models

Hydrogels are polymeric materials that can absorb and retain large amounts of water. They have various applications in agriculture, horticulture, oil recovery, and water management. However, conventional hydrogels have limited swelling (Q), equilibrium swelling (Q∞), and water retention capacities (DQ) under different environmental conditions. In this study, we synthesized a series of hydrophobically associated hydrogels by the aqueous polymerization of acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and a novel amphiphilic hydrophobic monomer (RCS-10). Further, we investigated the effects of the RCS-10 content on Q, the mechanical properties, and water retention capacity (DQ) of the hydrogels. We also examined the influence of temperature, pH, salt type and concentration, and urea concentration on Q, finding that an increase in the RCS-10 content decreased Q and increased the DQ of the hydrogels. The hydrogels exhibited high Q in distilled water, low-salt solutions, and low-urea (1 wt%) solutions. In the latter, the Q∞ was as high as 768.99 g/g. The hydrogels also showed excellent cyclic swelling performance and maintained high Q∞ (759.99 g/g) after six cycles. Crucially, the hydrophobic association hydrogels demonstrated superior swelling and water retention properties compared to conventional hydrogels. Thus, the hydrogels have applications in water management in various fields including agriculture and horticulture.

Reinforcing Hydrogel by Nonsolvent-Quenching Facilitated In-Situ Nanofibrosis.

Nanofibrous hydrogels are pervasive in load-bearing soft tissues, which are believed to be key to their extraordinary mechanical properties. Enlighted by this phenomenon, a novel reinforcing strategy for polymeric hydrogels is proposed, where polymer segments in the hydrogels are induced to form nanofibers in-situ by bolstering their controllable aggregation on the nanoscale level. Polyvinyl alcohol hydrogels are chosen to demonstrate the virtue of this strategy. A nonsolvent-quenching step is introduced into the conventional solvent-exchange hydrogel preparation approach, which readily promotes the formation of nanofibrous hydrogels in the following solvent-tempering process. The resultant nanofibrous hydrogels demonstrate significantly improved mechanical properties and swelling resistance, compared to the conventional solvent-exchange hydrogels with identical compositions. This work validates the hypothesis that bundling polymer chains to form nanofibers can lead to nanofibrous hydrogels with remarkably enhanced mechanical performances, which may open a new horizon for single-component hydrogel reinforcement. This article is protected by copyright. All rights reserved.

Rapid and Controllable Preparation of Multifunctional Lignin-Based Eutectogels for the Design of High-Performance Flexible Sensors.

Currently, there is a limited amount of research on PEDOT:LS (poly(3,4-ethylenedioxythiophene):sulfonated lignin)-based hydrogels. While the addition of PEDOT:LS can enhance the conductivity of the gel, it unavoidably disrupts the gel network and negatively affects its mechanical properties. The preparation process and freezing resistance of the hydrogels also pose significant challenges for their practical applications. In this study, we have developed a novel self-catalytic system, PEDOT:LS-Fe3+, for the rapid fabrication of conductive hydrogels. These hydrogels are further transformed into eutectogels by immersing them in a deep eutectic solvent. Compared with conventional hydrogels, the eutectogels exhibit improved elongation, mechanical strength, and resistance to freezing. Specifically, the eutectogels containing 2 wt % PEDOT:LS as conductive fillers and catalysts demonstrate exceptional stretchability (∼460%), self-adhesion (∼14.6 kPa on paper), UV-blocking capability (∼99.9%), and ionic conductivity (∼1.2 mS cm-1) even at extremely low temperatures (-60 °C). Moreover, the eutectogels exhibit high stability and sensitivity in flexible sensing, successfully detecting various human motions. This study presents a novel approach for the rapid preparation of the hydrogels by utilizing lignin in the conductive PEDOT polymerization process and forming a self-catalytic system with metal ions. These advancements make the eutectogels a promising candidate material for flexible wearable electronics.