Natural Glycyrrhizic Acid-Tailored Homogeneous Conductive Polyaniline Hydrogel as a Flexible Strain Sensor

Bioactive glycyrrhizic acid-astragalus polysaccharide hydrogel facilitates gastric ulcer healing via ROS scavenging and anti-apoptotic effects

Gastric ulcers are refractory wounds that pose a significant clinical challenge, underscoring the urgent need for effective and affordable therapeutic strategies. In this study, we purified a novel homogeneous astragalus polysaccharide (APS13) and elucidated its structure, which consists of a →4)-α-1,4-Glc(1→ backbone with glucose branches at the 6-position, as determined by 2D-NMR and glycosyl residue analysis. To enhance its tissue adhesion and drug release profile, APS13 was co-assembled with glycyrrhizic acid (GA) into a GA-APS hydrogel. The resulting hydrogel exhibited strong adhesion and prolonged gastric retention under acidic conditions. In vivo and in vitro studies demonstrated that the GA-APS hydrogel reduced ulcer area, improved mucosal integrity, and decreased apoptosis-related protein expression in a rat model of acute gastric ulcer. Comparative analyses showed enhanced therapeutic outcomes relative to treatment with GA or APS13 alone. Proteomic and cellular experiments further indicated that the hydrogel's protective effect is associated with attenuation of ROS-induced apoptosis. These findings highlight the therapeutic potential of APS13-based hydrogels and offer a natural-material strategy for addressing oxidative stress-related gastric injury.

Double-layer biodegradable hydrogel based on tragacanth gum as an electrically conductive nanoplatform for TENS device application

This research focuses on designing and creating a double-layer bio-hydrogel made from tragacanth gum (TG) and carboxylated graphene (GrF), coated with polyaniline (PANI) for transcutaneous electrical nerve stimulation (TENS) devices. X-ray diffraction (XRD) analysis showed that the PANI coating removed peaks associated with crystalline regions (13.99° and 16.87°) in the tragacanth gum/polyvinyl alcohol/carboxylated graphene (TPG) bio-hydrogel. This indicates strong interactions between the PANI layer and the TPG bio-hydrogel matrix, with reduced crystallinity due to structural changes. Conductivity tests revealed significant improvements from both GrF and the PANI coating. At low frequencies (80 Hz), the PANI coating increased the alternating current conductivity of the tragacanth gum/polyvinyl alcohol (TP) bio-hydrogel by 20,481 times and that of the TPG bio-hydrogel by 1804 times. Contact angle measurements indicated a low hydrophilic surface (61.4°), thanks to the GrF and PANI coating. FESEM analysis confirmed the uniform distribution of GrF within the bio-hydrogel and revealed two distinct shapes in the PANI coating, indicating improved structural integrity and functionality. Mechanical tests showed a 4.59-fold increase in tensile strength, improving durability. MTT assays confirmed biocompatibility (>90.37 % cell viability), and the bio-hydrogel biodegraded completely within two months.

Highly stretchable, self-healing, antibacterial, conductive, and amylopectin-enhanced hydrogels with gallium droplets loading as strain sensors

In this study, we address the challenge of developing highly conductive hydrogels with enhanced stretchability for use in wearable sensors, which are critical for the precise detection of human motion and subtle physiological strains. Our novel approach utilizes amylopectin, a biopolymer, for the uniform integration of liquid metal gallium into the hydrogel matrix. This integration results in a conductive hydrogel characterized by remarkable elasticity (up to 7100 % extensibility) and superior electrical conductance (Gauge Factor = 31.4), coupled with a minimal detection limit of less than 0.1 % and exceptional durability over 5000 cycles. The hydrogel demonstrates significant antibacterial activity, inhibiting microbial growth in moist environments, thus enhancing its applicability in medical settings. Employing a synthesis process that involves ambient condition polymerization of acrylic acid, facilitated by a hydrophobic associative framework, this hydrogel stands out for its rapid gelation and robust mechanical properties. The potential applications of this hydrogel extend beyond wearable sensors, promising advancements in human-computer interaction through technologies like wireless actuation of robotic systems. This study not only introduces a viable material for current wearable technologies but also sets a foundation for future innovations in bio-compatible sensors and interactive devices.

Conducting polymer hydrogels based on supramolecular strategies for wearable sensors

Conductive polymer hydrogels (CPHs) are gaining considerable attention in developing wearable electronics due to their unique combination of high conductivity and softness. However, in the absence of interactions, the incompatibility between hydrophobic conductive polymers (CPs) and hydrophilic polymer networks gives rise to inadequate bonding between CPs and hydrogel matrices, thereby significantly impairing the mechanical and electrical properties of CPHs and constraining their utility in wearable electronic sensors. Therefore, to endow CPHs with good performance, it is necessary to ensure a stable and robust combination between the hydrogel network and CPs. Encouragingly, recent research has demonstrated that incorporating supramolecular interactions into CPHs enhances the polymer network interaction, improving overall CPH performance. However, a comprehensive review focusing on supramolecular CPH (SCPH) for wearable sensing applications is currently lacking. This review provides a summary of the typical supramolecular strategies employed in the development of high-performance CPHs and elucidates the properties of SCPHs that are closely associated with wearable sensors. Moreover, the review discusses the fabrication methods and classification of SCPH sensors, while also exploring the latest application scenarios for SCPH wearable sensors. Finally, it discusses the challenges of SCPH sensors and offers suggestions for future advancements.

Dual design strategy for carboxymethyl cellulose-polyaniline composite hydrogels as super-sensitive amphibious sensors

Conductive hydrogels as ideal candidate materials for flexible sensors have exhibited many promising applications. However, complex application environments, such as low temperatures or underwater conditions, have introduced new requirements for hydrogel sensors. Herein, a high-performance conductive hydrogel based on carboxymethyl cellulose-polyaniline (CMC-PANI) submicron spheres, poly (vinyl alcohol) (PVA) and phytic acid (PA) was designed and fabricated via a dual design strategy. CMC-PANI particles were introduced to not only empower the good electromechanical performance to the hydrogels, but also enhance the mechanical properties. The obtained hydrogel exhibited good mechanical property, anti-freezing, anti-swellable behavior and recyclable performance. Resistive-type strain sensors assembled by the prepared hydrogels exhibited high pressure sensitivity (34.17×10-2 kPa-1) and fast response time (100 ms), which can clearly detect the pulse beats. Moreover, the hydrogel sensors can achieve long-term stability, high sensitivity and fatigue resistance as an underwater sensor. Based on these favorable performances, the conductive polymer hydrogels may open up an enticing avenue for functional soft materials in health diagnostic and electronic components.

Facile One-Pot Preparation of Polypyrrole-Incorporated Conductive Hydrogels for Human Motion Sensing

Conductive hydrogels have been widely used in soft robotics, as well as skin-attached and implantable bioelectronic devices. Among the candidates of conductive fillers, conductive polymers have become popular due to their intrinsic conductivity, high biocompatibility, and mechanical flexibility. However, it is still a challenge to construct conductive polymer-incorporated hydrogels with a good performance using a facile method. Herein, we present a simple method for the one-pot preparation of conductive polymer-incorporated hydrogels involving rapid photocuring of the hydrogel template followed by slow in situ polymerization of pyrrole. Due to the use of a milder oxidant, hydrogen peroxide, for polypyrrole synthesis, the photocuring of the hydrogel template and the growing of polypyrrole proceeded in an orderly manner, making it possible to prepare conductive polymer-incorporated hydrogels in one pot. The preparation process is facile and extensible. Moreover, the obtained hydrogels exhibit a series of properties suitable for biomedical strain sensors, including good conductivity (2.49 mS/cm), high stretchability (>200%), and a low Young's modulus (~30 kPa) that is compatible with human skin.

A natural food-grade supramolecular self-assembly system for creation of hierarchically structured hydrogels

We develop a novel hierarchically structured hydrogel by the supramolecular self-assembly of all-natural food-grade building blocks, glycyrrhizic acid (GA) and carrageenan (CG). The co-assembled GA-CG hydrogel system displays an unusual structural transition with the appearance from opacity to translucence and then to opacity, as a function of the concentration of metal ions. The unique GA-CG supramolecular hydrogel system can serve as solid, edible, and responsive active cargo delivery platforms for food and biomedical applications.

Synergistic Antimicrobial Glycyrrhizic Acid-Based Functional Biosensing Composite for Sensitive Glucose Monitoring and Collaborative Wound Healing

High glucose blood and bacterial infection remain major issues for the slow healing of diabetic wounds, so developing functional biosensing composite with excellent antibacterial and remarkable glucose response sensitivity is necessary and prospective. Herein, by in situ synthesis AgNPs on the surface of self-prepared PTIGA elastomers, PTIGA-AgNPs conductive composites are obtained with efficient synergistic antibacterial effect, excellent mechanical and self-healing properties. The strain of the composites can reach 1800%, and its self-healing efficiency exceeds 90% at 60 °C within 8 h. Both elastomers and composites represent excellent biocompatibility and the antibacterial rate against E. coli and S. aureus exceeded 90%. Moreover, the biosensor assembled from the conductive composites exhibits excellent glucose response sensitivity and stability, with a sensitivity coefficient of 0.518 mA mm-1 in the range of 0.2-3.6 × 10-3 m glucose concentration, as well as a low detection limit of 0.08 × 10-3 m. Furthermore, based on the remarkable antibacterial performance and bioactivity derived from GA, the composites reduce the expression of pro-inflammatory factors and promote the production of anti-inflammatory factors, and effectively promote the regeneration of skin and granulation tissue of wounds in a diabetic full-thickness skin defect model, demonstrating the enormous therapeutic potential in diabetic wound healing.

Controllable proton-reservoir ordered gel towards reversible switching and reliable electromagnetic interference shielding

Smart and dynamic electromagnetic interference (EMI) shielding materials possess a remarkable capacity to modify their EMI shielding abilities, rendering them invaluable in various civil and military applications. However, the present response mechanism of switch-type EMI shielding materials is slightly restricted, as it primarily depends on continuous pressure induction, thereby resulting in concerns regarding their durability and reliability. Herein, for the first time, we demonstrate a novel method for achieving solvent-responsive, reversible switching, and robust EMI shielding capabilities using a controlled proton-reservoir ordered gel. The gel contains polyaniline (PANI) and sodium alginate (SA). Initially, SA acts as a proton reservoir for PANI in an aqueous system, enhancing the doping level of PANI and improving its electrical conductivity. Additionally, PANI and SA chains respond to diverse polar solvents, such as water, acetonitrile, ethanol, n-hexane, and air, inducing distinct conformations that affect the degree of PANI conjugation and electron migration along the chains. This process is reversible and non-destructive to the polymer chain, ensuring the effective and uncompromised performance of the EMI shielding switch. We can achieve precise and reversible tuning (on/off) of EMI shielding with different effectiveness levels by manipulating the solvents within the framework. This work opens a new solvent-stimuli avenue for the development of EMI shielding materials with reliable and intelligent on/off switching capabilities.

Recent advances in 3D printable conductive hydrogel inks for neural engineering

Recently, the 3D printing of conductive hydrogels has undergone remarkable advances in the fabrication of complex and functional structures. In the field of neural engineering, an increasing number of reports have been published on tissue engineering and bioelectronic approaches over the last few years. The convergence of 3D printing methods and electrically conducting hydrogels may create new clinical and therapeutic possibilities for precision regenerative medicine and implants. In this review, we summarize (i) advancements in preparation strategies for conductive materials, (ii) various printing techniques enabling the fabrication of electroconductive hydrogels, (iii) the required physicochemical properties of the printed constructs, (iv) their applications in bioelectronics and tissue regeneration for neural engineering, and (v) unconventional approaches and outlooks for the 3D printing of conductive hydrogels. This review provides technical insights into 3D printable conductive hydrogels and encompasses recent developments, specifically over the last few years of research in the neural engineering field.

Bio-Inspired Homogeneous Conductive Hydrogel with Flexibility and Adhesiveness for Information Transmission and Sign Language Recognition

The wearable electronic technique is increasingly becoming an effective approach to overcoming the communication obstacles between signers and non-signers. However, the efficacy of conducting hydrogels currently proposed as flexible sensor devices is hindered by their poor processability and matrix mismatch, which frequently results in adhesion failure at the combined interfaces and deterioration of mechanical and electrochemical performance. Herein, we propose a hydrogel composed of a rigid matrix in which the hydrophobic and aggregated polyaniline was homogeneously embedded, while quaternate-functionalized nucleobase moieties endowed the flexible network with adhesiveness. Accordingly, the resulting hydrogel with chitosan-graft-polyaniline (chi-g-PANI) copolymers exhibited a promising conductivity (4.8 S·m^-1) because of the uniformly dispersed polyaniline components and a high strain strength (0.84 MPa) because of the chain entanglement of chitosan after soaking. In addition, the modified adenine molecules not only realized synchronization in improving the stretchability (up to 1303%) and exhibiting a skin-like elastic modulus (≈184 kPa), but also provided a durable interfacial contact with various materials. The hydrogel was further fabricated into a strain-monitoring sensor for information encryption and sign language transmission based on its sensing stability and strain sensitivity of up to 2.77. The developed wearable sign language interpreting system provides an innovative strategy to assist auditory or speech-impaired people in communicating with non-signers using visual-gestural patterns including body movements and facial expressions.