Zwitterionic hydrogels exhibit eminent nonfouling and hemocompatibility. Several key challenges hinder their application as coating materials for blood-contacting biomedical devices, including weak mechanical strength and low adhesion to the substrate. Here, we report a poly(carboxybetaine) microgel reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel with excellent mechanical robustness and anti-swelling properties. The pCBM/pSB hydrogel coating was bonded to the PVC substrate via the entanglement network between the pSB and PVC chain. Moreover, the pCBM/pSB hydrogel coating can maintain favorable stability even after 21 d PBS shearing, 0.5 h strong water flushing, 1000 underwater bends, and 100 sandpaper abrasions. Notably, the pCBM/pSB hydrogel coated PVC tubing can not only mitigate the foreign body response but also prevent thrombus formation ex vivo in rats and rabbits blood circulation without anticoagulants. This work provides new insights to guide the design of pure zwitterionic hydrogel coatings for biomedical devices.

Strong mechanical performance, appropriate adhesion capacity, and excellent biocompatibility of conductive hydrogel-based sensors are of great significance for their application. However, conventional conductive hydrogels usually exhibit insufficient mechanical strength and adhesion. In addition, they will lose flexibility and conductivity under subzero temperature and a dry environment owing to inevitable freezing and evaporation of water. In this study, a tough, flexible, self-adhesive, long-term moisturizing, and antifreezing organohydrogel was prepared, which was composed of gelatin, zwitterionic poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (PSBMA), MXene nanosheets, and glycerol. Natural gelatin was incorporated to enhance mechanical performance via the entanglement of a physical cross-linked network and a PSBMA network, which was also used as a stabilizer to disperse MXene into the organohydrogel. Zwitterionic PSBMA endowed the organohydrogel with good adhesion and self-healing properties. Long-term moisturizing properties and antifreeze tolerance could be achieved owing to the synergistic water retention capacity of PSBMA and glycerol. The resulting PSBMA–gelatin–MXene–glycerol (PGMG) organohydrogel exhibited high mechanical fracture strength (0.65 MPa) and stretchability (over 1000%), excellent toughness (3.87 MJ/m3), strong and repeated adhesion to diverse substrates (e.g., paper, glass, silicon rubber, iron, and pig skin), good fatigue resistance (under the cyclic stretching–releasing process), and rapid recovery capacity. Moreover, the PGMG organohydrogel showed good stability under −40 °C. The sensor based on PGMG organohydrogel could tightly attach to the human skin and real-time-monitor the motions of joints (e.g., bending of the finger, wrist, elbow, and knee) and the change in mood such as smiling and frowning. Therefore, PGMG organohydrogels have a huge potential for wearable sensors under room temperature or extreme environments.

Underwater adhesion plays an essential role in soft electronics for the underwater interface. Although hydrogel-based electronics are of great interest, because of their versatility, water molecules prevent hydrogels from adhering to substrates, thus bottlenecking further applications. Herein, inspired by the barnacle proteins, MXene/PHMP hydrogels with strong repeatable underwater adhesion are developed through the random copolymerization of 2-phenoxyethyl acrylate, 2-methoxyethyl acrylate, and N-(2-hydroxyethyl) acrylamide with the presence of MXene nanosheets. The hydrogels are mechanically tough (elastic modulus of 32 kPa, fracture stress of 0.11 MPa), and 2-phenoxyethyl acrylate (PEA) with aromatic groups endows the hydrogel with nonswelling property and prevents water molecules from invading the adhesive interface, rendering the hydrogels an outstanding adhesive behavior toward various substrates (including glass, iron, polyethylene terephthalate (PET), porcine). Besides, dynamic physical interactions allow for instant and repeatable underwater adhesion. Furthermore, the MXene/PHMP hydrogels exhibit a high conductivity (0.016 S/m), fast responsiveness, and superior sensitivity as a strain sensor (gauge factor = 7.17 at 200%–500% strain) and pressure sensor (0.63 kPa–1 at 0–70 kPa). The underwater applications of bionic hydrogel-based sensors have been demonstrated, such as human motion, pressure sensing, and holding objects. It is anticipated that the instant and repeatable underwater adhesive hydrogel-based sensors extend the underwater applications of hydrogel electronics.

Currently, although conducting polymers have exhibited potential electrophysiological modulation, designing bioinspired ultra‐histocompatible conducting polymers remains a long‐standing challenge. Moreover, the water dispersibility, conductivity, and biocompatibility of conducting polymers are incompatible, which restricts their application in tissue engineering. Herein, a multilevel template dispersion strategy is presented to produce poly(3,4‐ethylenedioxythiophene):(dextran sulfate/carboxymethyl chitosan) (PEDOT:(DSS/CMCS)) with biocompatibility superior to that of commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) without sacrificing processability and conductivity. The PEDOT:(DSS/CMCS) and oxidized dextran solutions form an injectable PEDOT‐based hydrogel (PDCOH) mediated by dynamic covalent imine bonds under mild conditions. The PDCOH has a tissue‐matched modulus and conductivity to adapt to the mechanical environment of dynamic tissue and modulate fibrosis‐induced electrical decoupling. The PDCOH combined with adipose‐derived stem cells demonstrates superior cardiac repair effects over cell suspensions and nonconductive hydrogels, inhibiting ventricular remodeling, reducing fibrous scarring, promoting vascular regeneration, and restoring electrophysiological and pulsatile functions.

Although hydrogel-based patches have shown promising therapeutic efficacy in myocardial infarction (MI), synergistic mechanical, electrical, and biological cues are required to restore cardiac electrical conduction and diastolic–systolic function. Here, an injectable mechanical–electrical coupling hydrogel patch (MEHP) is developed via dynamic covalent/noncovalent cross-linking, appropriate for cell encapsulation and minimally invasive implantation into the pericardial cavity. Pericardial fixation and hydrogel self-adhesiveness properties enable the MEHP to highly compliant interfacial coupling with cyclically deformed myocardium. The self-adaptive MEHP inhibits ventricular dilation while assisting cardiac pulsatile function. The MEHP with the electrical conductivity and sensitivity to match myocardial tissue improves electrical connectivity between healthy and infarcted areas and increases electrical conduction velocity and synchronization. Overall, the MEHP combined with cell therapy effectively prevents ventricular fibrosis and remodeling, promotes neovascularization, and restores electrical propagation and synchronized pulsation, facilitating the clinical translation of cardiac tissue engineering.