The development of facile and versatile strategies with low-cost for hydrogel construction is of tremendous scientific interest. Herein, we demonstrate that naturally derived, cost-effective tannic acid (TA) can be an efficient gelation binder for the hydrogel formation with a series of commercially available water-soluble polymers. With a five-polyphenol-arm structure, TA molecules are able to grasp polymer chains through either hydrogen or ionic bonds and cross-link them together by coordinate bonds in the presence of Fe(III) ions. These two interactions can be elegantly balanced by tuning the weight ratios of polymer/TA and TA/ Fe 3+ , which is the key point for the construction of supramolecular hydrogels. The supramolecular hydrogels exhibit multiple functionalities including mechanical tenability, rapid self-healing, pH-stimuli responsiveness, and free radical scavenging abilities. TA as a dynamic and versatile catechol group modifier provides a simple path to the construction of multifunctional hydrogels, which shows obvious advantages such as easy and green processing, low cost, and large-scale preparation.

Medical sealant devices for in vivo hemostasis are far from satisfactory in the aged society. A major challenge is effective integration of quick hemorrhage control of the increased anticoagulated patients, high safety, and facile accessibility. Here, a well‐defined ammonolysis‐based Tetra‐PEG hydrogel sealant is developed with rapid gelation speed, strong tissue adhesion, and high mechanical strength. Introduction of cyclized succinyl ester groups into a hydrogel matrix endows the sealant with fast degradable and controllably dissolvable properties. The hydrogel possesses outstanding hemostatic capabilities even under the anticoagulated conditions while displaying excellent biocompatibility and feasibility. These results reveal that the optimized hydrogel may be a facile, effective, and safe sealant for hemorrhage control in vivo.

Immediate hemorrhage control and infection prevention are pivotal for saving lives in critical situations such as battlefields, natural disasters, traffic accidents, and so on. In situ hydrogels are promising candidates, but their mechanical strength is often not strong enough for use in critical situations. In this study, we constructed three hydrogels with different amounts of Schiff-base moieties from 4-arm-PEG-NH2, 4-arm-PEG-NHS, and 4-arm-PEG-CHO in which vancomycin was incorporated as an antimicrobial agent. The hydrogels possess porous structures, excellent mechanical strength, and high swelling ratio. The cytotoxicity studies indicated that the composite hydrogel systems possess good biocompatibility. The Schiff bases incorporated improve the adhesiveness and endow the hydrogels with bacteria-sensitivity. The in vivo hemostatic and antimicrobial experiments on rabbits and pigs demonstrated that the hydrogels are able to aid in rapid hemorrhage control and infection prevention. In summary, vancomycin-loaded hydrogels may be excellent candidates as hemostatic and antibacterial materials for first aid treatment of the wounded in critical situations.

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Hydrogels are required to have high mechanical properties, biocompatibility, and an easy fabrication process for biomedical applications. Double-network hydrogels, although strong, are limited because of the complicated preparation steps and toxic materials involved. In this study, we report a simple method to prepare tough, in situ forming polyethylene glycol (PEG)-agarose double-network (PEG-agarose DN) hydrogels with good biocompatibility. The hydrogels display excellent mechanical strength. Because of the easily in situ forming method, the resulting hydrogels can be molded into any form as needed. In vitro and in vivo experiments illustrate that the hydrogels exhibit satisfactory biocompatibility, and cells can attach and spread on the hydrogels. Furthermore, the residual amino groups in the network can also be functionalized for various biomedical applications in tissue engineering and cell research.

Here we demonstrate a type of pH and reduction dual-sensitive biodegradable micelles, which were self-assembled by a cationic polymer in an aqueous solution. Due to tumor cells or tissues showing low pH and high reduction concentration, these micelles possessed specific tumor targetability and maximal drug-release controllability inside tumor cells upon changes in physical and chemical environments, but presented good stability at physiological conditions. CCK-8 assay showed that the DOX-loaded micelles had a similar cytotoxicity for MCF-7 tumor cells as free DOX, and blank micelles had a very low cytotoxicity to the cells. Fluorescent microscopy observation revealed that the drug-loaded micelles could be quickly internalized by endosomes to inhibit cancer cell growth. These results indicated these biodegradable micelles, as a novel and effective pH- and redox-responsive nanocarrier, have a potential to improve drug delivery and enhance the antitumor efficacy.

Designing versatile functional medical adhesives with injectability, selfhealing, and strong adhesion is of great significance to achieve desirable therapeutic effects for promoting wound sealing in healthcare. Herein, a self-healing injectable adhesive is fabricated by physical interaction of polyphenol compound tannic acid (TA) and eight-arm poly(ethylene glycol) end-capped with succinimide glutarate active ester (PEG-SG). The hydrogen bonding induced from the structural unit (−CH 2 −CH 2 −O−) of PEG and catechol hydroxyl (−OH) of TA, accompanied by ester exchange between Nhydroxysuccinimide (−NHS) and amino (−NH 2 ) of proteins, contributes to self-healing ability and rapid strong adhesion. Notably, the PEG/TA adhesive can repeatedly adhere to rigid porcine tissues, close the coronary artery under a large incision tension, and bear a heavy load of 2 kg. By exhibiting shear-thinning and anti-swelling properties, the PEG/TA adhesive can be easily applied through single-syringe extrusion onto various wounds. The single-channel toothpaste-like feature of the adhesive ensures its storage hermetically for portable usage. Moreover, in vivo operation and histological H&E staining results indicate that the PEG/TA adhesive greatly accelerates wound healing and tissue regeneration in a rat model. With the specialty of injectability, instant self-healing, and long-lasting strong adhesion to facilitate excellent therapeutic effects, the multifunctional PEG/ TA adhesive may provide a new alternative for self-rescue and surgical situations.

The hydrogel patches with embedded microcapsules could achieve ultrasound responsive and enhanced transdermal delivery of diclofenac sodium.