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Fabrication of versatile hydrogels in a facile and effective manner represents a pivotal challenge in the field of biomaterials. Herein, a novel strategy is presented for preparing on-demand degradable hydrogels with multilevel responsiveness. By employing selenol-dichlorotetrazine nucleophilic aromatic substitution (S N Ar) to synthesize hydrogels under mild conditions in a buffer solution, the necessity of additives or posttreatments can be obviated. The nucleophilic and redox reactions between selenol and tetrazine culminate in the formation of three degradable chemical bonds-diselenide, aryl selenide, and dearomatized selenide-in a single, expeditious step. The resultant hydrogel manifests exceptional adaptability to intricate environments in conjunction with self-healing and on-demand degradation properties. Furthermore, the resulting material demonstrated light-triggered antibacterial activity. Animal studies further underscore the potential of integrating metformin into Se-Tz hydrogels under green light irradiation, as it effectively stimulates angiogenesis and collagen deposition, thereby fostering efficient wound healing. In comparison to previously documented hydrogels, Se-Tz hydrogels exhibit controlled degradation and drug release, outstanding antibacterial activity, mechanical robustness, and bioactivity, all without the need for costly and intricate preparation procedures. These findings underscore Se-Tz hydrogels as a safe and effective therapeutic option for diabetic wound dressings., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Geriatric diseases are a group of diseases with unique characteristics related to senility. With the rising trend of global aging, senile diseases now mainly include endocrine, cardiovascular, neurodegenerative, skeletal, and muscular diseases and cancer. Compared with younger populations, the structure and function of various cells, tissues and organs in the body of the elderly undergo a decline as they age, rendering them more susceptible to external factors and diseases, leading to serious tissue damage. Tissue damage presents a significant obstacle to the overall health and well-being of older adults, exerting a profound impact on their quality of life. Moreover, this phenomenon places an immense burden on families, society, and the healthcare system.In recent years, stem cell-derived exosomes have become a hot topic in tissue repair research. The combination of these exosomes with biomaterials allows for the preservation of their biological activity, leading to a significant improvement in their therapeutic efficacy. Among the numerous biomaterial options available, hydrogels stand out as promising candidates for loading exosomes, owing to their exceptional properties. Due to the lack of a comprehensive review on the subject matter, this review comprehensively summarizes the application and progress of combining stem cell-derived exosomes and hydrogels in promoting tissue damage repair in geriatric diseases. In addition, the challenges encountered in the field and potential prospects are presented for future advancements., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Shi et al.)

Fabrication of versatile hydrogels in a facile and effective manner represents a pivotal challenge in the field of biomaterials. Herein, a novel strategy is presented for preparing on‐demand degradable hydrogels with multilevel responsiveness. By employing selenol‐dichlorotetrazine nucleophilic aromatic substitution (SNAr) to synthesize hydrogels under mild conditions in a buffer solution, the necessity of additives or posttreatments can be obviated. The nucleophilic and redox reactions between selenol and tetrazine culminate in the formation of three degradable chemical bonds—diselenide, aryl selenide, and dearomatized selenide—in a single, expeditious step. The resultant hydrogel manifests exceptional adaptability to intricate environments in conjunction with self‐healing and on‐demand degradation properties. Furthermore, the resulting material demonstrated light‐triggered antibacterial activity. Animal studies further underscore the potential of integrating metformin into Se‐Tz hydrogels under green light irradiation, as it effectively stimulates angiogenesis and collagen deposition, thereby fostering efficient wound healing. In comparison to previously documented hydrogels, Se‐Tz hydrogels exhibit controlled degradation and drug release, outstanding antibacterial activity, mechanical robustness, and bioactivity, all without the need for costly and intricate preparation procedures. These findings underscore Se‐Tz hydrogels as a safe and effective therapeutic option for diabetic wound dressings. [ABSTRACT FROM AUTHOR]

Conductive hydrogels can be utilized in the field of flexible supercapacitors due to their stretchable properties and high ionic conductivity. However, many of the conductive hydrogels lose their stretchability and conductivity at subzero temperatures. Herein, a novel Janus POSS‐based hydrogel electrolyte that shows excellent flexibility and ionic conductivity at low temperatures is designed and prepared by the copolymerization of acrylamide and a water‐soluble Janus‐type polyhedral oligomeric silsesquioxane (AS‐POSS) containing sodium sulfonate groups and double bonding groups. The sodium sulfonate groups of AS‐POSS and LiCl endow the hydrogel electrolyte with excellent anti‐freezing ability. Simultaneously, the double bonding groups of AS‐POSS enable a successful POSS crosslinking in the polymer network, resulting in a highly stretchable hydrogel electrolyte (1445%) with high ionic conductivity (0.067 S cm−1) at −20°C. Thereafter, the all‐in‐one flexible supercapacitor is prepared by in‐situ polymerization of aniline. Based on the exceptional anti‐freezing properties of the Janus POSS‐based hydrogel electrolyte, the all‐in‐one supercapacitor exhibits stable electrochemical performance (>90% capacitance retained under deformation at −20°C) and excellent cycling stability (only 19.7% capacitance decay over 2000 charge/discharge cycles at −20°C) at low temperatures. The Janus POSS‐based hydrogel electrolyte is expected to be a promising gel electrolyte for an all‐in‐one supercapacitor that resists freezing. [ABSTRACT FROM AUTHOR]

This article, titled "Cover Image, Volume 141, Issue 2," discusses the features and applications of a new Janus POSS material. The material is hydrophilic, highly conductive, anti-freezing, and polymerizable. The article demonstrates the use of POSS as a crosslinker in a hydrogel and the structure of a flexible supercapacitor based on a hydrogel electrolyte. The cover image, created by Mr. Sen Liu, depicts the anti-freeze and electrical conductivity properties of the supercapacitor. The article is authored by Kaiqi Fan, Sen Liu, Wenbo Feng, Wentong Yang, Jiwei Peng, Ruixue Liu, Shaoming Fang, and Xiaojing Zhang. [Extracted from the article]

• Chlorella incorporated into hydrogels for continuous oxygen and bioelectric delivery. • Hydrogels offer mechanical support and create optimal microenvironment for Chlorella. • Hydrogels improve diabetic wound healing by enhancing proliferation and angiogenesis. Electrical stimulation and oxygen are vital for promoting cell proliferation, migration, and differentiation to repair damaged tissues in chronic wound healing in patients with diabetes. The effective oxygen production by Chlorella has garnered attention in the medical field, but the potential of extracellular electron production in skin repair has not been explored. Inspired by this, we developed CHPS hydrogels, a composite of polyacrylamide and sodium alginate, with Chlorella loaded in a semi-interpenetrating network. This network is formed by crosslinking acrylamide initiated by free radicals, with alginate chains dispersed within the network. When applied to wounds, CHPS hydrogels effectively protect damaged tissue, provide mechanical support to Chlorella against external forces, and create an optimal artificial microenvironment to promote the proliferation of Chlorella. Our study demonstrated that CHPS hydrogels exhibit remarkable fracture elongation and adhesion properties and continuously produce oxygen and bioelectrical currents through photosynthesis. Furthermore, the sustained release of dissolved oxygen and bioelectricity by CHPS hydrogels significantly enhances cell proliferation, migration, and angiogenesis, leading to improved wound healing in diabetic mice. These findings provide compelling evidence for further exploration of CHPS hydrogels as a cost-effective, simple, and accessible strategy for enhancing the clinical treatment of chronic wounds in diabetic patients. [ABSTRACT FROM AUTHOR]