Dynamic stability and self-healing ability are two inherently compatible properties for living organisms. By contrast, kinetic stability and intrinsic healability are two desired but mostly incompatible properties for synthetic materials. This is because the healing of these materials heavily relies on the kinetic lability of the chemical bonds or physical interactions in materials. Inspired by the hierarchically and temporally controlled wound healing in biological systems, here, we report the intrinsic healing of kinetically stable hydrogels, regulated by the consumption of chemical nutrients. The acylhydrazone-based polymer hydrogels with preinstalled urease and urea were formed at a low initial pH, followed by in situ enzymatic generation of a base to deactivate the dynamic bonds, allowing efficient fabrication of kinetically stable hydrogels. The healing of damaged hydrogels was effective when fed with proper chemical nutrients (i.e., acidic urea solutions), in which case a transient acidic pH state was temporally programmed by combining a fast acidic activator (for structural healing) with the slow, biocatalytic generation of a base (for property recovery). The ability to regulate both hydrogel fabrication and healing via a single enzymatic reaction could provide a new approach to create kinetically stable materials capable of healing damages on demand.

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The enzyme-regulated healable polymeric hydrogels are a kind of emerging soft material capable of repairing the structural defects and recovering the hydrogel properties, wherein their fabrication, self-healing, or degradation is mediated by enzymatic reactions. Despite achievements that have been made in controllable cross-linking and de-cross-linking of hydrogels by utilizing enzyme-catalyzed reactions in the past few years, this substrate-specific strategy for regulating healable polymeric hydrogels remains in its infancy, because both the intelligence and practicality of current man-made enzyme-regulated healable materials are far below the levels of living organisms. A systematic summary of current achievements and a reasonable prospect at this point can play positive roles for the future development in this field. This Outlook focuses on the emerging and rapidly developing research area of bioinspired enzyme-regulated self-healing polymeric hydrogel systems. The enzymatic fabrication and degradation of healable polymeric hydrogels, as well as the enzymatically regulated self-healing of polymeric hydrogels, are reviewed. The functions and applications of the enzyme-regulated healable polymeric hydrogels are discussed.

A strategy to rationally design and systematically optimize polymers for the efficient delivery of specific therapeutics is highly needed. The combinatorial polymer library approach could be an effective way to this end. The post-polymerization modification of reactive polymer precursors is applicable for the combinatorial synthesis of a library of functional polymers with distinct structural diversity across a consistent degree of polymerization. This allows for parallel comparison and systematic evaluation/optimization of functional polymers for efficient therapeutic delivery. This review summarizes the key elements of this combinatorial polymer synthesis approach realized by post-polymerization modification of reactive polymer precursors towards the development and identification of optimal polymers for the efficient delivery of therapeutic agents.

Ammonia detection technologies are very important in environment monitoring. However, most existing technologies are complex and expensive, which limit the useful range of real-time application. Here, we propose a highly sensitive and selective optical sensor for detection of ammonia (NH) based on liquid crystals (LCs). This optical sensor is realized through the competitive binding between ammonia and liquid crystals on chitosan-Cu that decorated on glass substrate. We achieve a broad detection range of ammonia from 50 ppm to 1250 ppm, with a low detection limit of 16.6 ppm. This sensor is low-cost, simple, fast, and highly sensitive and selective for detection of ammonia. The proposal LC sensing method can be a sensitive detection platform for other molecule monitors such as proteins, DNAs and other heavy metal ions by modifying sensing molecules.