Double-Network structure chemically programmed DNA Cryogel: Enzyme immobilization platform with enhanced catalytic activity for portable biosensing

Enzyme-based hydrogels have conferred multiple benefits, particularly for disease diagnosis and environmental monitoring due to their pronounced biocompatibility, ability to load cargo, and optical properties. However, traditional hydrogels suffer from some significant limitations, such as enzyme leakage and catalytic activity decreased, restricting the extent to which hydrogels can be beneficially used. Herein, chemically programmed DNA-DNA interactions were designed as a promising solution for enzyme immobilization that substantially maintains biological functionality with remarkable leakage reduction. Additionally, their responsiveness and mechanical properties are dramatically enhanced after adjusting the porous structure of hydrogels via freezing. As a proof-of-concept, a DNA cryogel with a hierarchical structure was developed with adjustable distance among cascade enzymes, increasing the local concentration of intermediates and reducing their mass transfer energy barriers for direct glucose monitoring and glutathione (GSH) sensing. Moreover, after being integrated with a smartphone system, a universal sensing platform (immunosensor) was fabricated for rapid detection of environmental chemicals (i.e., bisphenol A) without expensive instruments and sophisticated procedures. This strategy provided some novel insights on hydrogel- based bioassays, implying their great potentials for conducting onsite analysis against various targets.