Cell-Inspired\nMicroreactor with Compartmentalized\nActive Sites for Development of Cascade Catalysis System in Biosensing

Enzymatic cascade reactions with high activity and specificity\nin living cells always benefit from multicompartmentalized organelles\nthat provide separately confined spaces for enzymes, avoiding their\nmutual interference to ensure\nthe high-efficiency operation of necessary vital movements. Inspired\nby this, we designed a 3D spherical microreactor (Au@H-APF@Pt) with\nbiomimetic cascade catalysis for glucose detection. First, ultrasmall\ngold nanoparticles were immobilized in situ on the internal cavities\nof hollow 3-aminophenol formaldehyde resin (H-APF) nanospheres, along\nwith glucose oxidase activity. Then, platinum nanoparticles (PtNPs)\nwith peroxide-like activity were reduced surrounding the outer layer\nof the H-APF nanospheres. Similar to the cell structure, different\nmetal sites in this bifunctional microreactor operated independently,\nbringing higher catalytic activity and selectivity and thus being\nsynergistically capable of a cascade reaction to catalyze the substrate\nfor glucose detection. This cell-mimicking microreactor (Au@H-APF@Pt)\nwas successfully applied in glucose colorimetric detection, showing\na 1.9-fold activity enhancement compared to direct mixing (Au/Pt).\nThe observed low catalytic activity was attributed to the extended\ntime for transferring hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) from Au NPs to the solution and then to PtNPs. Integrating a smartphone\nAPP, a real-time, visual, and Au@H-APF@Pt-based hydrogel sensor for\nglucose detection was also proposed. Satisfactory results highlight\nthat this cell-mimicking microreactor offers a very successful strategy\nto improve the efficiency of cascade catalysis systems in biosensing.