Distance-Based\nFluorescent Immunosensor for Point-of-Care\nTest of Illegal Additives through the Gas-Producing Nanozyme

The colorimetric point-of-care test (POCT) offers a rapid\nand efficient\nmethod for detecting specific targets in real samples. However, traditional\ncolorimetric methods often rely on complex signal amplification techniques\nor electronic devices to enhance detection sensitivity, which can\ninadvertently increase both cost and time, thus contradicting the\nfundamental goals of visual detection methods. Here, we presented\na distance-based fluorescent immunosensor that utilized a gas-producing\nnanozyme for continuous gas production reaction as a signal. Specifically,\nthe SOM-ZIF-8@Pt nanozyme catalyzed the production of O<sub>2</sub> from H<sub>2</sub>O<sub>2</sub> to cause an obvious increase in\nthe pressure within a sealed chamber, thus driving the production\nof H<sub>2</sub>S to quench the fluorescence of CsPbBr<sub>3</sub> on the walls of the capillaries. Based on the competitive immunoassay,\nthe fluorescence quenching lengths were relative with the concentration\nof aminopyrine in the range from 0.2 to 20 ng/L; thus, the fluorescent\nPOCT-based homemade device was realized through the amplification\nof distance-based signals facilitated by the continuous gas production\nreaction. This strategy provides an effective way to realize POCT\nassays in resource-limited areas by transforming pressure variations\ninto directly observable signals. Furthermore, distinguished by its\nhigh sensitivity, ease of operation, and portability, it also represents\na significant advancement in biomedical diagnostics, particularly\nwithin home healthcare and clinical POCT.