A redox-mediated chromogenic reaction and application in immunoassay

•A novel kind of chromogenic reaction was demonstrated which could be mediated by redox substance.•The mechanism based on the reaction between HAuCl4 and ABTS.•It has been successfully adapted to the sensitive detection of both catalase and disease biomarkers

A novel redox-mediated chromogenic reaction was demonstrated based on the reaction between HAuCl4 and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), which generate various color responses from red to green in the resulting solutions. Various redox substance could be used to mediate the reaction and trigger a distinct color response. We established a sensitive hydrogen peroxide colorimetric sensor based on the redox-mediated chromogenic reaction and depicted the application both in detection of enzyme and in an immunoassay. Combining the traditional chromogenic reagent with gold nanoparticles, our assay has the advantage in short response time (within three minutes), high sensitivity (10−12 g mL−1 for HBsAg) and stability.

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