Ratiometric fluorescent detection of exosomal piRNA-823 based on Au NCs/UiO-66-NH and target-triggered rolling circle amplification.

piR-823 is a newly discovered colorectal cancer marker with high diagnostic efficacy. However, the current quantification methods have complicated operations and high cost, which restrict its clinical application. Herein, a metal-organic framework (MOF) with a UiO-66 prototype structure which supports gold nanoclusters (Au NCs), Au NCs/UiO-66-NH, were prepared as a model nanobiosensing platform for ratiometric detection of exosomal piR-823. The rolling circle amplification process provides high sensitivity and the ratiometric detection process ensures good accuracy of the sensor. Such biosensor showed a wide linear range of 0.04-4 pM, and a low detection limit of 10.2 fM towards piR-823. In addition, piR-823 can be used as an effective supplement to carcinoembryonic antigen (CEA) in clinical diagnosis of colorectal cancer. This study not only provides a potentially valuable ratio fluorescence platform involving enzyme catalytic reaction, but also offers a design blueprint for further expansion of nanotechnology in the diverse biological analysis.