Colorimetric detection of exosomal microRNA through switching the visible-light-induced oxidase mimic activity of acridone derivate.

Exosomal microRNAs (miRNAs) are vital biomarkers for early diagnosis and prognosis monitoring of cancer. Yet, convenient and controllable detection of exosomal miRNA still remains challenges because of lacking of adequately simple and robust assay platforms. In this paper, it is first time to study the visible-light-induced oxidase mimic activity of 10-methyl-2-amino-acridone (MAA) being able to be switched by Cu2+ and DNA. Based on this phenomenon, a series of visual molecular logic gates are constructed, and a colorimetric strategy has been developed to achieve exosomal microRNA-21 (miR-21) detection with a signal amplification approach. The visible-light-induced oxidase mimic activity of MAA can be inhibited by Cu2+. In presence of target, a large amount of capture probes partly complementary with miR-21 are hydrolyzed with the assist of duplex-strand specific nuclease (DSN), releasing guanine-rich oligodeoxynucleotides that can chelate Cu2+, resulting in catalytic activity of MAA being recovered under irradiation. This strategy allows the detection of miR-21 with a light modulating temporal controllable manner, and the linear range is from 50 fM to 3000 fM with the limit of detection (LOD) being 44.76 fM. More importantly, the proposed method can achieve quantitative measurement of exosomal miR-21 that is derived from three-dimensional multicellular tumor spheroids with different size, which is able to monitor the growth of tumor spheroids. This work is potential to provide a feasible tool for application in exosomal miRNAs-based cancer diagnosis. Ultimately, MAA is expected to be a signal probe in biomedical field by virtue of its fascinating visible-light-induced oxidase mimic activity.