Light-activated oxidative capacity of isoquinoline alkaloids for universal, homogeneous, reliable, colorimetric assays with DNA aptamers

Aptamers are good affinity receptors for bio-assays, while colorimetric method is suitable for point-of-care sensing via direct visualization. But previously aptamers often need complex re-engineering for colorimetric measurement at the cost of affinity and performance. Here isoquinoline alkaloids are found to own unique light-activated oxidative capacity, which can be specifically triggered by unmodified aptamers. This feature is universal for two alkaloids to efficiently oxidize four chromogenic substrates with obvious color changes. Based on a dye-displacement process, we have developed a novel light-activated aptamer system for the colorimetric assay of estradiol. It shows a good sensitivity with a detection limit of 326 nM, and this homogeneous assay is reliable to avoid artifacts in previous heterogeneous scheme. Besides, it is proven to be a universal design to assay other two targets. Significantly, they do not employ any aptamers re-engineering but only simply use their parental aptamers. Therefore, this light-activated oxidative capacity of isoquinoline alkaloid can serve as an ideal tool for colorimetric assay of various targets based on aptamer's specific recognition.