A rational strategy is introduced to develop label-free colorimetric assays based on aptamers and cyanine dyes that can detect small molecules for on-site sensing applications.
This dye-displacement approach is found to be generally applicable to DNA aptamers with diverse sequences, structures, and affinity, enabling the detection of a variety of analytes in a sensitive, selective, and rapid manner. Aptamers are promising biorecognition elements for sensors. However, aptamer-based assays often lack the requisite levels of sensitivity and/or selectivity because they typically employ structure-switching aptamers with attenuated affinity and/or utilize reporters that require aptamer labeling or which are susceptible to false positives. Dye-displacement assays offer a label-free, sensitive means for overcoming these issues, wherein target binding liberates a dye that is complexed with the aptamer, producing an optical readout. However, broad utilization of these assays has been limited. Here, we demonstrate a rational approach to develop colorimetric cyanine dye-displacement assays that can be broadly applied to DNA aptamers regardless of their structure, sequence, affinity, or the physicochemical properties of their targets. Our approach should accelerate the development of mix-and-measure assays that could be applied for diverse analytical applications. (Publisher Abstract)