A Selective, Class-Specific Aptamer for Fentanyl Analog Screening.

Fentanyl and its analogs pose considerable dangers to public health and safety, and the development of simple tests that can detect these harmful substances accurately and rapidly could control their currently unchecked spread and thereby safeguard lives. Here, we use systematic evolution of ligands by exponential enrichment (SELEX) to isolate an aptamer that displays a rare blend of high affinity and broad cross-reactivity to 139 fentanyl analogs, alongside excellent specificity against nontarget interferents, including cutting agents, adulterants, and other drugs of abuse. We demonstrate the utility of this aptamer by developing a single-step colorimetric dye-displacement assay that can detect diverse fentanyl analogs within seconds with a simple mix-and-read format. The analog coverage of our assay rivals that of commercial immunoassay-based fentanyl tests while offering better specificity against substances that commonly trigger false positives in those tests, such as diphenhydramine, lidocaine, and methamphetamine. Our findings indicate that aptamers may be fundamentally better suited for achieving broad but specific detection of structurally related classes of molecules relative to other commonly used receptors, such as antibodies, due to their excellent and controllable binding properties, among other benefits, including low cost and high stability.