Arrayed complexes of a water-soluble deep cavitand and two fluorescent indicators show selective sensing of anabolic-androgenic steroids in aqueous environments. By combining the host-guest complexes with small amounts of heavy metal ions, discrimination between steroids that vary in structure by only a single π bond is possible. The sensing occurs through a triggered aggregation mechanism, which can be mediated by both the presence of metal ions and the steroids. The use of both "turn-on" and "turn-off" fluorophores is essential for good discrimination. As low as 10 μm steroid can be detected, and the discrimination is selective in steroid samples spiked into human urine.
Keywords: Aggregation; Biosensors; Host-guest systems; Molecular recognition; Receptors.
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