An aptamer-based and pyrene-labeled fluorescent biosensor for homogeneous detection of potassium ions.

A simple and homogeneous method based on aptamer and pyrene moieties for the detection of K(+) was developed. The aptamer was labeled by pyrene moiety at 3' end as the molecular recognition element. In the presence of K(+), the complementary oligonucleotide labeled by pyrene moiety at 5' end was displaced from the aptamer, which was accompanied by a dramatic decrease of the excimer fluorescence of pyrene. However, the excimer fluorescence remains in the absence of the target. With optimum conditions, relative changes of the pyrene excimer fluorescence intensity were proportional to the concentrations of K(+) in the range of 6.3 × 10(-4) to 1.0 × 10(-2) M with a detection limit of 5.0 × 10(-4) M. Importantly, in the presence of Na(+), NH(4)(+), Mg(2+) and Ca(2+) cations of biological fluids, this method was able to detect K(+) with high selectivity. In a word, the assay seems to have great potential applications, especially in biological fluids due to its simplicity, specificity and homogeneous detection.