A novel enzyme-free and label-free fluorescence aptasensor for amplified detection of adenosine

A novel enzyme-free and label-free fluorescence aptasensor based on target-catalyzed hairpin self-assembly is developed for amplified detection of adenosine. This aptasensor contains four DNA strands termed as aptamer-catalysis strand, inhibit strand, hairpin structures H1 and H2 which are partially complementary. Meanwhile, a sequence that can form DNA G-quadruplex is partly hidden in the stem of H2. In the absence of adenosine, aptamer-catalysis strand is inhibited, and cannot trigger the self-assembly between H1 and H2. Upon the addition of adenosine, the binding event of aptamer and adenosine triggers the self-assembly between H1 and H2, resulting in the formation of G-quadruplex at the end of H1-H2 complex. The addition of N-methyl mesoporphyrin IX, which has a pronounced structural selectivity for G-quadruplex, generates label-free fluorescence signal. In the optimum conditions, we could detect adenosine as low as 6 μM by monitoring the change in fluorescence intensity. Furthermore, this amplified aptasensor shows high selectivity toward adenosine against its analogs due to the specific recognition ability of the aptamer for the target. Thus, the proposed aptasensor could be used as a simple and selective platform for target detection.