A simple adenosine fluorescent aptasensor based on the quenching ability of guanine

Based on guanine (G)-quenching, a simple and sensitive fluorescent aptasensor for the detection of adenosine was constructed. G located on the end of a DNA strand was selected as a fluorescence quencher of a FAM fluorophore. The FAM-labeled adenosine aptamer (FAM-DNA) was partly complementary to the DNA sequence containing five G on the end. In the absence of adenosine, the hybridization between FAM-DNA and complementary strand cause G to approach FAM, hence, the fluorescence of FAM was effectively quenched by the photoinduced electron transfer (PET) between FAM and G. In the presence of adenosine, FAM-DNA reacts with adenosine and starts structural switching, resulting in the release of the complementary strand and the recovery of the fluorescence of FAM. The linear detection range of adenosine with present proposed sensor is 20–200 μM, and the detection limit down to 6.7 μM (S/N = 3). Most importantly, no organic dye molecules-labeled DNA or extra nanomaterials were used as quenchers in this proposed adenosine detection strategy. The method is simple, sensitive and inexpensive and has potential for application in clinical diagnostic assays.