Highly sensitive electrochemiluminescent biosensor for adenosine based on structure-switching of aptamer

A highly sensitive and selective electrochemiluminescent (ECL) biosensor for the determination of adenosine was developed. Single DNA (capture DNA) was immobilized on the gold electrode through Au–thiol interaction at first. Another DNA modified with tris(2,2′-bipyridyl) ruthenium(II)-doped silica nanoparticles (Ru-SNPs) that contained adenosine aptamer was then modified on the electrode surface through hybridizing with the capture DNA. In the presence of adenosine, adenosine–aptamer complex is produced rather than aptamer–DNA duplex, resulting with the dissociation of Ru-SNPs-labeled aptamer from the electrode surface and the decrease in the ECL intensity. The decrease of ECL intensity has a direct relationship with the logarithm of adenosine concentration in the range of 1.0 × 10−10 to 5.0 × 10−6 mol L−1. The detection limit of the proposed method is 3.0 × 10−11 mol L−1. The existence of guanosine, cytidine and uridine has little interference with adenosine detection, demonstrating that the developed biosensor owns a high selectivity to adenosine. In addition, the developed biosensor also demonstrates very good reusability, as after being reused for 30 times, its ECL signal still keeps 91% of its original state.