Ultrasensitive and universal fluorescent aptasensor for the detection of biomolecules (ATP, adenosine and thrombin) based on DNA/Ag nanoclusters fluorescence light-up system

We report here an ultrasensitive strategy based on the recognition-induced conformational alteration of aptamer and fluorescence turn-on abilities of guanine-rich (G-rich) DNA sequence in proximity to silver nanoclusters for adenosine triphosphate (ATP), adenosine (A) and thrombin (TB) detection. Herein, we designed two tailored DNA sequences noted as complementary DNA (abbreviated as c-DNA) and signal probe DNA (abbreviated as s-DNA), respectively. c-DNA is designed as a special structure consisting of a sequence complementary to aptamer at the 3′-end and a guanine-rich DNA sequence at the 5′-end; s-DNA contains a cytosine-rich sequence responsible for Ag NCs templated synthesis at the 3′-end and a link sequence (part of aptamer) complementary to partial of the c-DNA at the 5′-end. In the presence of target, the aptamer associated with the target, resulting in the formation of duplex DNA (dsDNA), the DNA–Ag NCs thereafter could close to the guanine-rich sequence, leading to enhanced fluorescence signal readout. The widespread application of the sensing system is achieved success in the detection of three biomolecules . ATP, adenosine and thrombin in the range of 0.5-8.0   μM, 0.5-7.0   μM and 50-900   nM could be linearly detected with the detection limits of 91.6   nM, 103.4   nM and 8.4   nM, respectively. This label-free and turn-on fluorescent sensing system employing the mechanism proposed here turns out to be sensitive, selective, and convenient for the detection of biomolecules without washing and separation steps.