Target-induced strand release and thionine-decorated gold nanoparticle amplification labels for sensitive electrochemical aptamer-based sensing of small molecules

A sensitive and selective electrochemical aptamer sensing platform for adenosine based on target-induced strand release and gold nanoparticle (AuNP) amplification labels is developed. The association of the target adenosine with the corresponding aptamer leads to the release of the thiol c-DNA strands from the aptamer/c-DNA duplexes. The released thiol c-DNA strands are captured on a gold sensing electrode by their complementary sequences through DNA hybridizations. The AuNPs are then attached to the surface-hybridized thiol c-DNA strands via Au-S bond. These AuNPs further adsorb a large number of electroactive species, thionine, on their surfaces, which leads to significantly amplified current response for highly sensitive monitoring of adenosine down to 0.05 nM. Besides, the proposed method shows excellent selectivity toward adenosine against other analogous interference molecules due to the high specificity of the aptamer recognition capability. Moreover, by changing the corresponding specific aptamer recognition strands, the proposed method can offer a more general sensing platform for the detection of low levels of various types of biomolecules (proteins, cells, amino acids, etc.). (C) 2014 Elsevier B.V. All rights reserved.