Sensitive and reusable electrochemiluminescent aptasensor achieved with diblock oligonucleotides immobilized solely through preferential adenine-Au interaction.

Strong Au-S chemistry to self-assemble thiolated oligonucleotides at gold electrode is an efficient strategy to construct electrochemiluminescent (ECL) aptasensor. However, it remains challenging to precisely control the orientation and conformation of surface-tethered oligonucleotides and to reuse ECL aptasensor because of the narrow electrochemical window of thiolated DNA film on Au surface (below similar to 0.80 V versus Ag/AgCl). Here, we demonstrate adenine/thymine diblock oligonucleotides (d(Am-Tn)) to substitute DNA-SH in DNA immobilization for constructing ECL aptasensor. As a proof-of-principle, thrombin was used to present the properties of the proposed sensor. The as-formed ECL aptasensor had a wide electrochemical window and good stability (decreased 5.38% after 200 cyclic potential cycles, 0-1.2 V versus Ag/AgCl). Moreover, the aptasensor exhibited an extremely low detection limit (0.017 pM) and offered good selectivity toward thrombin. This detection limit was at least one order of magnitude lower than those of previous methods for thrombin. Additionally, the ECL aptasensor was reusable (n = 3) and showed good reproducibility (relative standard derivation, 4.7% (n = 6)). We believe that the strategy demonstrated here provides a good platform for DNA immobilization in constructing ECL even electrochemical aptasensor for the detection of targets in clinical analysis conveniently.