Abstract
We report a label-free aptasensor to make direct detection of prostate specific antigen (PSA, a biomarker of prostate cancer) using a quinone-containing conducting copolymer acting as redox transducer and grafting matrix for immobilization of the short aptamer strands. It is shown that capture of PSA generates a current decrease (signal-off) measured by Square Wave Voltammetry. This current decrease is specific for PSA above a limit of quantification in the ngmL−1 range. The change in current is used to determine the PSA–aptamer dissociation constant KD, of ca. 2.6nM. To consolidate the proof of concept, a heterogeneous competitive exchange with a complementary DNA strand which breaks PSA–aptamer interactions is studied. This double-check followed by a current increase provides full assurance of a perfectly specific recognition.
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