A signal-on electrochemical probe-label-free aptasensor using gold–platinum alloy and stearic acid as enhancers

In the present study, a new electrochemical probe-label-free aptasensor for thrombin (TB) based on the amplification of gold–platinum alloy nanoparticles (Au–PtNPs) and stearic acid was reported. Nafion@multiwalled carbon nanotubes (MWCNTs) coated electrode was firstly modified with electrochemical probe of methylene blue (MB). Then, Au–PtNPs were electrodeposited onto the electrode surface for the immobilization of aptamer and further hybridization of stearic acid labeled thrombin aptamer (TBA). In the presence of TB, the TBA bound with TB and released from the self-assembled duplex on the electrode into solution, decreasing the steric hindrance of the aptasensor and facilitating catalytic efficiency of Au–PtNPs in the presence of MB toward H2O2 with an enhanced electrochemical signal. With the enhanced effect of Au–PtNPs/MB modified electrode and stearic acid, a detection limit as low as 3 pM for TB was achieved. The aptasensor also exhibited good selectivity and reproducibility.