DNA-templated electrodeposition of silver nanoparticles for direct and label-free aptasensing of ochratoxin A.

We present in this work, an aptasensing strategy based on the DNA-templated electrodeposition of silver nanoparticles (AgNPs). The homogeneous electro-deposition of AgNPs on screen printed carbon electrode (SPCE) surface was achieved based on a unique aptamer scaffold. This was constructed by immobilizing a DNA aptamer on SPCE by electrochemical oxidation of its amine groups. The electrodeposition of AgNPs was investigated before and after the addition of the aptamer's specific target; the mycotoxin, ochratoxin A (OTA). Electrochemical characterization by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed the effect of the scaffold layer on the electrodeposition of AgNPs. The conformational change induced by aptamer after binding its targeted molecule affects AgNPs electrodeposition and the electron transfer thus allowing OTA detection by cyclic voltammetry. The voltammograms showed a good proportionality between the analyte concentration and the current response. The constructed platform allowed the quantitative aptasensing of OTA within the range of (1.56-400 ng/mL) and the detection limit of 0.6 ng/mL. In term of aptasensor applicability, the proposed strategy showed excellent performance in rice samples.