“Off-on” signal-switchable electrochemiluminescence aptasensor based on Cu2O-ABEI-AgNPs mediated signal amplification for the detection of profenofos

Abstract

An “off-on” signal-switchable electrochemiluminescence (ECL) aptasensor was designed for the detection of profenofos based on Cu2O-ABEI-AgNPs as ECL enhancers. Cubic Cu2O was prepared as a core, and AgNO3 was reduced to silver nanoparticles (AgNPs) by N-(4-Aminobutyl)-N-ethylisoluminol (ABEI) as a shell on the Cu2O surface. The Cu2O with a large surface area could enhance the fixation of AgNPs. Cu2O and AgNPs were utilized as catalysts to enhance the double amplification ECL signals. Additionally, a molecular probe consisting of gold nanoparticles (AuNPs), a T-type aptamer (consisting of thymines “T”, referred to as TApt), and aptamer (Apt) was prepared (referred to as AuNPs-Apt-TApt). The presence of mercury ion (Hg2+) could potentially quench the ECL signal and bind the thymine-Hg2+-thymine (T-Hg2+-T) structure. The structure formed a probe with Apt and AuNPs. The complementary short chain of aptamer (CApt) was designed and immobilized on AgNPs. In the absence of profenofos, the Apt and CApt were bound through complementary base pairing. The probe was immobilized on the electrode, resulting in quenching of the signal (switched into “off”). However, upon the presence of profenofos, the probe was detached from the electrode, and the signal was restored (switched into “on”). Finally, the aptasensor had a broad detection range (1 ×10-3 ng/mL∼1 ×102 ng/mL) with a lower limit of detection (LOD, 3 ×10-4 ng/mL) and an excellent recovery rate (94.34%∼113.80%) for the detection of profenofos in vegetables. The aptasensor had good stability, repeatability and specificity.