Nitrogen-doped carbon dot and DNA tetrahedron nanostructure based electrochemiluminescence aptasensor for AFB1 detection

An electrochemiluminescence (ECL) aptasensor with aptamer as recognition element, N-doped carbon dots (N-CDs) as luminophore, and DNA tetrahedral nanostructure (DTN) as carrier to loading abundant N-CDs for signal amplification was developed for ultra-sensitive aflatoxin B1 (AFB1) detection. The complementary DNA (cDNA) was firstly immobilized on the Au electrode (AuE) surface to hybridize with the AFB1 aptamer. In the presence of AFB1, it would competitively with cDNA for binding the aptamer, causing the exposure of cDNA. DTN modified with AFB1 aptamer on top and N-CDs on the four vertices would combine with cDNA onto the AuE surface to generate ECL signals due to electron transfer between co-reactants (K2S2O8) and N-CDs, which was positively related to the concentration of AFB1. Due to the high specificity of aptamer, the outstanding ECL performance of N-CDs and the enhanced signal output of DTN/N-CDs probes, the as-constructed ECL aptasensor realized excellent sensitivity with a low detection limit of 77 pg/mL and a wide linear concentration of 1.0×10-1-1.0×104 ng/mL for AFB1, as well as fascinating accuracy with acceptable recoveries of 89.54-111.0% in the spiked Coix seed matrices. Successful application for AFB1 detection in actual samples confirmed the extensive practicability of the ECL aptasensor, providing a universal platform for more trace contaminants by altering the corresponding aptamers.