Chemiluminescence Sensor Based on Composite Functional Nucleic Acid for Detection of Ochratoxin A in Wine

A chemiluminescence (CL) sensor, using ochratoxin A (OTA) aptamer as the activation switch of the split DNAzyme, was established to achieve high-sensitivity detection of OTA in wine. A guanine-rich oligonucleotide can fold into a parallel G-quadruplex in K+ solution. Hemin as a ligand can bind to parallel G-quadruplexes precisely. Hemin-G-quadruplex complexes display peroxidase-like activity, named as DNAzyme. The activity of the DNAzyme can be measured by CL via the H2O2 mediated-oxidation with luminol. Guanine-rich oligonucleotide split into two fragments; when they were near each other, they could reform DNAzyme. OTA aptamer as a switch was inserted into the nucleic acid sequence of DNAzyme. In the absence of OTA, the unfolded OTA aptamer inhibited the split DNAzyme effective self-assemble to form a structure with enzymatic activity. In the presence of OTA, OTA induced the aptamer to form an antiparallel G-quadruplex and drew the tail of the aptamer closer so that the two fragments of split DNAzyme refolded and compound with hemin. The folding degree of the aptamer would directly affect the activity of DNAzyme and high-sensitivity detection of OTA could be obtained by monitoring the enhanced ratio of CL intensity. The linear range of this method was 0.10–2.00 nmol/L, and the limit of detection was 0.10 nmol/L.