Label-Free Luminescent Switch-On Probe for Ochratoxin A Detection Using a G-Quadruplex-Selective Iridium(III) Complex

A library of six luminescent Ir(III) complexes were synthesized and studied for their capacity to function as probes for G-quadruplex DNA. The novel Ir(III) complex 1 was discovered to be selective for G-quadruplex structures and was subsequently used for the construction of a label-free G-quadruplex-based ochratoxin A (OTA) sensing platform in aqueous solution. The assay exhibited linearity for OTA in the range of 0 to 60 nM (R2 = 0.9933), and the limit of detection for OTA was 5 nM. Furthermore, this assay was highly selective for OTA over its structurally related analogues.