A versatile nanomachine for the sensitive detection of platelet-derived growth factor-BB utilizing a G-quadruplex-selective iridium(III) complex

The novel iridium(III) complex 1 was found to be highly selective for G-quadruplex DNA, and was employed for the development of a versatile nanomachine. In the nanomachine, the single-stranded DNA (ssDNA) oligonucleotide ON1 hybridizes with the hairpin DNA oligonucleotide ON2, leading to the formation of a 5′-recessed double-stranded DNA (dsDNA) structure and the simultaneous release of a G-rich DNA sequence, which folds into a G-quadruplex motif that is recognized by complex 1. Upon the addition of Exo III, the dsDNA substrate is digested leading to the liberation of ON1 ssDNA, which enters a new cycle of the nanomachine. This nanomachine was successfully used to detect PDGF-BB by combination with a simple pre-procedure module, and exhibited a linear response between luminescence intensity and PDGF-BB concentration in the range of 10 to 300 pM (R2 = 0.992), with a limit of detection for PDGF-BB of 10 pM. This assay was highly selective for PDGF-BB over other proteins, and exhibited potential use in biological sample analysis. Moreover, the versatility of the nanomachine was demonstrated by adapting the nanomachine for the detection of thrombin by simply changing the pre-procedure module.