Label-free colorimetric detection of coralyne utilizing peroxidase-like split G-quadruplex DNAzyme

Abstract

A simple design of a label-free colorimetric sensor for coralyne was demonstrated, which is based on the coralyne-modulated peroxidase-like split G-quadruplex (split G4) DNAzyme via A₂–coralyne–A₂ coordination. In the present work, two specific oligonucleotide strands were used. Upon addition of coralyne, it could specifically bind to A18 sequences with an apparent binding constant of 1.05 × 10⁵ M⁻¹, which induced the formation of an anti-parallel homo-adenine duplex, accompanied by the proximity of two G-rich sequences responsible for the formation of split G4. In the presence of hemin, this split G4 was able to catalyze the H₂O₂-mediated oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid) diammonium salt (ABTS–H₂O₂ system), resulting in a maximal absorbance at approximately 420 nm. A linear response from 0.06 to 10 μM was obtained for coralyne, with a linear correlation coefficient of 0.9987. The detection limit was estimated to be 19 nM based on a S/N of 3.