A multicolor colorimetric aptasensor for visual detection of quinclorac based on G-quadruplex DNAzyme-mediated gold...

The development of gold nanobipyramid (AuNBP)-based multicolor colorimetric aptasensors offers significant advantages for enabling sensitive, accurate, and visual on-site detection. However, existing AuNBP growth-based strategies suffer from the inherent limitations of enzymes and the instability of AuNBPs that restrict their application in aptasensor construction. In this study, a multicolor colorimetric aptasensor based on a novel G-quadruplex (G4) DNAzyme-mediated AuNBP growth strategy was developed for the detection of quinclorac (QNC), a prevalent acid herbicide. First, complexes of magnetic bead (MB)-QNC aptamer (Qapt)-G4 DNA were formed through an MB-assisted competitive aptamer-binding system. In this system, the amount of MB-aptamer-G4 DNA complexes formed was directly proportional to the QNC concentration. These complexes subsequently facilitated the G4 DNAzyme-catalyzed oxidation of hydroquinone (HQ). The remaining HQ was then utilized to grow AuNBPs, leading to distinct multicolor variations. Under optimal conditions, the aptasensor exhibited nine discernible color changes corresponding to different QNC concentrations with a visual limit of detection (LOD) of 0.5 μM and an instrumental LOD of 113 nM. Moreover, the aptasensor demonstrated excellent specificity and color stability. It was successfully used to determine QNC in river water, soil, and rice samples with recovery rates of 95.20 %-100.69 % and relative standard deviations (n = 5) < 3 %. These results indicate that it is a reliable and promising method for the rapid screening of QNC residues in environmental and food samples. Furthermore, this work provides a valuable reference strategy for transforming G4 DNAzyme-based colorimetric aptasensors into multicolor analytical platforms.