A Co-locked hairpin probe enabling triple-cascaded signal amplification for the photoelectrochemical detection of dibutyl phthalate.

Abstract

The sensitive detection of dibutyl phthalate (DBP) is essential for environmental pollution assessment and health risk warning. Although the DNA-based cascade signal amplification strategy can significantly improve the detection sensitivity, non-specific background leakage during amplification remains an unavoidable issue that severely limits the practical performance of sensors. This study developed a co-locked hairpin enabling triple-cascaded signal amplification approach to avoid the non-specific background leakage for ultra-sensitive detection of DBP. Specifically, FeIn2S4/In2O3 heterojunction was constructed to enhance the initial photocurrent signal. Upon activation by the target DBP, the DNAzyme cleaved the co-locked hairpin to release the initiator and fuel strands. These strands further initiated entropy-driven reaction (EDR) to produce the output DNA, which ultimately triggered the hybridization chain reaction (HCR) to generate abundant double-stranded DNA (dsDNA) structures. Subsequently, acridine orange (AO) was intercalated into these HCR-generated dsDNA structures as a photosensitizer to amplify the photocurrent signal. Notably, the co-locked hairpin enabling triple-cascaded signal amplification strategy effectively suppresses non-target signal leakage in the cascade DNA circuit, significantly improving the sensitivity and accuracy of the sensor. The PEC sensor exhibited a linear detection range for DBP from 1 fmol L-1 to 1 nmol L-1, achieving an ultralow detection limit of 0.27 fmol L-1. This study offers a reliable method for precise detection of DBP in the environment and shows promising applications in the field of environmental pollutant monitoring.