# Dual-Mode Plasmonic Colorimetric/Photothermal Aptasensor for OTA: Based on a Mn2+-Powered DNA Walker for Mediating AuNB Growth

## TL;DR

A new biosensor detects ochratoxin A with high sensitivity and specificity using a DNA walker and gold nanoparticles, offering a green and efficient detection method.

## Contribution

A dual-mode plasmonic/photothermal aptasensor using a Mn2+-powered DNA walker for ultrasensitive OTA detection is introduced.

## Key findings

- The aptasensor achieved a detection limit of 48.6 pg mL−1 in colorimetric mode and 37.6 pg mL−1 in photothermal mode.
- The sensor demonstrated high specificity with cross-reactivity below 6.2% for other analytes.
- The method was successfully applied to agricultural byproduct samples, confirming its practicality.

## Abstract

The sensitive and efficient detection of ochratoxin A (OTA) is critical for protecting agricultural ecosystems and public health. A dual-mode plasmonic colorimetric/photothermal aptasensor, based on a Mn2+-powered DNA walker for mediating gold nanobipyramid (AuNB) growth, is proposed for OTA detection in this study. In sensing the target OTA, the walking DNA (W-DNA) on the magnetic walker probe was independent and then the environment-friendly Mn2+ powered the generation of DNAzyme, where abundant thiol-modified DNA (DNA-SH) was produced by autonomous walking. The positively related DNA-SH level could mediate AuNB growth and reflect dual-mode plasmonic signals. Ultrasensitivity is demonstrated with a limit of detection (LOD) value of 48.6 pg mL−1 for colorimetric mode and 37.6 pg mL−1 for photothermal mode. The aptasensor exhibited high specificity (with cross-reactivity values below 6.2% for other analytes) and high reliability for OTA detection. The requisite practicability and accessibility are verified via its application in agricultural byproduct samples. The findings of this study offer an alternative and efficient biosensing pathway for improving detection performance, enabling green, enzyme-free, homogeneous, and dual-mode strategies for monitoring other pollutants.