Development of an ultrasensitive magnetic biosensing platform using SERS and aptamer for the ratio detection of chlorpyrifos in tea.

The rapid and accurate detection of chlorpyrifos (CPF), a widely used pesticide in agricultural products, is crucial for food safety assurance. While traditional methods like HPLC and GC-MS are accurate, they remain costly, slow, and lack portability. Herein, an ultrasensitive magnetic biosensing platform was developed for the ratiometric detection of CPF in tea by integrating surface-enhanced Raman spectroscopy (SERS) with an aptamer-based recognition strategy. The platform employed a competitive displacement mechanism, where specific binding between aptamer and CPF triggered the release of signal probes upon magnetic separation. This process altered the Raman intensity ratio of two reporter molecules (4-MPY and 4-MBN). The ratiometric sensing approach, combined with magnetic separation, improved operational convenience and reduced matrix interference from complex samples. Furthermore, the platform exhibited a wide linear detection range (10-9 M to 10-4 M) with a limit of detection (LOD) of 1.4 × 10-6 mg/kg. It demonstrated high sensitivity, stability, reproducibility and specificity across six tea varieties, offering an effective solution for detecting pesticide residues in complex food matrices.