Novel Clean-Background Coffee Ring SERS Platform for Trace Toxin Analysis

Biotoxins, known for their ubiquity and potent toxicity, pose significant threats to ecosystems and human health, highlighting the urgency the development of robust detection methods. Despite the significant potential of surface-enhanced Raman spectroscopy (SERS) in analytical science, challenges emerge when dealing with low Raman active molecules, such as biotoxins. Our study addresses this by introducing an innovative, ultrasensitive, clean-background coffee ring SERS (CC-SERS) platform, specifically designed for the detection of neo-saxitoxin (neo-STX), saxitoxin (STX), microcystin-LR (MC-LR), and microcystin-RR (MC-RR) using the AgNPs@Ag₂O@AgCl coffee rings. By fine-tuning surface ligands and laser wavelength, a clean SERS background was obtained for the accurate detection of biotoxins. The CC-SERS platform exhibited a strong linear response for STX, neo-STX and microcystins (MC-LR and MC-RR) with limit of detection (LOD, 3δ/k) of 3.3, 1.3, 2.2 and 2.2 nM, respectively. By employing principal component analysis (PCA), we effectively differentiated between highly similar biotoxins, ensuring precise identification within complex samples. The accuracy and sensitivity of this detection platform were validated through high-performance liquid chromatography (HPLC) and high-performance liquid chromatography–mass spectrometry (HPLC-MS) analysis of real samples, indicating its promising application in ensuring food safety.