Chlorpyrifos (CPF) and 2,4-dichlorophenoxyacetic acid (2,4-D) are insecticides and herbicides which has been widely used on farms. However, CPF and 2,4-D residues on corps can bring high risks to human health. Accurate detection of pesticide residues is important for controlling health risks caused by CPF and 2,4-D. Therefore, we developed a fast, sensitive, economical, and lossless surface-enhanced Raman spectroscopy (SERS)-based method for pesticide detection. It can rapidly and simultaneously determine the CPF and 2,4-D mixed pesticide residues on an apple surface at a minimum of 0.001 mg L−1 concentration, which is far below the pesticide residue standard in China and the EU. The limits of detection reach down to 1.28 × 10−9 mol L−1 for CPF and 2.47 × 10−10 mol L−1 for 2,4-D. The limits of quantification are 4.27 × 10−9 mol L−1 and 8.23 × 10−10 mol L−1 for CPF and 2,4-D. This method has a great potential for the accurate detection of pesticide residues, and may be applied to other fields of agricultural products and food industry.

Cordycepin, extracted from the medicinal mushroom Cordyceps militaris, was shown to induce cancer cell apoptosis. Yet its anticancer function was limitedly evaluated, and the mechanism was not entirely elucidated. In this study, we demonstrated the effectiveness of cordycepin in inducing apoptosis in HeLa cells and investigated its apoptosis-inducing mechanism through label-free surface-enhanced Raman spectroscopy (SERS). SERS spectral changes revealed detailed molecular changes in both early and late stages of apoptosis. Importantly, SERS characteristic peaks at 805 and 1438 cm⁻¹, which were assigned to RNA, continued to decrease significantly from early to late apoptosis stages. It indicated that cordycepin induced HeLa cell apoptosis mainly through interfering with RNA production, potentially by restraining the translation of RNA encoding ribosomal proteins. Meanwhile, apoptotic cells and their apoptosis stage could be easily differentiated by SERS-based principal component analysis (PCA). Furthermore, the morphological changes of early and late-stage apoptotic cells were illustrated by differential interference contrast and fluorescence microscopic imaging. Therefore, the natural ingredient, cordycepin, could serve as a promising anticancer candidate. Our biological model of cell apoptosis in vitro, the non-invasive and rapid SERS technique, combined with PCA analysis, could be a powerful tool in the investigation of cell apoptosis mechanisms and anticancer drug screening.