Digital SERS-lateral flow immunoassay platform for ultrasensitive and dosage-sensitive analysis of sibutramine

Rapid detection techniques play a critical role in the field of food hazard factor analysis, as food safety constitutes a fundamental cornerstone of public health. However, the application of Surface-Enhanced Raman Scattering (SERS)-lateral flow immunoassay (LFIA) as a rapid detection method in this area still faces significant challenges. Consequently, traditional quantification methods that rely on average Raman signal intensity often prove inadequate for accurate measurement under such conditions. In response to these limitations, we developed a digital SERS-LFIA approach, which employs digital analytical techniques to process Raman spectral data for the ultrasensitive and quantitative analysis of sibutramine (SIB), a central appetite suppressant formerly used in obesity treatment that is now frequently illicitly added to foods such as weight-loss teas. Specifically, the method utilized core-shell Ag-coated Au nanoparticles functionalized with Raman reporter molecules as SERS tags. SERS-LFIA strips were prepared via antigen-antibody recognition for SIB detection. Rapid Raman mapping of the T-line region generated spatially resolved signal matrices, which were converted to binary values 0/1 by applying an intensity threshold at the reporter's characteristic peak. Quantification was accomplished by correlating the positive signal frequency with SIB concentration, effectively mitigating the interference caused by signal heterogeneity and background signals on quantification. Compared with conventional Raman average intensity analysis, the digital SERS-LFIA achieved limits of detection of 0.28 ng/mL, demonstrating excellent quantitative detection capability. In summary, by incorporating digital SERS technology, this study extends the application of LFIA to enable ultrasensitive and efficient quantitative detection analytes in complex food samples.