A novel immunochromatographic assay (ICA) based on surface-enhanced Raman scattering for the sensitive and quantitative determination of clenbuterol

In this study, we present a novel immunochromatographic assay (ICA) based on surface-enhanced Raman scattering (SERS) for the sensitive and quantitative determination of clenbuterol in urine samples. The principle of this new ICA is similar to that based on colloidal gold particles, but using AuMBA@Ag–Ab [e.g. the polyclonal antibody of clenbuterol labelled Au@Ag core–shell nanoparticles (NPs) sandwiched with a Raman reporter (4-mercaptobenzoic acid, MBA)] as a probe. The clenbuterol in solution and the clenbuterol–ovalbumin conjugate previously coated on the test line of the ICA strip competed for limited antibody binding sites on the probe. The specific Raman scattering intensity of MBA on the test line was measured for the quantitative detection of clenbuterol. This proposed assay was completed within 15 min. The IC50 and limit of detection (LOD) values of the assay for clenbuterol were found to be 0.02 ng mL−1 and 0.24 pg mL−1, respectively. The relative standard deviations (RSD) of the signal obtained from 10 points along the middle part of the test line were within 4.3–8.7%. There was no cross-reactivity (CR) of the assay with ractopamine or phenylethanolamine A, and only 19% CR with salbutamol. The recoveries of clenbuterol from spiked swine urine samples were in the range of 93.8–112.4% with RSD values in range of 5.2–11.5% (n = 9). The proposed SERS-based ICA was demonstrated to be a rapid, simple and ultrasensitive analytical method for detecting clenbuterol in urine samples and could also be applied for the determination of other target analytes in different matrices.