Abstract: 【Objective】 This study was aimed to establish a rapid,sensitive,specific and easy-to-use surface-enhanced Raman spectroscopy (SERS) combined with immunochromatographic assay for detecting cephalexin.【Method】 In this study,Raman molecule 5,5’-dithiobis-2-nitrobenzoic acid (DTNB) and cephalexin antibody were conjugated with Au (core)@Ag (shell) nanoparticle to serve as SERS nanoprobe.The gold nanoparticles and Au (core)@Ag (shell) nanoparticles were identified by transmission electron microscopy(TEM) and ultraviolet spectrophotometer.Using the combination of SERS and immunochromatography,the quantitative detection technology of cephalexin was established,and applied to the detection of milk samples.【Result】 The results of TEM and ultraviolet spectrophotometer showed that silver nanoparticles were successfully coated on the surface of gold particles.Raman spectrometer was used to detect the characteristic peaks of Raman signal molecules on the immunochromatographic strip,and the peak height was selected to determine the content of cephalexin.The molecular characteristic peaks of Raman signal were 1 062,1 154,1 334 and 1 558 cm^-1,of which the characteristic peak signal at 1 334 cm^-1 was the strongest.The peak height was selected to determine the content of cephalexin.The detection linear range was 0 to 1 ng/mL,the detection limit was 0.001 ng/mL,and the half inhibitory concentration was 0.05 ng/mL.The cross-reactivity with cefaclor was 111.1%,with ceftriaxone sodium,cefuroxime axetil and cephalotin sodium were all less than 0.1%,respectively.Recoveries of cephalexin from spiked milk at levels of 1,4 and 8 ng/mL were 94.4%,103.3% and 97.5%,respectively.【Conclusion】 The method of surface-enhanced Raman spectroscopy combined with immunochromatography for detecting cephalexin developed in this study was simple,rapid,sensitive and low-cost,which could be used for on-site mass sample screening and testing.

Key words: cephalexin; Au (core)@Ag (shell); surface-enhanced Raman spectroscopy (SERS); immunochromatographic assay