A SERS-based lateral flow immunochromatographic assay using Raman reporter mediated-gap AuNR@Au nanoparticles as the substrate for the detection of enrofloxacin in food samples.

A lateral flow immunochromatographic assay (LFIA) based on surface-enhanced Raman scattering (SERS) for sensitive and specific detection of antibiotic enrofloxacin (ENR) in food samples was developed. 1,4-benzenedithiol (BDT) was selected as the Raman reporter, and the BDT mediated-gap AuNR@Au nanoparticles (NPs) were synthesized, characterized and used as the substrate in SERS-LFIA due to the existence of the anisotropic gold nanorods (AuNRs) and the nano-gap with the high SERS enhancement. AuNRs were prepared, then covered by monolayer BDT. Under reduction condition and in presence of HAuCl, the reduced gold was deposited and grown on AuNRs to form AuNR@Au NPs. As the two thiol groups on para-positions in BDT were respectively linked to AuNR (core) and Au (shell), the gap size inside the NPs was uniform. The immunoprobe (e.g. AuNR@Au-Ab) was obtained by immobilizing Ab against ENR on the surface of AuNR@Au NPs. The performance of SERS-LFIA was similar to that in colloidal gold based-LFIA, and the entire assay time was within 15 min. After LFIA procedures, the specific SERS intensity of BDT at 1560 cm on the test line was measured for the quantitative detection of ENR. The IC and limit of detection (LOD) of the LFIA for ENR were 59 pg mL and 0.12 pg mL (e.g. 71 pg g and 0.14 pg g in real sample), respectively. There was no cross-reactivity (CR) of the LFIA with other five antibiotics. The recoveries of ENR from spiked food samples were in range of 89.2%-102.4% with the relative standard deviation (RSD) of 1.70%-6.38%. It was proven that the proposed method was able to simply and rapidly detect ENR in food samples with high sensitivity, specificity, accuracy and precision. The platform can be also an alternative platform for the detection of other target analytes using corresponding Abs.