The authors describe an ultrasensitive method for simultaneous detection of neomycin (NEO) and quinolones antibiotics (QNS). It is based on the use of (a) two immuno-nanoprobes (a probe for NEO and a probe for QNS), (b) surface-enhanced Raman scattering (SERS) detection, and (c), a portable lateral flow assay (LFA). The two probes consist of gold nanoparticles (AuNPs) conjugated to the Raman active molecule 4-aminothiophenol (PATP), and to monoclonal antibody against NEO (NEO mAb) or against NOR (NOR mAb). Quantitative detection of NEO and QNS was realized via SERS of the PATP-coated AuNPs captured in the test line of a LFA. Under optimized condition, the visual limits of LFA are 10 ng·mL-1 for NEO and 200 ng·mL-1 for NOR, and with LODs down to 0.37 pg·mL-1 and 0.55 pg·mL-1 by using SERS. The NEO test line is not interfered by the NEO analogues gentamycin, streptomycin and tobramycin, but the NOR test line suffers from different degrees of cross-reactivity (CR) to 12 common other QNS, the CRs ranging from 1.5% to 136%. The recoveries of NEO and NOR from spiked milk samples ranged between 86% and 121%, with relative standard deviations (RSD) from 3% to 6%. The method is highly sensitive, accurate and effective. It may be applied to simultaneous detection of NEO and 8 QNS, including NOR, enoxacin, ciprofloxacin, ofloxacin, fleroxacin, marbofloxacin, enrofloxacin, and pefloxacin. Graphical abstract Schematic of a lateral flow assay (LFA) based on an indirect competitive model. By using two test lines, the LFA can detect the neomycin and quinolones antibiotics simultaneously. Based on the surface-enhanced Raman scattering (SERS), the LFA shows high sensitivity to antibiotics with low limit of detection.
Keywords: 4-aminothiophenol; Affix recovery; Broad-specificity; Cross-reactivity; Gold nanoparticles; Milk analysis; Monoclonal antibody; Optimization; Spectra; Standard curve.