Integrating liquid-phase interfacial SERS ratiometric sensors with biobarcoded nanoparticle probes for on-site sensitive detection of antibiotic residues in food.

A liquid-phase interfacial surface-enhanced Raman scattering (SERS) ratiometric sensor is proposed through integrating with catalytic hairpin assembly (CHA)-engineered biobarcoded nanoparticle probes for sensitive and accurate kanamycin (Kana) detection. In the SERS ratiometric sensors, the Au-MBA@Ag nanoparticles (Au-MBA@Ag NPs) array generated by self-assembly on the hexane-water interface functionalized with Cy5-labeled Cu-specific DNAzyme (Cu-Enz), serving as SERS platform. Kana-driven aptamer specificity recognition followed by CHA-engineered biobarcoded-like copper oxide nanoparticles (CuO NPs) probe, generating a cascade Cu dual-signal amplification. The products of Cu activate DNAzyme, which cleaves the substrate strand on the SERS substrate, bringing the Raman label Cy5 closer to the SERS substrate and generating a strong SERS signal ("on" status). Quantitative detection of Kana is achieved by using the SERS intensity ratio between Cy5 and 4-MBA, which serves as corrective internal standard (IS). Benefiting from the synergistic amplification of CHA and CuO NPs chemical signal amplification, the ratiometric amplifier specifically measures Kana with a sensitivity of 0.003 ng/mL. Compared with solid-phase SERS substrates, ratio-dependent liquid-phase interfacial SERS platforms can effectively enhance the reproducibility and reduce the instability of the signal analysis, enabling to distinguish Kana even from excess coexisting interferences. Significantly, the SERS ratiometric sensors can achieve reliable and accurate detection of Kana in honey, indicating that this method has great potential for practical applications in food analysis.