Efficient SERS Substrate HOF@Au in Conjunction with DNAzyme-Mediated DNA Walker as a Signal Amplifier for the Ultrasensitive Detection of Lomefloxacin.

Lomefloxacin (LOM) is an efficacious antibiotic that might lead to liver damage and other adverse reactions if consumed over an extended period. Hence, this study proposed a DNAzyme-mediated DNA walker as a signal amplifier in combination with a substantial quantity of Au nanoparticle (NP)-loaded hydrogen-bonded organic frameworks (HOFs) as a surface-enhanced Raman scattering (SERS) substrate to accomplish the highly sensitive detection of LOM in food. Crucially, due to their high specific surface area and strong adsorption capacity, HOFs act as an ideal substrate for the in situ growth of a large amount of Au NPs, which exhibit a robust and uniform SERS enhancement. Once the target LOM was presented, the DNAzyme was activated to start the DNA walker and produce single DNA in abundance, which further triggered the catalytic hairpin assembly (CHA) cycle. In addition, the multi-interstitial core-shell structure of Au@Ag@4-nitrobenzenethiol (4-NTP)@Au@Hp3 produced more SERS "hot spots" and significantly amplified the local electromagnetic field, with HOF@Au synergistically strengthening the Raman signal of 4-NTP. Using this principle, this sensor achieved the ultrasensitive detection of LOM through the "signal on" strategy, with a detection limit as low as 4.62 × 10 mol/L. This strategy explored a meaningful innovative path for the design of a novel SERS biosensor for the sensitive and selective detection of antibiotics in food.