Au-Ag alloy nanourchins as a highly efficient SERS tag synergistically with MOF@Au for the ultrasensitive detection of oxytetracycline.

Oxytetracycline (OTC) is a potent bactericide, prolonged ingestion may result in hepatic injury and other adverse reactions. Therefore, this study proposed an Au-Ag alloy nanourchins synergistically with layered metal-organic framework (MOFs)@Au as SERS substrate to achieve highly sensitive analysis of OTC in food. Firstly, Au-Ag alloy nanourchins@toluidine blue (TB) combined with Hp2 (AAA-NUs@TB@Hp2), as high-efficiency SERS signal tags, were synthesized to produce a strong Raman signal due to the abundant tips. Besides, layered metal-organic frameworks (MOFs) with a high specific surface area can effectively immobilize substantial quantities of Au NPs and HP1 (MOF@Au@Hp1) and served as SERS substrate, thereby enhancing the sensitivity and uniformity of the sensor. At this time, the absence of the OTC hindered the binding between AAA-NUs@TB@HP2 and MOF@Au@Hp1, resulting in a negligible Raman signal. In the presence of the OTC, the enzyme-free dual-cycle amplification strategy based on entropy-driven DNA reactions and catalytic hairpin assembly (CHA) was activated, resulting AAA-NUs@TB@Hp2 associated with MOF@Au@Hp1, which could significantly amplify the local electromagnetic field and synergistically boosted the TB Raman signal. By this principle, The biosensor exhibited high sensitivity to OTC with a detection limit as low as 6.97 × 10-15 mol/L, which hold significant promise for antibiotic detection in food.