Colorimetric determination of tetracyclines based on aptamer-mediated dual regulation of gold nanoparticle aggregation and in situ silver metallization

Abstract

A colorimetric assay was described for determination of tetracyclines (TCs) in complex matrices based on dual regulation of gold nanoparticle (AuNP) aggregation and in situ silver metallization. The reaction between p-aminophenol and silver ions (Ag⁺) catalyzed by aptamer (Apt)-functionalized AuNPs promoted the in situ deposition of Ag shells on AuNPs to afford core–shell bimetallic NPs (Au@AgNPs). When the target is present, Apt is separated from the AuNP surface through the Apt-target interaction. With the desorption of Apts, AuNPs catalyzed the formation of more aggregated Au@AgNPs with a thinner Ag shell, corresponding to the solution color gradually changing from orange-yellow to brown. Using A₆₀₀/A₄₁₀ as the determination signal, the assay gave visible linear relationships for TCs in the range of 0.3–6.0 μmol L⁻¹ with a detection limit (LOD) of 33.6 nmol L⁻¹. In particular, the assay was successfully applied to detect TCs in real samples with the recovery rate ranging from 91.2% to 106% and relative standard deviation (RSD) less than 4.6%. These results meet the requirements of sample analysis.