Amplified broad-spectrum detection of tetracyclines in surface water using CdTe@PVP@ZIF-8-accelerated cation exchange reactions and TMSDR-driven self-protective DNAzyme

Abstract

Tetracyclines (TCs) are important in animal husbandry, aquaculture and medical fields, which pose environmental residues and potential health risks. Consequently, the detection of TCs is important for environmental safety. However, traditional detection methods are time-consuming and laborious, and the sensitivity needs to be improved. Accordingly, it is necessary to establish a highly specific and accurate approach for the detection of TCs. Herein, based on CdTe@PVP@ZIF-8 material, a fluorescent biosensor combined with self-locking allosteric hypersensitive DNAzyme (SAH-Dz) was developed for the broad-spectrum detection of TCs in surface water. During the detection process, TCs first bind to the aptamer to activate the toehold-mediated strand displacement reaction (TMSDR), which generates a large amount of P. Subsequently, the binding region of SAH-Dz can change the self-locking conformation by complementary pairing with the base of P, release the DNAzyme binding arm, bind to the substrate chain H, cleave the rA site in the presence of Mg²⁺ , and release Ag⁺ diffusing into the porous ZIF-8. Cation exchange reactions (CER) occur between Ag⁺ and CdTe QDs, inducing fluorescence quenching. The extent of the fluorescence signal's weakening is utilized for the quantitative determination of TCs concentrations. Under optimized conditions, the detection limit of this method for TCs reached 0.0987 nM. This method can achieve sensitive, specific and broad-spectrum detection of four TCs, and is suitable for the identification of antibiotics in surface water.