Colorimetric and fluorescence dual-mode detection of oxytetracycline based on hemin/G-quadruplex DNAzyme and ZIF-8

With the gradual increase of oxytetracycline (OTC) residue in the environment, it is particularly important to establish a sensitive and efficient method to detect OTC. In this work, a novel colorimetric and fluorescence dual-mode detection method based on hemin/G-quadruplex (hemin/G4) DNAzyme and zeolitic imidazolate framework-8 (ZIF-8) is developed. OTC can compete with G4 to bind hemin to reduce the amount of hemin/G4. Thus, the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to blue color by hemin/G4 is inhibited. In addition, the OTC or OTC-hemin can be aggregated with the help of ZIF-8 to produce strong green fluorescence due to the aggregation-induced emission (AIE) effect. In colorimetric and fluorescence mode, the linear ranges of the new method are 0.375–18 μM and 0–52.5 μM, with a limit of detection (LOD) of 0.116 μM and 0.040 μM, respectively. Besides, this new method has a good selectivity and recovery rate in the detection of real samples. Therefore, the method can be used for the efficient and sensitive detection of OTC.