Enhanced colorimetric strategy: Aptamer-triggered assembly of Ni-Fe layered double oxide/DNA networks for ultrasensitive detection of chloramphenicol

In this study, a colorimetric assay was designed for ultrasensitive detection of chloramphenicol (CAP). In the presence of CAP, Ni-Fe layered double oxide/DNA networks (Ni-Fe LDO/DNA NWs) can be formed based on the combination of G-quadruplex (G4), DNA and magnetic Ni-Fe LDO nanosheets (NSs). Then, the as-formed Ni-Fe LDO/DNA NWs was applied to catalyze the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) based on the enhanced peroxidase-like catalytic activity for the colorimetric analysis of CAP. To effectively enhanced the detection sensitivity, enzyme-free amplification methods including catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) were employed during this process. In addition, the background signal can be effectively reduced by means of the magnetic separation. Under optimal conditions, this strategy exhibited a wide linear range from 0.1 fM to 0.01 nM (r2 = 0.998), and the limit of detection (LOD) was obtained as 11.6 aM. Furthermore, the high specificity and stability of this strategy allowed its successful application to the quantitative analysis of residual CAP in genuine milk samples.