Ultrasensitive determination of DNA sequences by flow injection chemiluminescence using silver ions as labels

We presented a new strategy for ultrasensitive detection of DNA sequences based on the novel detection probe which was labeled with Ag + using metallothionein (MT) as a bridge. The assay relied on a sandwich-type DNA hybridization in which the DNA targets were first hybridized to the captured oligonucleotide probes immobilized on Fe 3 O 4 @Au composite magnetic nanoparticles (MNPs), and then the Ag + -modified detection probes were used to monitor the presence of the specific DNA targets. After being anchored on the hybrids, Ag + was released down through acidic treatment and sensitively determined by a coupling flow injection–chemiluminescent reaction system (Ag + –Mn 2+ –K 2 S 2 O 8 –H 3 PO 4 –luminol) (FI–CL). The experiment results showed that the CL intensities increased linearly with the concentrations of DNA targets in the range from 10 to 500   pmol   L −1 with a detection limit of 3.3   pmol   L −1 . The high sensitivity in this work may be ascribed to the high molar ratio of Ag + –MT, the sensitive determination of Ag + by the coupling FI–CL reaction system and the perfect magnetic separation based on Fe 3 O 4 @Au composite MNPs. Moreover, the proposed strategy exhibited excellent selectivity against the mismatched DNA sequences and could be applied to real samples analysis.