Lichun Zheng,Xiuhui Liu,Min Zhou,Yongjun Ma,Guofan Wu,Xiaoquan Lu
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.
A new electrochemical biosensor based on the hybridization chain reaction and layered molybdenum selenide (MoSe2) stacked nanorod for dual-signal amplification is developed for the highly sensitive detection of the DNA sequences of Human Immunodeficiency Virus type 1 (HIV-1). The MoSe2 nanorod was prepared using a facile hydrothermal method. The glassy carbon electrode was first modified with MoSe2 nanorods and then Au nanoparticles (AuNPs) were electrodeposited on the electrode. The DNA probe was then immobilized on the electrode by an Au–S bond. As the initiator strands, auxiliary DNA can propagate a chain reaction of hybridization events between the two hairpin probes (Aux 1, Aux 2), and long nicked DNA polymers can be formed on the modified electrode. The biotin-labeled dsDNA polymers can then introduce numerous avidin-labeled horseradish peroxidases on the electrode, resulting in a significantly amplified electrochemical signal through the electrocatalysis of horseradish peroxidase. The target DNA is detected on the basis of the enzymatic oxidization of Fe2+ by H2O2. The electrochemical signals have a good linear relationship with the logarithm of target DNA concentration in the range from 10 fM to 0.1 pM, reaching a detection limit of the target DNA as low as 4.0 fM. This method shows good specificity for target DNA detection with the capability to discriminate single-base-pair mismatched DNA mutations. Moreover, the developed strategy was applied successfully in a real sample, which demonstrated the potential applications in clinical diagnostics.
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