Analytical and Bioanalytical Chemistry

, Volume 399, Issue 8, pp 2763–2770

Label-free detection of nucleic acids by turn-on and turn-off G-quadruplex-mediated fluorescence

Original Paper

Abstract

In this study we have used two fluorescent probes, tetrakis(diisopropylguanidino)-zinc-phthalocyanine (Zn-DIGP) and N-methylmesoporphyrin IX (NMM), to monitor the reassembly of “split” G-quadruplex probes on hybridization with an arbitrary “target” DNA. According to this approach, each split probe is designed to contain half of a G-quadruplex-forming sequence fused to a variable sequence that is complementary to the target DNA. Upon mixing the individual components, both base-pairing interactions and G-quadruplex fragment reassembly result in a duplex–quadruplex three-way junction that can bind to fluorescent dyes in a G-quadruplex-specific way. The overall fluorescence intensities of the resulting complexes were dependent on the formation of proper base-pairing interactions in the duplex regions, and on the exact identity of the fluorescent probe. Compared with samples lacking any “target” DNA, the fluorescence intensities of Zn-DIGP-containing samples were lower, and the fluorescence intensities of NMM-containing samples were higher on addition of the target DNA. The resulting biosensors based on Zn-DIGP are therefore termed “turn-off” whereas the biosensors containing NMM are defined as “turn-on”. Both of these biosensors can detect target DNAs with a limit of detection in the nanomolar range, and can discriminate mismatched from perfectly matched target DNAs. In contrast with previous biosensors based on the peroxidase activity of heme-bound split G-quadruplex probes, the use of fluorescent dyes eliminates the need for unstable sensing components (H2O2, hemin, and ABTS). Our approach is direct, easy to conduct, and fully compatible with the detection of specific DNA sequences in biological fluids. Having two different types of probe was highly valuable in the context of applied studies, because Zn-DIGP was found to be compatible with samples containing both serum and urine whereas NMM was compatible with urine, but not with serum-containing samples.

Keywords

G-quadruplex Conformational constraint Split probe Fluorescent probe 

Supplementary material

216_2011_4669_MOESM1_ESM.pdf (124 kb)
ESM 1(PDF 123 kb)

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied ChemistryChinese Academy of ScienceChangchunChina
  2. 2.Graduate School of Chinese Academy of ScienceBeijingChina
  3. 3.Institute of Organic ChemistryUniversity of ZürichZürichSwitzerland
  4. 4.Department of Chemistry and PhysicsState University of New York at Stony BrookNew YorkUSA

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