Yuan-Yuan JIANG,Kun WANG,Chong-Zheng XU,Xiao-Di YANG,Hui-Hui LI
In this work, the glassy carbon electrode modified by alizarin (AR) hybridized with graphene (CRG) and chitosan (CS) was prepared. The AR/CRG-CS electrode exhibited a pair of well-defined reversible redox peaks in 0.1 M phosphate buffer solution (PBS, pH 7.4) with the oxidation peak at −0.573 V and the reduction peak at −0.652 V. It exhibited a two-proton and two-electron redox process and a fast heterogeneous electron transfer rate with the rate constant ( K s ) of 1.69 s −1 using the cyclic voltammetry. Based on the characteristics of alizarin with the decreased current and negative potential shift after binding with human telomere DNA, a sensitive, simple, reliable and stable electrochemical method for the detection of human telomere DNA using the AR/CRG-CS electrode was developed. The electrochemical response showed a linear relationship with DNA concentration in the range of 8.0 × 10 −8 −1.4 × 10 −5 M ( R = 0.9995) with the linear regression equation as Δ I pc (μA) = 8.4860 + 0.5366 C (μmol) and the detection limit ( S/N ) as 2.0 × 10 −8 M.
Red fluorescent G-quadruplex DNA selective organic binding probe is relatively underdeveloped. In the present study, we designed a series of new fluorescent probes that exhibit large Stokes shift (112−131 nm), high quantum yield (up to 0.56), robust against photo-bleaching and high selectivity towards quadruplex structures of c-MYC and telomere DNA with strong binding affinity . The discrimination ability of the probes towards G-quadruplex structures against single-/double-stranded DNA or RNA was investigated by analyzing their structural property with respect to their binding specificity. From the sensing application of the probe targeting pu27, an excellent linear relationship (R 2 = 0.9997) with respect to the pu27- A3 interaction signal was observed. The LOD was found down to 4.0 nM, which is superior to thiazole orange dye. The probe is able to realize real-time fluorescence visualization in aqueous, PAGE staining and live cell imaging. In addition, from the immunofluorescence analysis using the probe and BG4 antibody, the A3 foci and BG4 staining co-localized well in PC3 cells, which suggest that the probe is G-quadruplex selective and is useful for visualizing G-quadruplex DNA structures in live cells. Cytotoxicity assays also demonstrated that the probe has low cytotoxicity against both PC3 cancer cells and 16HBE normal cells.
Human telomere DNA plays a vital role in genome integrity control and carcinogenesis as an indication for extensive cell proliferation. Herein, silver nanoclusters (Ag NCs) templated by polymer and unmodified gold nanoparticles (Au NPs) are designed as a new colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA. Ag NCs can produce the aggregation of Au NPs, so the color of Au NPs changes to blue and the absorption peak moves to 700 nm. While the telomere DNA can protect Au NPs from aggregation, the color turns to red again and the absorption band blue shift. Benefiting from the obvious color change, we can differentiate the length of telomere DNA by naked eyes. As the length of telomere DNA is longer, the variation of color becomes more noticeable. The detection limits of telomere DNA containing 10, 22, 40, 64 bases are estimated to be 1.41, 1.21, 0.23 and 0.22 nM, respectively. On the other hand, when telomere DNA forms G-quadruplex in the presence of K + , or dsDNA with complementary sequence, both G-quadruplex and dsDNA can protect Au NPs better than the unfolded telomere DNA. Hence, a new colorimetric platform for monitoring structure conversion of DNA is established by Ag NCs-Au NPs system, and to prove this type of application, a selective K + sensor is developed.
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