A novel fluorescent nanoprobe that based on poly(thymine) single strand DNA-templated copper nanocluster for the detection of hydrogen peroxide.

In this paper, a label-free fluorescence nanoprobe is constructed based on poly(thymine) single strand DNA-templated Copper nanocluster (denote as: T-CuNCs) for the detection of hydrogen peroxide. In the assay, the fluorescent T-CuNCs will generate though the reaction of Cu2+, poly(thymine) and sodium ascorbate. However, the hydroxyl radical (.OH) will generated in the presence of H2O2, which is able to induced the oxidative lesions of poly(thymine) single chain DNA and lead to the poly(thymine) being splitted into shorter or single oligonucleotide fragments and lose the ability to template the fluorescent T-CuNCs again. Therefore, H2O2 can be detected by monitoring the fluorescence strength change of T-CuNCs. The experimental results show that the fluorescence intensity change of T-CuNCs has fantastic linearity versus H2O2 concentration in the range of 1-30 µM (R2 = 0.9947) and 30-80 µM (R2 = 0.9972) with the limit of detection (LOD) as low as 0.5 µM (S/N = 3). More important, the fluorescent nanoprobe was also successfully utilized on the detection of H2O2 in serum samples. Therefore, a label-free, costless and effective fluorescence method has been established for the detection of H2O2, the intrinsic properties of the nanoprobe endow its more potential applications in chemical and biological study.

Magnetic immunoassay using CdSe/ZnS quantum dots as fluorescent probes to detect the level of DNA methyltransferase 1 in human serum sample.

BACKGROUND: DNA methyltransferase 1 (DNMT1), a dominant enzyme responsible for the transfer of a methyl group from the universal methyl donor to the 5-position of cytosine residues in DNA, is essential for mammalian development and closely related to cancer and a variety of age-related chronic diseases. DNMT1 has become a useful biomarker in early disease diagnosis and a potential therapeutic target in cancer therapy and drug development. However, till now, most of the studies on DNA methyltransferase (MTase) detection have focused on the prokaryote MTase and its activity. METHODS: A magnetic fluorescence-linked immunosorbent assay (FLISA) using CdSe/ZnS quantum dots as fluorescent probes was proposed for the rapid and sensitive detection of the DNMT1 level in this study. Key factors that affect the precision and accuracy of the determination of DNMT1 were optimized. RESULTS: Under the optimal conditions, the limit of detection was 0.1 ng/mL, the linear range was 0.1-1,500 ng/mL, the recovery was 91.67%-106.50%, and the relative standard deviations of intra- and inter-assays were respectively 5.45%-11.29% and 7.03%-11.25%. The cross-reactivity rates with DNA methyltransferases 3a and 3b were only 4.0% and 9.4%, respectively. Furthermore, FLISA was successfully used to detect the levels of DNMT1 in human serum samples, and compared with commercial enzyme-linked immunosorbent assay (ELISA) kits. The results revealed that there was a good correlation between FLISA and commercial ELISA kits (correlation coefficient r=0.866, p=0.001). The linear scope of FLISA was broader than ELISA, and the measurement time was much shorter than ELISA kits. CONCLUSION: These indicated that the proposed FLISA method was sensitive and high throughput and can quickly screen the level of DNMT1 in serum samples.