Synthesis of highly fluorescent N,S co-doped carbon quantum dots and their application in fluorometric detection of g-quadruplex forming HER2 promoter region

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Zeynep İrem Bulut - Thesis.pdf

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2022-8

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BULUT, Zeynep İrem

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The human epidermal growth factor receptor 2 (HER2) is a member of HER family which are known to be involved in cell development and differentiation. The overexpression of HER2 is linked to aggressive forms of breast cancer. It has been reported that the formation of a stable parallel G-quadruplex (G4) in the HER2 promoter region was playing a role in the regulation of HER2 expression in MCF-7 cells. Consequently, we hypothesized that the detection of HER2 G4 structure could be used in investigating HER2 expression. Within this thesis, first Nitrogen and Sulfur Co-doped carbon quantum dots (N,S-CQDs) were synthesized using citric acid and L-cysteine and characterized by TEM, DLS, XRD and XPS. Next, fluorescent Thioflavin T (ThT) dye was used as the quencher of N,S-CQDs and N,SCQDs/ThT mixture was used as a probe to detect HER2 G4 structure. The developed probe was found to exhibit a remarkable sensitivity towards HER2 G4 with LOD of 0.22 µM, and LDR of 0.27 µM to 6.0 µM. The probe was also selective towards HER2 G4 among other single-stranded (Poly A, dA32, dT32), double-stranded (dA32dT32), and G4 structures (RB, Pu22, C-MYC, VEGF, BCL-2, and K-RAS) under the optimized conditions. The structure of HER2 G4 and its interactions with N,S-CQDs and ThT were further characterized via Circular Dichroism spectroscopy. To the best of our knowledge, this is the first platform developed for HER2 G4 detection, and we believe it could open up new avenues in fast and routine detection of HER2 G4 structure.

Subject Keywords

Carbon dots, Thioflavin T, Optical properties, Fluorescence detection, HER2 G-quadruplex

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https://hdl.handle.net/11511/99469

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

Z. İ. BULUT, “Synthesis of highly fluorescent N,S co-doped carbon quantum dots and their application in fluorometric detection of g-quadruplex forming HER2 promoter region,” M.S. - Master of Science, Middle East Technical University, 2022.