Visual detection of G-quadruplex with mushroom derived highly fluorescent carbon quantum dots

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Abstract

G-quadruplexes are secondary DNA structures frequently found in telomeres and DNA sequences related to gene regulation, etc. Herein, we report a label free, sensitive and visually detectable fluorescence based biosensing platform for the detection of G-quadruplexes in DNA. Highly fluorescent N-doped carbon quantum dot (CD) with enriched functional groups was synthesized from Ganoderma lucidum, an oriental fungus by using a green hydrothermal process. Noncovalent functionalization of CD was done with Hemin where Hemin/CD conjugate forms a quenched union. However, in presence of DNA sequences that contain G-quadruplexes, the fluorescence of CD is restored selectively. The fluorescence restoration of CD is attributed to the stripping of Hemin from Hemin/CD conjugate that preferably slide into the G quadruplexes leaving CD. This increase in CD fluorescence is easily detectable under hand-held UV light without any other instrumental intervention for G-quadruplex containing DNA only and not in any other DNA samples. Also, such selective fluorescent recovery was not observed with chemically synthesized CD that lack hydroxyl functionality.

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