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

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. (C) 2018 Elsevier B.V. All rights reserved.