Probing the Tl+-induced structural transformation of G-rich DNA to G-quadruplex with a label‐free thioflavin T-based biosensor

• Published in: Sensors and actuators. B, Chemical Vol. 378; p. 133210
• Main Authors: Dong, Zhen, Xie, Chengxia, Li, Xianming, Wu, Peng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2023
• Subjects: Fluorescent biosensor; G-quadruplex; Thioflavin T; Toxicity of Tl; Toxicity of Tl; Fluorescent biosensor; Thioflavin T; G-quadruplex
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2022.133210

More than 700,000 G-rich sequences in the human genome are able to form G-quadruplex (G4). Since G4 is closely relevant to a variety of essential biological regulatory processes, identification of these G-rich DNAs (G-rich → G4) is thus important for DNA-involved interactions, e.g., metal ions and small molecules. Circular dichroism (CD) and NMR are the dominated tools for studying G4 DNA-based interactions, but suffers from low sensitivity. Herein, with toxic Tl+ as the model inducer, we demonstrated that thioflavin T (ThT), a typical label-free G4 dye, could be explored for highly sensitive probing of Tl+-induced structural transformation of G-rich DNAs to G4. With several model G4-forming DNAs, it was found that the Tl+-induced CD spectra developments correlated well with its fluorescence modulation on ThT (ThT-DNA → ThT-DNA-Tl+). In other words, the Tl+-induced structural change (Free State → G4) could be well probed with the ThT fluorescence change. For typical non-G4-forming DNAs, no appreciable ThT fluorescence modulation was received. To further increase the accuracy of picking up G4-forming DNAs from unknown samples, the photophysical parameters (absorption, fluorescence emission, and fluorescence lifetime) change of ThT before and after Tl+ modulation were integrated to develop a two-step linear discrimination analysis (LDA) protocol, with cross-validation accuracy of over 90%. After picking up G4-forming DNAs from the unknown samples, the Tl+-induced structural transformation of G4 DNAs could be thus evaluated. [Display omitted] •A G-quadruplex-based label-free fluorescent biosensor for probing of the G-quadruplex-involved interactions.•Much higher sensitivity of ThT-based fluorescent biosensor as compared with CD detection.•For unknown samples, first picking up G4 DNAs and then evaluating the Tl+-induced structural transformation of G4 DNAs.