Fluorine-doped carbon dots (F-CDs) adsorbing DNA via hydrophobic interaction play dual-role of quenching carrier and signal reference for ratiometric fluorescence strategy to detect microRNA

The expression levels of microRNAs (miRNA) can provide insights into the occurrence, progression, and treatment efficacy in tumors, highlighting the need for precise and easily controllable detection methodologies. The reasonable design of carbon dots enables the precise manipulation of luminescence and surface characteristics. Herein, fluorine doped carbon dots (F-CDs) were designed and prepared to establish a reasonable control of the interaction force between DNA and F-CDs. F-CDs were synthesized through a hydrothermal reaction involving tetrafluoroterephthalic acid and tetraethylene pentaamine, resulting in noteworthy optical and amphiphilic properties. F-CDs proficiently interact with single-stranded DNA (ssDNA) through hydrophobic interaction, leading to the quenching of dye labeled ssDNA, while maintaining self-fluorescence stability. The quenching mechanism was elucidated. The complementary DNA sequence induced nearly 100% desorption of ssDNA from F-CDs. Assisted by the target cycling signal amplification from duplex specific nuclease (DSN) and the self-fluorescence of F-CDs, an effective ratiometric strategy utilizing the adsorption system of F-CDs and probe DNA for let-7a was established for detecting let-7a, a critical miRNA in the assessment of tumor development. Under the optimized conditions, this method demonstrated high sensitivity and reproducibility in detecting let-7a with the linear range from 1.0 fM to 10.0 nM and a low limit of detection (LOD) of 3.0 fM. The recovery of let-7a in plasma and the evaluation of let-7a levels in seven cell types underscored the method's potential for efficient applications in monitoring of miRNA levels in real samples.