Microchimica Acta

, 186:132 | Cite as

A carbon dot and molecular beacon based fluorometric sensor for the cancer marker microRNA-21

  • Mohamad MahaniEmail author
  • Zhahra Mousapour
  • Faten Divsar
  • Alireza Nomani
  • Huangxian Ju
Original Paper


A carbon quantum dot (CQD) labeled molecular beacon was synthesized and applied to the detection of microRNA-21. The CQDs possess low cytotoxicity, excellent water solubility, and photostability. The CQDs were characterized by transmission electron microscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, and fluorescence spectroscopy. The molecular beacon (MB) was labeled with the CQDs at the 5′ end, and with Black Hole Quencher 1 (BHQ1) at the 3′ end. The two labels act as the donor and acceptor parts of a FRET system, respectively. Only weak fluorescence is observed in the absence of microRNA-21, and in the presence of scrambled or mismatched sequences. However, in the presence of microRNA-21, fluorescence intensity of the CQDs at 460 nm (excitation at 360 nm) recovers. The hybridization of the hairpin structure of the MB with microRNA-21 opens the loop of MB. Consequently, the distance between the BHQ1 quencher and the CQDs is increased and fluorescence changes. The probe has high sensitivity (with a 0.3 nM limit of detection) and specificity. It can distinguish between microRNA-21 and its single mismatch mutant and hence represents a valuable tool for the early cancer diagnosis.

Graphical abstract

Schematic presentation of a fluorometric microR-21 assay using carbon dots carrying a molecular beacon (MB) labeled with a black hole quencher. Quenching is suppressed once the MB binds to microRNA-21.


Carbon quantum dots Cancer detection FRET Fluorescence biosensor BHQ1 quencher Hairpin Thermodynamic analysis 


Compliance with ethical standards

The author(s) declare that they have no competing interests.

Supplementary material

604_2019_3233_MOESM1_ESM.docx (274 kb)
ESM 1 (DOCX 274 kb)


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Chemistry, Faculty of Chemistry and Chemical EngineeringGraduate University of Advanced TechnologyKermanIran
  2. 2.Department of Nanotechnology, Faculty of Sciences and Modern TechnologiesGraduate University of Advanced TechnologyKermanIran
  3. 3.Department of ChemistryPayame Noor UniversityTehranIran
  4. 4.Department of PharmaceuticsRutgers, The State University of New JerseyPiscatawayUSA
  5. 5.State Key Laboratory of Analytical Chemistry for Life Science, Department of ChemistryNanjing UniversityNanjingChina

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