Design and Characterization of a Singly Labeled Fluorescent Smart Probe for In Vitro Detection of miR-21

Area of Science:

• Biochemistry
• Molecular Biology
• Diagnostics

Background:

• MicroRNAs (miRNAs) play critical roles in biological processes and cancer.
• Accurate detection of specific miRNAs like microRNA-21 (miR-21) is essential for diagnostics.
• Existing detection methods may lack sensitivity, specificity, or simplicity.

Purpose of the Study:

• To develop and validate a sensitive and sequence-specific hairpin smart probe (SP) for detecting miR-21.
• To evaluate the probe's performance in terms of specificity, sensitivity, and kinetics.
• To establish a simple, homogeneous, mix-and-read assay for miR-21 detection.

Main Methods:

• Design of a hairpin smart probe (SP) with a loop complementary to miR-21 and a stem containing a fluorophore and guanine quenchers.
• Assessment of fluorescence quenching in the absence of miR-21.
• Evaluation of fluorescence restoration upon hybridization with miR-21.
• Testing of sequence specificity against single-base mismatch sequences.
• Kinetic studies at room temperature versus 37°C.

Main Results:

• The SP exhibited significant fluorescence quenching at room temperature due to guanine bases.
• Hybridization with miR-21 restored fluorescence, demonstrating specific target binding.
• The SP successfully differentiated miR-21 from sequences with single-base mismatches.
• Hybridization kinetics at 37°C were seven times faster than at room temperature.
• Achieved a limit of detection of 14.0 nM and a limit of quantitation of 46.7 nM.

Conclusions:

• The developed hairpin smart probe is a sensitive and sequence-specific tool for miR-21 detection.
• The assay is a simple, fast, mix-and-read homogeneous method.
• This platform holds potential for adapting to other miRNA detection and diagnostic applications.