A nanoparticle-based molecular beacon for directly detecting attomolar small RNA from plasma without purification

Area of Science:

• Biomedical Engineering
• Molecular Diagnostics
• Nanotechnology

Background:

• Traditional molecular beacons (MBs) use fluorescent molecules that suffer from photobleaching and background autofluorescence, limiting detection sensitivity.
• Detecting small RNA biomarkers in complex biological samples like plasma is challenging due to low concentrations and interfering signals.

Purpose of the Study:

• To develop a nanoparticle-based molecular beacon (NPMB) utilizing upconversion nanoparticles (UCNPs) for enhanced detection of small RNA.
• To overcome the limitations of traditional fluorescent probes by employing UCNPs excited by near-infrared light.

Main Methods:

• Designed a DNA hairpin structure incorporating UCNPs as fluorophores and gold nanoparticles (Au NPs) as quenchers.
• Utilized the destruction of the hairpin structure upon target binding to release UCNP fluorescence for detection.
• Employed near-infrared (NIR) excitation to minimize background autofluorescence.

Main Results:

• Demonstrated ultrasensitive detection of a 22-nt microRNA (miR-21) and its complementary DNA in aqueous solutions from aM to pM levels.
• Successfully detected unpurified small RNA (miR-21) in human plasma samples with high sensitivity.
• Achieved an ultra-low background signal due to the unique properties of UCNPs and NIR excitation.

Conclusions:

• NPMBs offer a promising label-free and purification-free method for sensitive detection of small nucleic acid biomarkers.
• The developed NPMB technology enables detection of biomarkers in complex clinical samples with aM-level sensitivity.
• This approach holds potential for improved disease monitoring and diagnostics.