DNA Framework Nanoruler-Directed Surface Fluorescence Enhancement as a Sensing Platform for MicroRNA Detection

Area of Science:

• Nanotechnology
• Biomolecular Engineering
• Surface Science

Background:

• Surface-enhanced fluorescence occurs when fluorophores are near metallic surfaces due to enhanced electric fields.
• Understanding this enhancement is limited by the lack of precise distance control (nanorulers) between fluorophores and substrates.
• Heterogeneous spacer sizes lead to variable enhancement and poor reproducibility.

Purpose of the Study:

• To develop a nanoruler for precise distance tuning between fluorophores and metallic substrates.
• To elucidate the distance-dependent mechanism of surface fluorescence enhancement.
• To enable sensitive and reproducible detection of biomarkers.

Main Methods:

• Utilized tetrahedral DNA framework (TDF) nanorulers with thiolated vertices for immobilization on a gold (Au) substrate.
• Attached fluorophores to the fourth vertex of TDFs, controlling the fluorophore-substrate distance via TDF size.
• Investigated fluorescence emission efficiency as a function of TDF-controlled distance.

Main Results:

• Demonstrated distance-dependent fluorescence enhancement, peaking at 5-7 nm.
• Observed enhanced and subsequently decreased emission with increasing fluorophore-substrate distance.
• Achieved homogeneous signal enhancement due to the rigid and uniform size of TDFs.

Conclusions:

• The TDF nanoruler strategy precisely controls fluorophore-substrate distance, revealing fluorescence enhancement mechanisms.
• This method enables highly sensitive detection of microRNA biomarkers for prostate cancer (PCa) with a 1 aM limit of detection.
• The TDF nanoruler approach is versatile and applicable to other distance-dependent systems for performance optimization.