Understanding FRET in Upconversion Nanoparticle Nucleic Acid Biosensors

Area of Science:

• Nanotechnology
• Biochemistry
• Analytical Chemistry

Background:

• Upconversion nanoparticles (UCNPs) are widely used in Förster resonance energy transfer (FRET) bioassays.
• Limited understanding exists regarding surface coatings, bioconjugation, and dye-surface distance effects on UCNP-based FRET biosensing.

Purpose of the Study:

• Investigate the influence of surface coatings (silica, poly(acrylic acid)) and dye-surface distance on UCNP-to-dye FRET DNA-hybridization assays.
• Optimize FRET biosensing performance for enhanced sensitivity and reliability.
• Develop a microRNA detection assay based on optimized UCNP-FRET principles.

Main Methods:

• Utilized NaYF4:Yb3+,Er3+ UCNPs (approx. 24 nm) coated with silica (SiO2) or poly(acrylic acid) (PAA).
• Performed UCNP-to-dye FRET DNA-hybridization assays in H2O and D2O.
• Analyzed photoluminescence (PL) intensity changes and decay times.
• Investigated direct bioconjugation of DNA to PAA coatings.

Main Results:

• FRET exhibited strong distance-dependent photoluminescence intensity changes.
• PL decay times remained largely unaffected due to continuous Yb3+-to-Er3+ energy migration during Er3+-to-dye FRET.
• Optimal FRET performance was achieved with direct DNA bioconjugation to PAA and the closest dye-surface distance, minimizing water quenching.
• A microRNA (miR-20a) FRET assay was developed with a limit of detection of 100 fmol in 80 μL.

Conclusions:

• Surface properties and dye proximity significantly impact UCNP-FRET biosensing.
• Direct bioconjugation to PAA coatings offers an effective strategy for enhancing FRET efficiency.
• Optimized UCNP-FRET assays provide a sensitive platform for microRNA detection.