Aptamer-Functionalized Silica Particles for FRET-Based Fluorescence Switching

Area of Science:

• Bioconjugation Chemistry
• Nanomaterials Science
• Biomedical Diagnostics

Background:

• Aptamer-conjugated particles face stability issues like degradation and fluorescence quenching.
• Covalent anchoring of aptamers improves construct integrity over noncovalent methods.
• Existing methods lack modularity and robust fluorescence preservation under physiological conditions.

Purpose of the Study:

• To develop a stable, modular, and fluorescent aptamer-based biosensor.
• To enhance the structural integrity and fluorescence preservation of aptamer-conjugated silica particles.
• To create a Förster resonance energy transfer (FRET)-based fluorescent switch for protein biomarker detection.

Main Methods:

• Covalently anchored azide- and FITC-labeled aptamers onto polyethylenimine (PEI)-coated silica particles (120 ± 5 nm) using click chemistry.
• Introduced alkyne groups onto silica particles via carbodiimide coupling and conjugated aptamers via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC).
• Utilized a black hole quencher (BHQ)-labeled complementary strand to quench FITC emission via FRET, creating a nonemissive state.

Main Results:

• Achieved enhanced structural integrity and fluorescence preservation under physiological conditions.
• Demonstrated a 2.2-fold increase in fluorescence and ~74% fluorescence recovery upon lysozyme binding due to FRET disruption.
• Established a modular FRET-based fluorescent switch with potential for detecting various protein biomarkers.

Conclusions:

• The developed aptamer-conjugated silica particles offer improved stability and fluorescence preservation.
• This modular FRET-based system provides a sensitive platform for target-responsive protein biomarker detection.
• The click chemistry approach represents a novel method for constructing aptamer-based fluorescent biosensors.