Subnanomolar FRET-Based DNA Assay Using Thermally Stable Phosphorothioated DNA-Functionalized Quantum Dots

Area of Science:

• Nanotechnology
• Biotechnology
• Analytical Chemistry

Background:

• Quantum dots (QDs) offer excellent optical properties for Förster resonance energy transfer (FRET) DNA assays.
• Nonspecific DNA adsorption and poor colloidal stability of QDs hinder assay sensitivity and specificity.
• Stabilizing the DNA/QD interface is crucial for practical QD-based biosensing.

Purpose of the Study:

• To develop a subnanomolar FRET assay for DNA detection.
• To enhance the colloidal stability and specificity of QD-based DNA assays.
• To investigate the role of ligand design in QD surface stabilization for biosensing.

Main Methods:

• Synthesized CdTe/CdS QDs with in situ DNA functionalization using phosphorothioated single-stranded DNA (pt-ssDNA) as a multivalent ligand.
• Assessed colloidal stability and photoluminescence (PL) properties of QD-DNA conjugates at elevated temperatures.
• Evaluated assay sensitivity and specificity using the limit of detection (LOD) and target sequence recognition.

Main Results:

• pt-ssDNA-functionalized QDs exhibited enhanced colloidal stability and maintained PL properties at 70 °C.
• Achieved a >30-fold improvement in sensitivity, with an LOD of 0.47 nM compared to 16.1 nM for conventional QDs.
• Demonstrated high specificity to target DNA sequences, preventing false positives due to nonspecific adsorption.

Conclusions:

• Multivalent ligand design, specifically pt-ssDNA, effectively stabilizes the DNA/QD interface in aqueous solutions.
• Stabilized QD surfaces are critical for achieving high sensitivity and specificity in DNA assays.
• This approach significantly advances the performance of QD-based FRET biosensing platforms for DNA detection.