Optical detection of lead and potassium ions using a quantum-dot-based aptamer nanosensor

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Analytical Chemistry

Background:

• Quantum dots (QDs) are versatile nanomaterials for molecular detection.
• Nanosensors offer high sensitivity and specificity for biological analytes.
• Thrombin binding aptamer (TBA) can be functionalized for ion-specific binding.

Purpose of the Study:

• To design and evaluate a QD-based nanosensor for detecting K+ and Pb2+ ions.
• To investigate the conformational changes of TBA upon ion binding and their effect on QD fluorescence.
• To assess the nanosensor's potential as a diagnostic tool for critical ion concentrations.

Main Methods:

• Fabrication of a nanosensor using 700NC InGaP QD and an Au nanoparticle quencher conjugated with TBA.
• Utilizing photoluminescence measurements to quantify fluorescence quenching.
• Testing the nanosensor with varying concentrations of K+ and Pb2+ in simulated serum samples.

Main Results:

• A conformational change in TBA upon K+ or Pb2+ binding brought the Au quencher closer to the QD, reducing fluorescence.
• The nanosensor demonstrated a dose-dependent decrease in fluorescence with increasing K+ or Pb2+ concentrations.
• Effective quenching efficiencies of 15-17% for physiological K+ levels and 14% for toxic Pb2+ levels were observed.

Conclusions:

• The QD-based nanosensor effectively detects clinically relevant concentrations of K+ and Pb2+ ions.
• The sensor's ability to quantify ion levels in critical ranges highlights its potential as a diagnostic tool.
• This aptamer-functionalized QD nanosensor represents a novel approach for ion detection in biological samples.