Optical Detection of Lead and Potassium Ions Using a Quantum-Dot-Based Aptamer Nanosensor

Quantum-dot (QD) based nanosensors can be used to detect a wide range of molecules. This study examined a nanosensor comprised of thrombin binding aptamer (TBA) with 700NC InGaP QD on the 5 ^' terminus and an Au nanoparticle quencher on the 3 ^' terminus. Both K⁺ and Pb²⁺ bind to TBA, resulting in a conformational change that brings the Au quencher closer to the QD. Photoluminescence measurements indicated a decrease in fluorescence corresponding to an increase in either K⁺ or Pb²⁺ concentration. For healthy blood serum K⁺ concentrations (3.5-5 mM), the beacon exhibited 15-17% quenching efficiency. Pb²⁺ concentration of 0.48 μM, the threshold for toxicity in serum, yielded 14% quenching. The beacon's ability to detect changes in ion levels in a critical range of concentrations can make it an effective diagnostic tool.