Quantum-Dot-Based Aptamer Beacon for the Detection of Potassium Ions

Monitoring serum potassium ion levels is very common in blood tests, for abnormal potassium ion levels are usually signs of many disease such as hyper blood pressure. This study reports the first use of quantum dot (QD)-based-aptamer beacons for the detection of potassium ion concentrations. In this paper, the detection of changes in potassium versus the fluorescence intensity of the beacon is obtained. In addition, for the same aptamer sequence, one with a six-base spacer and one without the spacer are also compared. The photoluminescence measurements indicate that beacons with six-base spacers exhibit a better on-off contrast due to a longer separation between QDs and the quenchers. Dissociation constants of the aptamer probes against potassium ions are also obtained. The large on-off contrast, which can be seen by the naked eye, points to the potential of the development for take-home potassium ion level sensor devices.