Research on the interaction mechanism between quantum dots and radionuclides for the improvement of Cerenkov luminescence imaging

Cerenkov luminescence imaging (CLI) is a relatively new optical molecular imaging technique. The nature of Stokes shift in quantum dots (QD) can be used to improve the quality of CLI. However, the interaction mechanism of QD with Cerenkov light remains unclear. In this work, the interaction mechanism between QD and radionuclides emitting β rays, γ rays, and Cerenkov light was investigated. The 96-well plates were used to test the different levels of radioactivity of radionuclides with different QD concentrations. Transparent vials were used to determine the relationship between QD fluorescence intensity and the distance from QD to the radionuclide. In addition, black paper was used to block the transmission of Cerenkov light through the QD vials. A linear relationship was found between the number of photons and the radioactivity of radionuclides when the QD concentration was kept constant. Similarly, the number of photons was linearly related to the QD concentration when the radioactivity of radionuclides was kept constant. Furthermore, with the increases in the distance between radionuclides and quantum dots, the number of photons was exponentially decreased. Meanwhile, the number of photons emitted from QD excited by Cerenkov light accounted for 20% the total number of photons excited by 131I radionuclide. The result proved that QD was not only excited by Cerenkov light but also by other rays.