Monitoring Of Cell-Dependent Reduced States Using Aptamer-Functionalized Reduction-Sensitive Quantum Dots

Conjugation of quantum dot (QD) with oxidized nile blue (NB) is known to be able to strongly decrease fluorescence intensity of QD. In the present study, NB-conjugated QD (QD-NB) was functionalized with anti-human epidermal growth factor receptor 2 aptamer to form aptamer-functionalized QD-NB (Apt-QD-NB), as a new biosensing platform to monitor aptamer-dependent internalizations and reduction-dependent transformations. Our study shows that more QD fluorescence signals in cells can be induced by the specific internalization of higher amounts of Apt-QD-NB and that the higher ratio of reduced NB over oxidized NB resulting from the different reducing environment of the cells can lead to brighter QD signals. Apt-QD-NBs are expected to be used as optical labels that can monitor intracellular metabolic pathways at the single-cell level, because the use of Apt-QD-NBs to investigate drug effectiveness and cellular redox conditions offers exciting opportunities for drug screening.