The invention provides
ion-selective sensors comprising
quantum dots capable of selectively measuring ions, e.g., Na+, K+, Cl−, etc., in various environments, including in the
cytosol of a
living cell.
Quantum dots are attractive probes for
microscopy due to their photophysical advantages over fluorescent dyes, including prolonged photostability, brightness and
quantum efficiency. In certain embodiments, a sensor comprises one or more
quantum dots, a pH-sensitive dye, and optionally an
ion-selective component such as an
ionophore. These elements may, for example, be disposed in a
polymer matrix. In certain embodiments, the sensors may detect ionic analytes by selective
ion extraction by the
polymer, thereby inducing a pH change within the sensor which in turn changes the
absorbance of the pH-sensitive dye. The change of
absorbance may in turn attenuate the intensity of detectable emissions, e.g.,
fluorescence, from the
quantum dot by directly absorbing its
fluorescence emission.