Quantum Dot Sensors and Nanoactuators in Living Cells

Abstract

Quantum dots (QDs) are unique probes due to their special properties (brightness, photostability, narrowband emission and broadband absorption), and excellent bio(chemical)compatibility for imaging structures and functions of living cells. When functionalized with ligands, they enable the recognition of specific targets and the tracking of dynamic processes for extended periods of time, detecting biomolecules with a sensitivity extending to the single molecule level.Here we present nanosensors and nanoactuators based on QDs in which the multivalency of the particle plays an essential role in determining the functionality and sensing characteristics of the nanodevices. Two examples are discussed: (i) luminescent pH nanosensing QDs calibrated and measured by FLIM (Fig. A). The underlying process is bidirectional (a novel feature) FRET between the QD and the conjugated sensor with pH-sensitive spectral properties 1 . (ii) nanoactuators consisting of strepatividin QD to which biotinylated alpha-synuclein (AS) has been conjugated (Fig. B). These constructs are very efficient intiators and sensors of AS aggregation in vitro and in live cells 2 .