Carbon Dots Based Fluorescence Nanoprobe for Cell Imaging and Single Particle Tracking

School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 Advances in real-time imaging in living cells have enabled tracking of individual molecules over time and space. Single particle tracking (SPT) technique enables the imaging and mapping of functional biomolecules directly in living cells at unprecedented spatial and temporal resolution [1-4]. This technique has provided a powerful tool to reveal the dynamic structure-function relationships in complex biological systems and dramatically advanced the fundamental understanding of biological systems and medical diagnose [5-7]. The fluorescent probe, which tags the molecules of interest and allows the fluorescent emission, is crucial for intercellular imaging. The considerable interest in intercellular trafficking sparked sustained research efforts on developing of fluorescent probes with high quantum yield, excellent stability and biocompatibility. Carbon dots (CDs) exhibit controlling size and shape, surface heteroatom doping, tunable photoluminescence (PL) and efficient multiphoton up-conversion. These CDs exhibit excellent biocompatibility, high photostability, enhanced brightness and high quantum yields [8]. Therefore, CDs will provide a new platform as versatile probes for single particle tracking (SPT) in various biological and medical areas. In our previous studies [9-10], we synthesis the CDs with optimized remarkable quantum confinement effect, surface effect and surface defect state are expected to present (1) low cytotoxicity and excellent biocompatibility. (2) Capability of precisely controlling the functional-group and feasible labeling of biomolecule for enhanced specificity. (3) Enhanced optical properties. (4) High stability. The CDs are highly chemically and thermally stable. We found that the endosome escape most probably because that the untreated surface group of CDs could provide high buffering capacity to trigger the osmotic swelling and physical rupture of the lysosomes in acid vesicle [9]. This technology can be easily extended to the mobility of molecules and proteins in the cell membrane with the same principle. This new technology will be a major breakthrough of real-time, high resolution of intercellular imaging.