Quantum Dot Probes for Bioimaging
Single molecule imaging or single cell tracking in vivo requires high quality fluorescent probes that are bright, photo-stable, and compact. The probes also need to have narrow emission profiles (color purity) for sensitive multi-color imaging. Semiconductor nanocrystals, known as quantum dots (QDs), have unique optical and electronic properties that make them ideal for this application. We are developing new synthetic methods to prepare high quality QDs that emit in the visible to near-infrared. We engineer both the inorganic and organic components of QDs to optimize interaction and transport in complex biological systems.
Systematic Synthetic Methods for High Quality QDs
For single molecule imaging, QDs having exceptional structural and optical qualities are required so that a single QD stably produces high fluorescence signals. Despite the extensive studies on QD synthesis, no standardized methods yet exists to generate high quality QDs. Instead, the optimal reaction condition for each QD system is identify mostly by trial-and-error. We develop a library of precursors for systematic synthesis of defect-free quantum dots. We also seek to understand the relationship between the structural and optical properties of quantum dots, and optimize the surface properties for single-molecule detection.
Ligand Engineering and Live Cell Imaging
We also develop strategies to passively deliver QDs into cells and enable single molecule tracking during live cell imaging. To drive QD diffusion into the cytosol, we engineer their ligands to impart them with desired hydrophobicity/hydrophilicity, charge, functional groups, etc.