(733c) Selective Intracellular Labeling Using Microfluidic Electroporation-Delivered Quantum Dots

Quantum dots (QDs) are luminescent semiconductor nanocrystals that have extraordinary brightness and exceptional photostability. Due to these superiorities, QDs have been widely used as a replacement of organic dyes as fluorophores for studying cell biology, particularly in long-term observation and single particle tracking.  However, QDs without specific coating are unable to penetrate the cell membrane due to their size and surface properties. Currently, QDs with cell penetrating coating are mostly used for delivering, which cause the encapsulation of QDs in endosomes. Microinjection is a way to overcome this restriction, but it requires single cell manipulation and complicated operation which results in a very limited throughput. Our studies revealed that electroporation deliveries QDs into cells with high efficiency and these QDs are available for subcellular targeting and tracking.

In our project, we used electroporation as an efficient method for QDs delivery and intracellular targeting in microfluidic devices. Electroporation has been commonly used for gene transfer and drug delivery in vitro and in vivo. Microfluidic chips provide us convenient platform for culturing, operating and viewing cells, as well as conducting in vitro electroporation. Several groups have reported the delivery of QDs by electroporation, but no systematical research has been conducted. Furthermore, no study of intracellular targeting with electroporation-delivered QDs has been conducted. We demonstrated that electroporation deliveries QDs into cells independent of endocytosis, and their distribution within the cytoplasm is homogeneous. We also systematically studied, characterized and optimized the microfluidic electroporation conditions for QDs delivery and cell viability. With cytosolic dispersed QDs that have been conjugated with anti-kinesin antibody, we were able to visualize the dynamic motion of intracellular kinesin, which is a linear motor protein supports transportation of cellular cargo. We believe this is the first tracking of endogenous molecules in living cells with microfluidic electroporation-delivered QDs. Hence, our results indicate that electroporation may serve as a powerful tool to delivery antibody coated QDs into cells for single molecular tracking within living cells.