(681b) Tracking Nanoparticle Uptake Into Cells by Total Internal Reflection Fluorescence Flow Cytometry

Study of kinetics of initial nanoparticle uptake into cells through plasma membrane presents a challenge for current techniques. Total internal reflection fluorescence (TIRF) microscopy is able to track the transport of nano-scale particle/molecules within ~100 nm depth of the cell plasma membrane for investigating exocytotic release, endocytosis and the dynamic interaction and binding between ligands and membrane bound receptors. However, it is always limited by the number of cells that it interrogates. Furthermore, the requirement for cell adhesion makes it unsuitable for non-adherent cells. Here we develop TIRF flow cytometry (TIRF-FC) as a high-throughput tool to quantitatively study cellular uptake of nanoparticles without imaging. Quantum dots (QD) coated with TAT peptide were assembled and delivered to Chinese Hamster Ovary (CHO) cells. This endocytosis processed was studied by TIRF-FC presented by histograms at various incubation periods with a throughput of 150~250 cells/s. We were able to quantify the fluorescence intensity close to plasma membrane, inferring the distance of QD from the membrane during endocytosis process. A constant translocation rate is found, which is highly consistent with other researches based on single molecule detection technique.