Nanokinetics of drug molecule transport into a single cell

Aims: To analyze drug transport at a single cell level, a mast cell line, RBL-2H3, was treated with cell-permeable fluorescent compounds, such as quinacrine, and was monitored by a fluorescence video microscope. Methods: Small areas in the video that corresponded to granules and part of the cytosol in a cell were chosen and the signal intensity in these areas was monitored sequentially. Results: The initial rate of quinacrine uptake through the cell membrane calculated from the fluorescent signal was correlated with quinacrine concentration, and it decreased at a lower temperature, showing that the transport was an energy-requiring process, such as active transport. The kinetics of the transport through the microgranular membrane did not depend on the temperature but the pH in the cytosol, therefore this process should be passive transport by pH gradient. Conclusion: These data indicate that the observation of video microscope-mediated drug transport using fluorescent dye is useful in kinetic analysis at the nanometer scale.