Kinetics of QD655-COOH uptake by MCF-7 cells. Images were taken every 20 min during 40 h of incubation using a live cell microscopy. a. Representative microscopic flat field images at specific time-points indicated. b. Three-dimensional graphs showing intracellular fluorescence intensity of the imaged area at 1 h and 40 h of incubation. The fluorescence intensity was corrected by subtracting background fluorescence as determined from cell-free areas of the region of interest. c. Plot of intracellular fluorescence intensity of the region of interest over time. Blue dots are fluorescence intensity at each timepoint; the straight line is linear regression.