Zen light software

Migration devices were passivated with 30 mg/mL BSA in PBS at 4°C overnight to reduce absorption of fluorescently labeled dextran to the PDMS surface. Prior to imaging, the BSA solution was replaced with PBS on the side the cells are loaded on and Texas Red–labeled 70-kDa dextran (Molecular Probes) dissolved at 10 mg/ml in PBS (Invitrogen) on the other side, mimicking the conditions for the migration experiments with a PDGF gradient. The devices were then covered with a glass coverslip to minimize evaporation, placed on the heated microscope stage or in a temperature controlled incubator and imaged at defined time-points for up to 24 hours. Line profiles of the fluorescence intensity were obtained using Zen light software (Zeiss) and the average profiles from at least 3 different measurements at each time point were used to determine the time course and stability of the gradient formation reported in Figure 1. As the PDGF used for the migration experiments has an even lower weight (~25 kDa) than the fluorescently labeled dextran, it is expected that the PDGF gradient forms even faster than the data presented in Figure 1.