Distribution of FITC-labelled siRNA in M1 cellsin vitro. M1 cells were transfected with Lipofectamine 2000-complexed FITC-labelled siRNA. At indicated time-points after transfection cells were harvested and processed for confocal microscopy. Nuclei were stained with DAPI and are shown in blue (left panel), FITC signal is shown in green (right panel). A and B show biodistribution 30 min after transfection, C and D show biodistribution 24 hrs after transfection.