Figure 6. Platelets adhere faster and in greater numbers to fibrinogen under flow after G7-NH₂ dendrimer treatment.

Platelets were left untreated or stimulated with thrombin (0.5 U/mL) or G7-NH₂ dendrimer (100 μg/mL) for five minutes and flowed at 200 s⁻¹ for six minutes over Ibidi 0.4 VI plates pre-coated with 0.5 mg/mL fibrinogen. In some experiments, platelets were fluorescently labeled before treatment. Images were captured in real-time using an Olympus wide-field fluorescent microscope (IX-81 inverted microscope system) using an ORCA-ER monochrome CCD camera (frame rate 1Hz). Still images from the final frame are depicted in panel A from a single experiment, representative of twelve independent experiments. Images in panel B are still images from the final frame from one experiment, representative of six independent experiments. The flow direction is indicated by the arrow in the upper left hand corner (A, B). The DIC image has been enlarged by 250% in the right panels to show platelet morphology. The initial rate of platelet adhesion and average area covered by platelets were significantly (p<0.05) increased for dendrimer-treated platelets relative to untreated controls (C,D). In some experiments, platelets were pre-treated for one hour with abciximab (0.136 μM), a Fab fragment against α_IIbβ₃, before treatment with agonist. Abciximab-treated platelets showed reduced adhesion to fibrinogen, independent of agonist treatment (B–D). However, the aggregation behavior of platelets was not significantly different for abciximab-treated platelets stimulated with cationic dendrimer (E). The bars in panels C–E represent the mean ± SEM of at least six independent experiments. The (*) indicates significantly (p<0.05) different compared to no treatment. The (**) indicates significantly (p<0.05) different compared to non-abciximab-treated platelets.