Effect of flow rate and blood cellular elements on the efficiency of red blood cell targeting to collagen-coated surfaces.

The effect of bloodstream factors (flow rate and blood cellular elements) on the behavior of an experimental system simulating drug targeting to injured sites of vessel walls was studied. The system consisted of red blood cells carrying antibody to type I human collagen (drug carrier) and plastic tube with a collagen-coated inner surface (target). The tube was perfused with a 0.5% (v/v) suspension of 51Cr-labeled red blood cells at different linear flow rates and the red blood cell binding to the tube was determined by gamma-counting. It was demonstrated that an increase in the linear flow rate from 0 to 2 cm/s leads at first to increase of red blood cell binding from 2 X 10(5) to 7 X 10(5) cells/cm2 and then to the decrease of binding back to 2 X 10(5) cells/cm2. In the presence of 50% (v/v) of intact red blood cells the binding continuously increases from 2 X 10(5) to 2.5 X 10(6) cells/cm2 without a subsequent drop. On the basis of the obtained results it is concluded that the behavior of the systems for drug targeting in simple in vitro models can drastically differ from the conditions present in vivo.