Differences in the molecular weight profile of poloxamer 407 affect its ability to redirect intravenously administered colloids to the bone marrow

Samples of poloxamer 407 obtained from different suppliers have been assessed for their ability to redirect model polystyrene colloids to the bone marrow in rabbits. Only poloxamer 407 obtained from one supplier was found to produce the targeting effect seen previously. The variation in the biodistribution patterns produced by the different samples of poloxamer 407 may by caused by differences in the molecular weight distribution of the polymer.