MECHANISMS REGULATING BODY DISTRIBUTION OF NANOSPHERES CONDITIONED WITH PLURONIC AND TETRONIC BLOCK-COPOLYMERS

Block co-polymers of poloxamer and poloxamine types have been used to alter the surface characteristics of model nanosphere beads of different sizes. Such modifications, depending on the molecular nature of the block co-polymers, can affect opsonization processes and the overall body distribution of beads following parenteral administration. Certain block co-polymers were able to make nanospheres ''phagocyte resistant'' and to keep them away from Kupffer cells in the liver and, concomitantly, prolong their circulation time in the blood. In other cases, selective bone marrow, spleen and lymph node delivery of beads have been demonstrated. Moreover, a number of poloxamer and poloxamine block co-polymers can enhance the body's defence system both at humoral and cellular levels. The prototype beads described may have implications in radiodiagnostic imaging and organ-specific drug delivery.