Approaches to Increase Particle Blood Circulation Time

Approaches to Increase Particle Blood Circulation Time 

Because of the rapid MPS clearance, site-specific targeting of intravenously administered particulate drug carriers to tissues other than liver and spleen is extremely difficult. To maintain the particles in the bloodstream, one possibility is to block the MPS phagocytic activity prior to particle injection another possibility is to design MPS-avoiding particles. 

The phagocytic potential of the liver and the spleen could be temporarily blocked by using different substances (such as rare-earth metal salts or carbon colloids). For example, injected liposome blood clearance can be reduced after MPS blockade with dextran sulfate or carbon (Souhami et al, 1981). MPS blockade was also achieved by progressively increasing intravenous (i.v.) dosages of liposomes liver saturation was first observed, followed by localization in the spleen and eventually accumulation in the bone marrow (Poste, 1983). 

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