The utilization of pathogen-like cellular trafficking by single chain block copolymer.

Amphiphilic triblock copolymer, poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), Pluronic P85, is unexpectedly shown to utilize sophisticated cellular trafficking mechanisms and enter brain microvessel endothelial cells and primary neurons that are poorly penetrable. Though caveolae serve as a primary entry site for the copolymer single chains, in cells devoid of caveolae, the copolymer can still exploit caveolae- and clathrin-independent routes. This parallels the copolymer's trafficking itinerary with that of biological pathogens. The similarity is reinforced since both bypass early endosomes/lysosomes and transport to the endoplasmic reticulum. The copolymer finally reaches the mitochondrion that serves as its final destination. Notably, it also succeeds to gain entry in brain microvessel endothelial cells through caveolae and in primary neurons through caveolae- and clathrin-independent pathway. In neurons the copolymer accumulates in the cell body followed by anterograde trafficking towards the axons/dendrites. Overall, dissecting the trafficking of a synthetic polymer in multiple cell types triggers development of novel delivery systems that can selectively target intracellular compartments and provide entry in cells currently considered impenetrable. (c) 2009 Elsevier Ltd. All rights reserved.