BLOCK-COPOLYMER MICELLES AS LONG-CIRCULATING DRUG VEHICLES

The development of block copolymer micelles as long-circulating drug vehicles is described. As well, a recent fundamental study of block copolymer micelles, where much insight into their structures and properties has been realized, is briefly summarized in order to shed light on their properties in vivo. There is emphasis on block copolymer micelles having poly(ethylene oxide) as the hydrophilic block and poly(L-amino acid) as the hydrophobic block, with some discussion on the properties of poly(ethylene oxide). Comparisons are drawn with other drug vehicles and with micelles formed from low molecular weight surfactants. Micelle-forming, block copolymer-drug conjugates are described. Hydrophobic drugs, such as doxorubicin, distribute into block copolymer micelles, and details of several examples are given. Finally, the paper presents studies that evidence the long circulation times of block copolymer micelles. Like long-circulating liposomes, block copolymers that form micelles accumulate passively at solid tumors and thus have great potential for anti-cancer drug delivery.