Nonionic Block Copolypeptide Micelles Containing a Hydrophobic racemic-Leucine Core.

Block copolymer micelles have been used extensively as carriers for therapeutic drugs and diagnostic molecules. Here, we report the synthesis of nonionic, block copolypeptides, K(P) (x)(rac-L)(y), which have a "reversed" rod-coil structure composed of a hydrophilic, rod-like, α-helical segment attached to a disordered, racemic hydrophobic segment. The self assembly of these block copolypeptides in water was studied, and their compositions were optimized to identify a sample, K(P) (100)(rac-L)(10), which is able to form well defined micelles that are very stable against dilution, high temperatures, and various media. Micelle structure was determined using a combination of electron microscopy and dynamic light scattering measurements. The potential of these micelles as drug delivery carriers was evaluated by encapsulation of the anticancer drug camptothecin. The drug containing micelles were found to be stable.