Self-assembly of a hydrophobic polypeptide containing a short hydrophilic middle segment: Vesicles to large compound micelles

This report describes a facile route to prepare the vesicles and large compound micelles (LCMs) from a series of poly(epsilon-benzyloxycarbonyl L-lysine)-block-poly[diethylene glycol bis(3-amino propyl) ether]-block-poly(epsilon-benzyloxycarbonyl L-lySine) (PZLL-DGBE-PZLL) in their water solution, depending on molecular weight of the polypeptides. A pyrene probe is used to demonstrate the aggregate formation of PZLL-DGBE-PZLL in solution, and also to measure their critical micelle concentration as a function of molecular weight of the polymer. Transmission electron microscopy, atomic force microscopy, dynamic light scattering and confocal laser scanning microscopy are used to observe their aggregate morphologies. Rhodamine B is used as a fluorescent probe to confirm the structure of large compound micelles composed of many reverse micelles with aqueous cores. These polypeptides are prepared by ring-opening polymerization of a-amino acid N-carboxyanhydrides with a small molecule as the initiator. Their structures are confirmed by NMR and SEC-MALLS. These vesicles and large compound micelles are extremely expected to be used in drug delivery.