Lysine-block-tyrosine block copolypeptides: Self-assembly, cross-linking, and conjugation of targeted ligand for drug encapsulation

This report describes the synthesis and self-assembly of poly(L-lysine)-block-poly(L-tyrosine) (PLL-b-PLT) block copolypeptides. These block copolypeptides self-assembled to form vesicles or micelles with sizes between 100 and 350 nm as confirmed by light scattering and electron microscopy. The spectral properties and chain conformation of these block copolypeptides were studied by UV/vis, fluorescence, and circular dichroism. UV cross-linked micelles and vesicles can be prepared by dimerization of tyrosine residues, evidenced by the presence of fluorescence emission at 410-430 nm. The block copolypeptides can be functionalized by a variety of cell-targeted ligands as demonstrated by conjugation of a saccharide group, lactobionolactone, onto the copolymers. A preliminary evaluation of the glycopeptides for in vitro drug release was studied. Due to the unique features exhibited by both PLL and PLT segments, it can be expected that these amphiphilic block copolypeptides to be useful as targeted drug carriers, functional nanobioreactors, and biomimetic encapsulants in the biomedical fields. (C) 2012 Elsevier Ltd. All rights reserved.