Synthesis and characterization of poly(L-glutamic acid)-block-poly(L-phenylalanine)

Poly(gamma-benzyl-glutamate)-block-poly(L-Phenylalanine) was prepared via the ring opening polymerization of gamma-benzyl L-glutamate N-carboxyanhydride and L-phenylalanine N-carboxyanhydride using n-butylamine center dot HCl as an initiator for the living polymerization. Polymerization was confirmed by H-1-nuclear magnetic resonance spectroscopy and matrix assisted laser desorption ionization time of flight mass spectroscopy. After deprotection, the vesicular nanostructure of poly(L-glutamic acid)-block-poly (L-phenylalanine) particles was examined by transmission electron microscopy and dynamic light scattering. The pH-dependent properties of the nanoparticles were evaluated by means of zeta-potential and transmittance measurements. The results showed that the block copolypeptide could be prepared using simple techniques. Moreover, the easily prepared PGA-PPA block copolypeptide showed pH-dependent properties due to changes in the PGA ionization state as a function of pH; this characteristic could potentially be exploited for drug delivery applications. (C) 2009 Elsevier Ltd. All rights reserved.