Adriamycin release from flower-type polymeric micelle based on star-block copolymer composed of poly(γ-benzyl L-glutamate) as the hydrophobic part and poly(ethylene oxide) as the hydrophilic part

Star-block copolymer based on PBLG as the hydrophobic part and PEO as the hydrophilic one (as abbreviated GEG) was synthesized and characterized. Polymeric micelle was prepared by the diafiltration method. From the measurement of photon correlation spectroscopy, the nanoparticle sizes of GEG-1, GEG-2 and GEG-3 were 106.5 +/- 59.2, 43.8 +/- 0.7 and 13.5 +/- 1.0 nm in number average, respectively, indicating of the formation of polymeric micelle. Also, the nanoparticle sizes were dependent on the PBLG chain length, i.e. the more PBLG content in the copolymer, the larger the particle size. From the observation of transmission electron microscope(TEM), GEG-2 block copolymer had almost spherical shapes with size range about 20-70 nm, that was similar to particle size measurement. Fluorescence spectroscopy measurement indicated that GEG block copolymers associated in water to form polymeric micelles and critical micelle concentration (CMC) values of the block copolymers decreased with increasing PBLG chain length in the block copolymer. Characteristic peaks of the protons of the benzyl group in the PBLG and the methylene protons adjacent to the benzyl group of the PBLG segment in the GEG-2 nanoparticles appeared in 7.2 similar to 7.4 and 5.0 similar to 5.2 ppm, respectively, and disappeared in D2O, indicating the restricted motions of these protons within the micellar core and the very rigid structure of the PBLG core in the GEG polymeric micelles. Release of ADR from the polymeric micelles in vitro was slower in longer PBLG chain length and higher loading contents of ADR. (C) 1999 Elsevier Science B.V. All rights reserved.