Novel polymeric micelles of AB2 type alpha-methoxy-poly(ethylene glycol)-b-Poly(gamma-benzyl-L-glutamate), copolymers as tamoxifen carriers.

A novel AB2 type amphiphilic miktoarm-star copolymer of alpha-methoxy-poly(ethylene glycol)-b-poly(gamma-benzyl-L-glutamate)2 was synthesized by ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxyanhydride. The polymerization was initiated by the terminal amino groups of alpha-methoxy-omega-N,N-bis(aminoethyl) poly(ethylene glycol). Structural properties of the star copolymer were confirmed by IR and 1H NMR spectra. Polymeric micelles were prepared in aqueous solution by dialysis method. Spherical core/shell structure of the micelles was confirmed by transmission electron microscopy and 1H NMR spectra. Dynamic light scattering results indicated that the sizes of the micelles were mostly in the range of 20-50 nm with a narrow size distribution. With the molecular weight of each poly(gamma-benzyl-L-glutamate) block increasing from 2.0 kDa to 13.2 kDa, Tamoxifen loading content increased from 7.34% to 20.30%, corresponding to the increase of Tamoxifen entrapment efficiency from 4.11% to 29.13% and Tamoxifen solubility in water from 11.75 microg/ml to 82.23 microg/ml. In vitro release study of Tamoxifen-loaded micelles at 37 degrees C demonstrated that Tamoxifen-release from micelles at pH 5.0 was much faster than that at pH 7.4. These polymeric micelles are expected to be utilized as promising new drug carriers.