Hydrogen Bonding Interaction Induced Complexation of mPEG-b-PAA and Star PDMAEMA-b-poly (HEMA-g-PCL) Hybrid Micelles in Water

Abstract

A series of amphiphilic star-shaped copolymer, poly(dimethylaminomethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate -graft- poly(ϵ-caplactone)), s(PDMAEMA-b-P(HEMA-g-PCL))4, were synthesized by atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP) with PDMAEMA as hydrophilic star core and PCL as hydrophobic outer arms. The star copolymer micelles were formed in different pH values and the hybrid micelles were obtained from s(PDMAEMA-b-P(HEMA-g-PCL))4 and methoxy-poly(ethylene glycol)-block-polyacrylic acid (mPEG-b-PAA)by hydrogen bonding interaction between PDMAEMA and PAA. These copolymers were characterized by 1H-NMR spectroscopy and size exclusive chromatography(SEC). pH sensitive self-assembly behavior of these copolymers could be observed by increasing pH values, which was examined by fluorescence spectra, dynamic light scattering (DLS), zeta potential and transmission electron microscopy (TEM). As a result, these copolymers could form micelles with diameters under 500 nm from pH 2.0 to 8.0 but nanoparticles above pH 9.0. MTT assay exhibited that the addition of mPEG-b-PAA could increase the cell viability from 40% to 90%. The drug release assays of indometacin (IND) drug loaded star copolymer micelles and hybrid micelles were investigated in Phosphate Buffered Saline (pH 7.4) at 37°C. mPEG-b-PAA had less influence on the drug release and the cumulative releases of all the micelles were from 57.5% to 69.7% after 40 h.