Stable stereocomplex micelles from Y-shaped amphiphilic copolymers MPEG–(scPLA)2: preparation and characteristics

Abstract

Four new Y-shaped miktoarm amphiphilic copolymers were synthesized by ring-opening polymerization (ROP) and click chemistry. The structure of these copolymers was determined by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The stereocomplexes were prepared by an evaporation method and confirmed by FT-IR, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Further the aggregation behaviors of these synthesized polymers and their stereocomplexes were studied by fluorescence spectroscopy (PL), transmission electron microscopy (TEM) and light scattering (LS). Their critical micelle concentrations (CMC) obtained by PL were 0.005 mg mL⁻¹ for MPEG_1.9k–(scPLA_4.5k)₂ and 0.039 mg mL⁻¹ for MPEG_5k–(scPLA_4.5k)₂. The aggregation morphologies of homochiral copolymers were worm-like aggregates, while for the stereocomplexes, the spherical micelles were visually observed. The biocompatibility of these copolymers and their stereocomplexes was evaluated with relatively lower cytotoxicity. Finally, the release of doxorubicin (DOX) encapsulated into the micelles in buffer at pH 5.4 was faster than that at pH 7.4. This study demonstrates that the DOX-loaded stereocomplex micelles could be a potential carrier for cancer treatments.