Synthesis and drug release of star-shaped poly(benzyl L-aspartate)-block-poly(ethylene glycol) copolymers with POSS cores.

Star-shaped amphiphilic block copolymers with polyhedral oligomeric silsesquioxanes (POSS) as cores are synthesized using the "arm-first" strategy. First, the block copolymer poly(benzyl L-aspartate)-block-poly(ethylene glycol) (PBLA-b-PEG) is synthesized via ring-opening polymerization of β-benzyl L-aspartate-N-carboxyanhydride (BLA-NCA) with α-methoxy-ω-aminopoly(ethylene glycol) (mPEG-NH2 ) as a macroinitiator. The copolymers are then immobilized on the eight groups of the polyhedral oligomeric silsesquioxanes (POSS-COOH). The star-shaped copolymers (POSS-g-(PBLA-b-PEG)) are characterized by (1) H NMR and FT-IR spectroscopy and gel permeation chromatography. The star-shaped block copolymers self-assemble into micelles in aqueous medium. Quercetin is used as a model drug and the drug loading content and encapsulation efficiency increases with increasing chain length of the PBLA blocks. The drug release behaviors of drug loaded micelles are investigated and the cytotoxicity assay demonstrates that the POSS-g-(PBLA-b-PEG) copolymers are non-toxic. The star-shaped block copolymers are potential carriers for anticancer drug delivery.