Polypeptoid-block-polypeptide copolymers: synthesis, characterization, and application of amphiphilic block...

We report the synthesis of polysarcosine-block-polyglutamic acid benzylester (PSar-block-PGlu(OBn)) and polysarcosine-block-polylysine-ε-N-benzyloxycarbonyl (PSar-block-PLys(Z)) copolymers. The novel polypeptoid-block-polypeptide copolymers (Copolypept(o)ides) have been synthesized by ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs). Polymerization conditions were optimized regarding protecting groups, block sequence and length. While the degree of polymerization of the PSar block length was set to be around 200 or 400, PGlu(OBn) and PLys(Z) block lengths were varied between 20 to 75. The obtained block copolymers had a total degree of polymerization of 220-475 and dispersity indices between 1.1 and 1.2. Having ensured a nontoxic behavior up to a concentration of 3 mg/mL in HEK293 cells, the novel block copolymers have been applied to the synthesis of organic colloids (by miniemulsion polymerization and miniemulsion solvent evaporation process). Colloids of around 100 nm (miniemulsion polymerization) to 200 nm (miniemulsion process) have been prepared. Additionally, PSar-block-PGlu(OBn) copolymers have been used in a drug formulation of an adenylate cyclase inhibitor. Micelles of 28.0 nm (without drug) and 33.0 nm (with drug) diameter have been observed by fluorescence correlation spectroscopy (FCS). The polypeptoid-block-polypeptide formulation increased solubility of the drug and enhances its bioavailability, which leads to a reduction of intracellular cAMP levels in MaMel 91 melanoma cells.