Dendron-like poly(e-benzyloxycarbonyl- L -lysine)/linear PEO block copolymers: Synthesis, physical characterization, self-assembly, and drug-release behavior

摘要

Dendron-like poly(e-benzyloxycarbonyl-L-lysine)/linear poly(ethylene oxide) block copolymers (i.e., Dm-PZLys-b-PEO, m = 0 and 3; Dm are the propargyl focal point poly(amido amine) dendrons having 2 ~m primary amine groups) were for the first time synthesized by combining ring-opening polymerization (ROP) of e-benzyloxycarbonyl-L-lysine N-carboxyanhydride (Z-Lys-NCA) and click chemistry, where Dm-PZLys homopolypeptides were click conjugated with azide-terminated PEO. Their molecular structures and physical properties were characterized in detail by FTIR, ~1H NMR, gel permeation chromatography, differential scanning calorimetry, polarized optical microscopy, and wide angle X-ray diffraction. Both homopolypeptides and copolymers presented a liquid crystalline phase transition for PZLys block, and the transition was irreversible. Moreover, the degree of crystallinity of PEO block within linear copolymers decreased from 96.2% to 20.4% with increasing PZLys composition, whereas that within dendritic copolymers decreased to zero. The secondary conformation of PZLys progressively changed from β-sheet to α-helix with increasing the chain length. These copolymers self-assembled into spherical nanoparticles in aqueous solution, and the anticancer drug doxorubicin-loaded nanoparticles gave a similar morphology compared with their blank counterparts. The drug-loaded nanoparticles showed a triphasic drug-release profile at aqueous pH 7.4 or 5.5 and 37°C and sustained a longer drug-release period for about 2 months.