Synthesis, Self-assembly, And Hydrogelation Of Dendronlike Poly (ε-L-lysine)-b-PEO Copolymers

Dendronlike poly(?-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 2m primary amine groups) were for the first time synthesized by combining ring-opening polymerization (ROP) of ?-benzyloxycarbonyl-L-lysine N-carboxyanhydride (Z-Lys-NCA) and click chemistry, where Dm-PZLys homopolypeptides were click conjugated with azide-terminated PEO.Then through the deprotection of benzyloxycarbonyl group on the PZLys block, Dm-PLys-b-PEO were achieved.(1) Synthesis and Characterization of Dendron-like/Linear Dm-PZLys-b-PEO Copolymers via ROP and Click Chemistry A new class of dendron-like/linear Dm-PZLys-b-PEO block copolymers was synthesized via controlled ring-opening polymerization (ROP) of Z-Lys-NCA followed by a click conjugation with azide-terminated poly(ethylene oxide) (PEO-N3). Their molecular structures and physical properties were characterized in detail by FT-IR, 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, while that within dendritic copolymers decreased to zero. The secondary conformation of PZLys progressively changed from -sheet to -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 to their blank counterparts. The drug-loaded nanoparticles showed a triphasic drug-release profile at aqueous pH 7.4 or 5.5 and 37℃, and sustained a longer drug-release period for about two months.(2)Synthesis and Hydrogelation of Dendronlike/Linear Dm-PLys-b-PEO Copolymers Dm-PLys-b-PEO copolymers were synthesized through the deprotection of benzyloxycarbonyl group on the PZLys block,their molecular structures and physical properties were characterized in detail by FT-IR, 1H NMR, polarized optical microscopy, and wide angle X-ray diffraction. The self-assembly behavior of Dm-PLys-b-PEO copolymers was investigated by means of dynamic light scattering (DLS), and the corresponding normal and reverse micellar hydrogel from the same polypeptide-based copolymer were prepared via the cooperation of host-guest chemistry and hydrogen-bonding interactions.