Synthesis And Properties Of Multi-armed Polyglutamate-based Materials

Owing to both the adjustable macromolecular structure (i.e., architecture and conformations) and biocompatibility, biomimetic poly(amino acid)-based materials received much attention in the field of polymeric biomaterials and biotechnology. Multi-armed poly(amidoamine)-poly(benzyl L-glutamate) amphiphiles (PAMAM-PBLG) were synthesized by the ring-opening polymerization (ROP) ofβ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) using primary amine-terminated PAMAM dendrimer as the macroinitiator. Both 1H NMR and 13C NMR demonstrated that all the primary amine of PAMAM participated in initiating the ROP of BLG-NCA monomer, and the chain length of PBLG can be adjusted linearly by the molar ratio of BLG-NCA monomer to PAMAM. Moreover, these multi-armed PAMAM-PBLG amphiphiles exhibited bothα-helix andβ-sheet conformations similar to linear analogues, while their multi-armed architecture could enhance secondary conformations content of PBLG segments. Meanwhile, the PAMAM-PBLG amphiphiles presented weaker liquid crystalline textures than linear analogues, and their multi-armed architecture to some extent improved the thermal stability of PBLG. Furthermore, spherical nanoparticles could be generated by direct injection of these PAMAM-PBLG solutions into distilled water, and their average size (38 - 275 nm) could be adjusted through the multi-armed architecture, the PBLG composition, and the concentration of these amphiphiles. These nanoparticles were stable in aqueous solution within 64 days at room temperature.Dendritic poly(amidoamine)-b-poly(L-glutamate) (PAMAM-PLG) biohybrid was synthesized by the ring-opening polymerization ofβ-benzyl-L-glutamate N-carboxyanhydride monomer, followed by the deprotection of benzyl groups on poly(benzyl-L-glutamate). The self-assembly behavior of the PAMAM-PLG biohybrid was investigated by means of UV-vis, dynamic light scattering (DLS), and transmission electronic microscopy (TEM). UV-vis analysis demonstrated that the critical aggregation concentration of PAMAM-PLG was dependent on the pH value of aqueous solution. DLS results further confirmed that the average size of the self-assembled nanoparticles decreased gradually with the increasing pH value of the PAMAM-PLG solution. These results evidenced that the PAMAM-PLG biohybrid had a pH-sensitive self-assembly behavior in aqueous solution.