Synthesis And Properties Of Hyperbranched Polylysine And Copolymers

Hyperbranched polypeptides that combine excellent physicochemical properties of hyperbranched polymers with good biocompatibility and degradability of polypeptides,have broad potential applications in biomedicine.However,the current synthesis methods of hyperbranched polypeptide materials are limited to thermal polycondensation and iterative ring-opening polymerization of NCA monomers.The few types of monomers,the complicated steps and the unclear mechanism,limit the research on synthesis and application.Basedonthenovelionicmonomer?-tetrafluoroborate-L-lysine-N-carboxy anhydride?NH₃BF₄-Lys NCA?,the reaction conditions of one-pot homopolymerization and copolymerization were investigated,and the homopolymerization mechanism was disclosed.A series of hyperbranched polylysine and its copolymers were prepared,and their self-assembly and drug release properties were discussed.?1?Hyperbranched polylysine was prepared by one-pot method of NH₃BF₄-Lys NCA monomer initiated by triethylamine at low temperature.The branched and secondary structures were characterized and analyzed in detail through ¹H NMR,¹H-¹³C HSQC,GPC,FT-IR and MALDI-TOF-MS.The degree of branching of hyperbranched polylysine is between 0.51 to 0.54,and the secondary conformation of?-turn is mainly formed.The mass spectroscopy analysis and the method of quantum computational chemistry revealed the homopolymerization mechanism.It was found that the cyclic dimer formed at the initial stage of the polymerization initiated the ring-opening polymerization as the secondary initiator.Further,hyperbranched polylysine/gold composite nanoparticles?HPlys@Au NPs?with near-infrared absorption were prepared by using hyperbranched polylysine as stabilizer,which has good photothermal conversion and photothermal stability.?2?A series of different composition ratios of hyperbranched polylysine random copolymers were synthesized by one-pot copolymerization of NH₃BF₄-Lys NCA and Z-Lys-NCA without catalyst/initiator.Structure characterization of copolymers was obtained by ¹H NMR,¹H-¹³C HSQC,GPC and FT-TR.The copolymer composition was consistent with the feed ratio and the degree of branching of the copolymers was 0.15-0.48.The self-assembly behavior of copolymers was studied by DLS,TEM and UV-Vis and copolymer nanoparticles were prepared by dialysis method,with a hydrodynamic size between 88-303 nm.The critical aggregation concentration was measured on the order of 10^-3 mg/mL using the DPH probe,indicating that the nanoparticles have good stability.The drug-loading properties and drug release properties of the copolymer nanoparticles were further tested,indicating that the copolymer nanoparticles can effectively load CPT drug and control the slow drug release.The synthesized polypeptide copolymer nanomaterials were proved to have low cytotoxicity in vitro by MTT method.