Preparation And Seif-assembly Of Hyperbranched Polymer Peptide/Protein Hybrid Materials

Hyperbranched polymers possess a highly branched structure and many properties that linear polymers do not have,such as high solubility,low viscosity,and high levels of terminal functional groups,and can be applied to drug delivery systems,gene carriers,and nanomaterials and other fields.The preparation of hyperbranched polymers by photoinduced metal-free atom transfer radical polymerization（ATRP）can not only offer hyperbranched polymers with controllable structure,but also avoid the residual metal catalysts in the hyperbranched polymers,which will affect their application in the biological field.Through the choice of a suitable construction method,the protein/polypeptide can be modified onto the star polymer with the hyperbranched polymer as the core to obtain the polymer protein/polypeptide conjugate.The hybrid material has both the special properties of hyperbranched polymers and the biological functions of protein/polypeptide,which can be effectively used in the field of biomedicine.This paper mainly discusses the preparation of thermoresponsive hyperbranched polymers and the construction as well as self-assembly of star-shaped polymer-protein/polypeptide hybrid materials with hyperbranched polymers as the core.The specific research contents are as follows:（1）The monomer initiator 2-（2-bromoiso-butyloxy）ethyl methacrylate（BMA）was firstly obtained through esterification reaction,and then the thermoresponsive monomer polyethylene glycol methyl ether methacrylate（DEGMA,M_n=188）,was selected to copolymerize with it.A series of hyperbranched polymer h PDEGMA with different branching degree（DB）and molecular weight were prepared by photoinduced metal-free ATRP.With h PDEGMA taken as a macroinitiator to polymerize dithiopicolinyl methacrylate（DSMA）monomer,star polymer h PDEGMA-star-PDSMA was obtained.Finally,the peptides were modified into the star polymer by conducting the exchange reactions between the dithiopyridine group on the star polymer and the glutathione and HAIYPRH（T7）polypeptides with sulfhydryl groups respectively,and two star-shaped bioconjugates h PDEGMA-star-PGS and h₁PDEGMA-star-PT7 modified with polypeptides were obtained.The thermoresponsiveness and self-assembling behavior of these two bioconjugates were researched.The two bioconjugates can self-assemble into vesicles above the lower critical solution temperature（LCST）.In cell experiments,the assembly formed by h₁PDEGMA-star-PT7 has low toxicity to L929 and MCF-7 cells and can be successfully taken up by MCF-7 cells.（2）Through photoinduced metal-free ATRP,the thermoresponsive monomers polyethylene glycol methyl ether methacrylate（DEGMA,M_n=188）and polyethylene glycol methyl ether methacrylate（OEGMA,M_n=300）were selected as the comonomer to copolymerize with the monomer initiator BMA in the research content（1）,and a series of hyperbranched polymers h P1 with different branching degrees and molecular weights were obtained.With h P1 taken as a macroinitiator to further polymerize a segment of DSMA monomer,star polymer h P2 was obtained.The lysine residue of lysozyme was then reacted with a sulfhydryl group by diiminothiolane hydrochloride（Traut’s reagent）,and the lysozyme was conjugated into the star polymer by conducting a thiol disulfide bond exchange reaction to obtain the polymer-lysozyme bioconjugate h P3.The thermoresponsiveness and the size and morphology of polymer-lysozyme conjugates above LCST were investigated,and the catalytic activity of lysozyme on conjugates was studied.It was proved that the biological activity of lysozyme on conjugates basically remains unchanged.