Self-Assembly And Biomimetic Mineralization Behaviors Of Polypeptides Based On Poly(L-lysine)

Polypeptides have good biocompatibility,and their assemblies have often used in research in the field of biomedicine.Polypeptide vesicles are one of them.However,the existing polypeptide vesicles are usually assembled by block copolymers.No one has reported the study of homo-polypeptide vesicles,and its formation mechanism needs to be filled.In addition,polypeptides can be used as templates for biomimetic mineralization to combine with inorganic ions to form composite materials.It also has potential application value in the field of biomedicine.However,existing research templates are mainly concentrated on polypeptides containing negative ions,and there is very little about research on polypeptides containing positive ions or both positive and negative ions.Based on this,we designed and synthesized homo-polypeptides with both hydrophilic and hydrophobic components,self-assembled to form vesicles by solution self-assembly method,and its formation mechanism was characterized and analyzed in detail;secondly,polypeptides containing positive ions and both positive and negative ions were prepared and used as templates for the biomimetic mineralization of calcium carbonate and barium carbonate.The main research contents and conclusions are summarized as follows:(1)Homo poly(N?-carbobenzoxy-L-lysine)(PZlys)possessing hydrophobic and hydrophilic groups was synthesized and can self-assemble to vesicles in THF/H₂O solutions.The combination of CD,FT-IR and LF-NMR measurements distinguished the hydrophilic and hydrophobic components in PZlys and proposed the self-assembly mechanism of vesicles induced by hydrogen bonding of side-chain.Furthermore,Poly(?-benzyl-L-glutamate-co-N?-carbobenzoxy-L-lysine)[P(BLG-co-Zlys)],with different lysine components was synthesized.Due to the introduction of the hydrophobic glutamic acid component,the proportion of hydrophilic side-chain is reduced,making the co-polypeptide less hydrophilic,and can only self-assemble to micelles,thus further verifying the mechanism proposed above.(2)The homo-polypeptide PLL with positive ions and the co-polypeptide PLGA-co-PLL with both positive and negative ions were synthesized.Using them as templates for biomimetic mineralization,by changing the mineralization conditions,various morphologies of Ca CO₃/Ba CO₃ crystals were obtained.Their mineralization mechanisms were explored.When polypeptide is used as a template molecule,its molecular chain exhibits a typical?-helical conformation in solution under certain p H conditions.Ca²⁺were adsorbed to it,combined with CO₃^2-to form Ca CO₃nanocrystals,and they gather around the template molecular chain to form crystal nuclei,which grow in all directions to form the final crystals.The mineralization mechanism of Ba CO₃ crystals is similar.