Construction And Characterization Of Collagen Biomimetic Materials

Collagen represents a large family of 28 different types of extracellular matrix proteins,which display complex structures and diverse functions.Three types of collagen?I,II and III?are the most abundant,accounting for more than 90 % in the total weights of collagens in human body.They display the perfect?Gly-X-Y?n repetitive sequence pattern and distinct triple helix structure,and self-assemble to form fibrous structures.Collagen fibers provide a molecular scaffold for structural integrity and mechanical strength for human body.Collagen,as the major component of extracellular matrix,possesses excellent functional and structural properties,and therefore has received a lot of attention in regenerative medicine and tissue engineering.Therefore,the study of collagen biomimetic materials will contribute significantly not only to understanding the structure and function of collagen,but also to developing novel biofunctional materials such as biomimetic extracellular matrix.This thesis mainly focuses on the design,synthesis and characterization of novel biomimetic materials of collagen.The contents are as follows:Chapter 1: This chapter introduces the structure and important properties of collagen,reviews the progress of peptide self-assembly and briefly discusses the background of biological mineralization.Chapter 2: We aim to construct triple helical peptides to achieve the desired properties of natural collagen.We have for the first time developed a peptide/Ln³⁺ system that the presence of Ln³⁺ ions triggeres the self-assembly of collagen mimic peptides to form well-ordered nanoropes with the characteric periodic banding pattern of natural collagen.Ln³⁺ ions display extraordinary features as photoluminescent materials including long luminescence lifetime,low toxicity,line-like emission,and high photochemical stability,In this system,Ln³⁺ ions not only specifically mediate the reversible self-assembly of collagen mimic peptides,but also offer the biomimetic materials novel luminescent features,which have great potential in cell imaging,medical diagnostics,and luminescent scaffolds for cell cultivation.Chapter 3: We have utilized collagen as biotemplates to synthesize hematite mesocrystals with tunable hierarchical structure.Compared with previously reported proteins,collagen is able to regulate the hierarchical structures of hematite mesocrystals with a much lower concentration,and collagen can produce a richer diversity of hierarchical nanostructures.The distinct?Gly-X-Y?n amino acid sequence pattern and triple helix structure may provide unique capability for collagen in protein-templated biomineralization.Our studies have indicated that the sequential and structural difference of proteins may lead to a plethora of novel nanostructures,which would significantly contribute to the development of improved organic-inorganic hybrid nanomaterials.Chapter 4: We have developed a facile biomineralization method to synthesize enzyme-inorganic hybrid nanomaterials.Under very mild biomineralization conditions,the enzyme mediates the lanthanide ions to form nanospheres.At the same time,the nanospheres provide an ideal support with large surface areas for the attachment of enzymes.Compared with free enzymes,these immobilized enzymes are very active,reusable and more stable.Our studies have demonstrated that biomineralization provides a novel effective mehod to creat enzyme-inorganic hybrid nanomaterials,which have promising applications in biosensors and industrial biocatalysis.