The Study Of Self-Assembly Of Gemini-like Amphiphilic Peptides And Their Application

Due to good biocompatibility, straight forward chemical modification and inherent molecular recognition, peptides have been very attractive biological building blocks. The designed peptide molecules can self-assemble into well-ordered and specific-shape nano/micro-structures, such as fibers, tubes, tapes, micelles, vesicles and other morphologies, through noncovalent forces including hydrogen bonding, hydrophobic and π-stacking interactions, etc. These prepared functional materials by self-assembly of peptide present a great potential in the biomedical fields of drug delivery, tissue engineering scaffold and biomineralization. Amphiphilic peptides are of special interesting with the advantages of abundant design molecular structures, unique structures of assemblies and special biological functions. On the basis of numerous previously published research works, we designed and synthesized a series of Gemini-like amphiphilic peptides (GAPs) and investigated their self-assembly behaviors and applications in the biomedical field in detail.Chapter1reviewed the recent progress in self-assembly of peptide and their applications, including the molecular structures of peptides, the behavior and mechanism of self-assembly, the structure and property of assemblies and their applications in nanotechnology and biomedical field. Moreover, the developmental direction of peptide self-assembly has been summarized and prospected.Branched protein fibers can be found widely in nature. Some branched fibers are identified to be relative to some diseases and play a particularly significant role in the biological bodies. In Chapter2, a series of GAPs with different length of alkyl tails were designed. Based on these GAPs, branches have been introduced into fibers to form branched fibers. The proper balance of hydrophobic interaction and hydrogen bonding leads to the formation of long branched fibers by (C10-C-O3)2and (C12-C-O3)2. However, due to the damage of the balance,(C14-C-O3)2and (C16-C-O3)2resulted in short nanofibers with nearly no observable branches.Since simple peptides are considered as an important basic building block for prebiotic organization, the spontaneous formation of biologically relevant micro-size vesicles by self-assembly of peptide is vital to the origin of cellular life. In chapter3, a series of GAPs were designed containing two18-carbon-atom alkyl chains with different number of cis double bonds. Using these GAPs, the formation of micro-size cell-like vesicles through the fusion of small ones was demonstrated. It might be due to the change of tightness of arrangement of GAPs in the bilayer membrane caused by the kinked cis double bonds.Constructing artificial highly-ordered aligned arrays of bionanostructures through the self-assembly of peptides is not only critical to the fabrication of advanced functional materials in biomedical fields, but also provides a new insight of understanding of biological self-assembly mechanisms. However, controlling the self-assembly of peptides to form highly-ordered arrays is still one of the challenges in nanotechnology. In chapter4, a series of self-assembled fiberic SAPs as well as corresponding GAPs connected by disulfide bonds were designed. It was found that the long fine fibers could turn to short rod-like fibers by the addition of GAPs into the assembling SAPs systems. Based on these rod-like fibers, parallel fibrous alignments and more sophisticated two-dimensional "knitted" fibrous arrays could be formed. During the formation of such arrays, the "disorder-to-order" transitions are controlled by the temperature-responsible motile short hydrophobic tails of the GAPs with asymmetric molecular conformation. Meanwhile, the resulting long-range-ordered "knitted" fibrous arrays are able to direct mineralization of calcium phosphate to form organic-inorganic composite materials.The interface plays an equally important role in the biological system and constructing highly-ordered aligned peptide arrays on the surface have great theory and application values. In chapter5, based on these GAPs and SAPs designed in chapter4, a simple and mild method to construct highly-ordered and spatial arrays of vertically or horizontally aligned peptide nanostructures such as nanofibers, microfibers and microtubes, has been developed. In addition, the regular structures and their alignments on the surface are controlled by the alkyl chain length of building blocks and the hydrophilicity/hydrophobicity property of surfaces.