Study on the Synthesis and Biomedical Applications of Peptide-Gold Composite Nanostructures

Author:Yuan Ming

Supervisor:zhang feng


Degree Year:2019





Gold nanostructures have unique physical and chemical properties and good biocompatibility.In recent years,gold nanostructures have been widely applied to different scientific fields such as chemistry,materials,and other interdisciplinary fields like nanobiomedicine.The properties of gold nanostructures depend not only on their structural size and mophology,but also on their surface ligands.In recent years,due to the self-assembly characteristics of some biomolecules and the tunability of their structures and functions,the synthesis and applications of novel(multi-)functional biomolecule-gold composite nanostructures become a researching hotspot.However,the molecular mechanism for the synthesis is rarely reported in a systematic way.Considering of the capacities of self-assembling,reducing and bio-recognition,this thesis selects self-assembling peptides as a typical kind of biomacromolecules,by using different spectroscopies,and in combination with high-resolution electron microscopy,liquid phase in situ atomic force microscopy,X-ray diffraction and photoelectron spectroscopy,and systematically studies the mechanism of self-assembling peptide molecules in the synthesis of gold nanostructures.In addition,we have also experimentally demonstrated the potential applications of peptide-gold composite nanostructures in the biomedical field.The main researching contents and results of this thesis are listed as followings:First,through sequence designing,we have constructed a series of multifunctional self-assembling peptides,and by using them as protecting agents,we have developed a new approach to rapidly synthesizing peptide-gold composite nanostructure under ultraviolet irradiation conditions.In addition,we have also elucidated that how peptide molecules modulate both the shape and size of the gold nanostructures.Second,during studying on a self-assembling peptide with two structural domains,GAV-FF,we found a potential method to construct multifunctional or multimode self-assembling peptides via directly covalent crosslinking of different structural/functional domains.It is worth noting that GAV-FF cannot only execute the reduction function,but also maintains the self-assembling modes for each structural domains,that are hierarchical fibrillization in aqueous solutions and template-assisted epitaxial growth of nanofilaments on the surface of mica.Third,through parallel screening experiments,we have successfully screened out a number of peptide molecules that can synthesize blue and red fluorescent gold nanoclusters,and elucidated the molecular mechanism that how the peptide sequence and the position of some important amino acids modulate the morphology and properties of gold nanoclusters.Besides,this thesis also reports the phenomenon that some peptide sequences can self-assemble to blue fluorescent nanostructures,and the possible mechanism is also discussed.Finally,this thesis also demonstrates the potential applications of the as prepared peptide-gold nanoclusters in the biomedical field.For example,red fluorescent peptide-gold nanoclusters can be developed to not only temperature sensitive sensors,but also the heavy metal Hg(II)ion probes(with a detection limit of 25 nM).And due to the excellent biocompatibility and targeted biorecognition capacity,this thesis has also successfully verified the feasibility for applying the fluorescent peptide-gold nanoclusters to both biolabeling and bioimaging.