Fabrication Of Biomolecule Encapsulated Metal Nanoclusters And Their Applications In Bioimaging And Biosensing

With the continuous improvement of the economy and living standards of human beling in the world,major issues such as environmental pollution and life and health have drawn increasing interests as hot spots.Nanobiotechnology involves nanoscience,biotechnology,biochemistry and medicine is an emerging field of research.With the advancement of nanomaterial technology,the integrated strategy of selecting highly active biomolecules and various metal nanoparticles have unparalleled opportunities in photonic,electronic,catalytic and biological properties,thus bringing great potentials for various applications in the association with interdisciplinary.Recent studies have shown that a variety of biomolecules(peptide,protein and DNA)can be successfully applied to the synthesis of various metal nanoclusters due to their special sequence and conformation,and further participate in the precise control of the size and composition of luminescent metal nanoclusters.It is worth noting that relatively mild synthetic conditions will greatly contribute to biological activity and the regulation of complex conformational retention of biological templates.The combination of various types of metal nanoclusters and different types of biological templates unprecedentedly create a large number of nano-molecules with combined functions and synergistic effects,opening up new possibilities in biomedical fields.Metal nanoclusters(such as Au,Ag,Cu,Pt,Pd,and Cd et al.)consisting of roughly several to dozens of metal atoms,are emerging class of fluorescent imaging materials.The limited number of metal clusters have ultra-fine sizes of less than 2 nm and bridge the"missing link" between atoms and metal nanoparticles.Their physicochemical properties are controlled by their sub-nanometer sizes.Compared to the continuous energy levels of the metal nanoparticles,the discrete energy levels of the metal nanoclusters allow the electronic transitions between energy levels by interaction with light,and result in the observation of significantly different optical,chemical,and electrical properties.The physicochemical properties of metal nanoclusters are strongly influenced by the type,size and structure of metals.Compared with quantum dots,organic fluorophores and fluorescent proteins,metal nanoclusters have a series of outstanding features,including improved optical properties,excellent biocompatibility,ease of equipment and high biological activity.Therefore,fluorescent metal nanoclusters can also be widely used as a new competitive bioprobe in the field of biomedical applications.In current study,our goal is to explore bioactive peptides as biomolecular templates for the synthesis of various metal nanoclusters as functional fluorescent imaging materials,which can be used for various biomedical applications of materials such as biosensing,bioimaging,drug delivery,biocatalysis,cytotoxicity and various therapeutic applications.The current contents of the study are mainly as follows:(1)Water-soluble fluorescent Au NCs were prepared via a one-step green method by using aprotinin as a biomolecular template for the first time.The synthesis mechanism of Au nanoclusters was analyzed.Through a series of characterizations,the microscopic morphology,optical properties,chemical composition,surface element composition and valence were systematically studied.Based on the synthesis of fluorescent materials,the use of the fluorescent gold nanoclusters solution for the first time was successfully applied to the detection of heavy metals Hg2+,Cu2+ and trypsin,and exhibits excellent detection performance with high selectivity and high sensitivity.In addition,the prepared Au nanoclusters were successfully applied to staining and imaging of Hela cell and their intracellular distribution and sublocalization were observed.Ap-Au NCs enter the cytoplasm through the HeLa cell membrane.After incubation for 24 h,Ap-Au NCs enter the nucleus and target to the nucleus.(2)The as-prepared ?-globulin encapsulated fluorescent Au nanoclusters can be effectively used for the detection of metal ion such as Hg2+,Cu2+ and Mn2+.Fluorescence intensity changes enable visually colorimetric sensing.Meanwhile,the ?-globulin encapsulated gold nanoclusters showed significant fluorescence degradation in the presence of papain,penicillamine and cysteine,indicating great possibility for fluorescence based detection.(3)The silk fibroin-derived polypeptide was used as a biomolecular template for the synthesis of water-soluble fluorescent Ag nanoclusters for the first time.The formation mechanism of Ag nanoclusters was analyzed.Through a series of characterizations,the microscopic morphology,optical properties,chemical composition,surface element composition and valence of the samples were systematically studied.Furthermore,the results of cell imaging and biocompatibility from nitrogen-doped carbon quantum dot was presented and the corresponding results was compared with Ag nanoclusters.Herein,gold nanoclusters and silver nanoclusters were prepared from peptide or protein to obtain composite functional fluorescent imaging materials.The strategy of integrating biomolecule with various metal nanoclusters effectively combine the characteristic physicochemical properties,optical,electronic and catalytic properties and biological functions of biomolecules,and are widely used in environmental detection and protease detection and cell imaging as well.In the view of innovative integrated system and design strategies,current results bring new ideas for the development of bioinspired metal nanoclusters in the field of biomedical applications.