Water-soluble Modification Of Quantum Dot And Its Application For Labeling PrP

Recently,semiconductor quantum dots(QDs) have been widely applied in biological and medicinal realm as a new kind of novel fluorescent nanomaterials,and have been achieved more and more important results in cell labeling,biomolecular detection and immunoassay.Comparing with traditional organic dyes,QDs possess broad excitation,narrow and symmetric emission, strong resistance to photobleaching and relatively high quantum yields.Nowadays,as a newly arisen interdisciplinary,the research about QDs has become a hot research field in nanomaterials and nanobiomedicine.The main works in this thesis are summarized as follows:(1) Adopting dihydrolipoic acid(DHLA) as modifying reagents,on the basis of strong bidentate interactions between the DHLA ligands and the ZnS surface via their dithiol polar heads, high quality water-soluble QDs was achieved by a slight modification of the procedure of other reports.The influence of fluorescence intensity of DHLA modified QDs by various inorganic metal ions was further researched and the mechanism of the reaction was also discussed.(2) Water-soluble QDs were conjugated covalently to bovine serum albumin(BSA) via 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride(EDC) and N-hydrocylsulfo-succinimide(Sulfo-NHS).The fluorescence intensity was increased after QDs with BSA covalently bound.Because QDs overcome their surface defects when they were covered with BSA,which makes the fluorescence intensity increased significantly.The product(BSA-QDs) had great response to Cu²⁺ which made these bioconjugates having potential to be Cu²⁺ selective probe.High purity of prion protein(PrP^C) was obtained by nickel column chromatography.PrP^C had been labeled via a noncovalent self-assembly process onto surface functionalized QDs and the conjugation was verified by Fluorescence spectra and agarose gel electrophoresis.(3) PrP were found to have a strong photoluminescence at 670nm and the fluorescence intensity of PrP is linearly proportional to its concentration.So a simple,rapid and sensitive detection method for PrP was proposed.The source of photoluminescence was discussed and we speculate that it was caused by fluorescence resonance energy transfer(FRET) between the tryptophan of PrP and hematoporphyrin in the bacteria.