The Synthesis And Properties Of Biomaterials-fluorescent Noble Metal Nanoclusters

Due to the properties of low toxicity, optical stability, water solubility, goodbiocompatibility and strong photoluminescence, noble metal nanoclusters havebecome potential candidates of quantum dots. With the discovery of novelfluorescent nanomaterials, protein stabilized-metal nanoclusters andoligonucleotide stabilized-metal nanoclusters have helped to promote theapplication of nanomaterials in biomedical imaging and molecular detection. Inthis paper, by investigating the influence factors of bovine serum albumin (BSA) as atemplate for synthesis of gold nanoparticles cluster (AuNCs), we developed a new andrapid method of BSA-AuNCs preparation. Furthermore, we analyzed its fluorescenceperformance and tried to use it in thiourea testing and cell imaging. Fluorescentsilver nanoclusters (DNA-AgNCs) were synthesized with DNA as template whichcould be applicated in tumor cell targeted imaging. The concrete research contentswere as follows:1. We studied the influence of the mass concentration of BSA, the dosage ofreducing agent ascorbic acid (AA), pH and temperature on the synthesis ofBSA-AuNCs. Results showed that under the condition of60℃, adding reducingagent AA, adjusting pH to12and reacting about1h, BSA-AuNCs with highfluorescence intensity could be synthesized. We put forward a fast, economicalmethod for preparation of BSA-AuNCs emitting red fluorescence whose excitationwavelength was488nm and emission wavelength was624nm.2. The properties of the BSA-AuNCs which was prepared under the optimizedconditions was investigated, we found that BSA-AuNCs was stable in a highconcentration of salt (NaCl), the same buffer with different pH and the differentbuffer with the same concentration and pH. The solution of BSA-AuNCs could also bestored for a long time. The results of zeta potential, fourier infrared spectrum (FTIR)and circular dichroism (CD) demonstrated that the stability of BSA-AuNCssynthesized under60℃was similar to the classical materials prepared at40℃andthe effects on the protein conformation were almost the same, the BSA secondarystructures turned from complicated conformation to disordered structure and theaffect of NaOH on BSA conformation was irreversible. The fluorescence of the asprepared BSA-AuNCs was quenched in the presence of thiourea and had a good linearin a certain range, thus we proposed a new method of detection thiourea based onfluorescence. BSA-AuNCs could also be used to cell imaging. 3. We designed a DNA chain which could recognize epithelial tumor cellsspecificly and in situ synthesis of DNA-AgNCs. The excitation wavelength of the asprepared DNA-AgNCs was565nm and emission wavelength was616nm. Under theoptimum temperature30℃, the fluorescence intensity of DNA-AgNCs was higherwhich might be associated with the conformation of DNA and DNA-AgNCs had aexcellent fluorescent stability. We established an experimental basis for epithelialtumor cells MCF-7imaging.