The Synthesis Of Gold Nanoparticles And Applications In Biology

Gold nanoparticles (Au-NPs) have stimulated tremendous research interest owing to their fascinating optical, electronic, biological compatibility, and promising applications in catalysis, detection, biological sensing, ducg carrier, biological probe and gene chip etc in the21st century. There are many synthetic methods to prepare Au-Nps, but most of the methods of synthesis are more complicated purifying process and the Au-NPs unstable in a wide range of PH value and a larger concentration of salt, which limit their application in biological system. For Au-NPs used for biological application, most researchs are not relatively comprehensive. Thus, we present a new, simple, green method to control synthesis of Au-Nps in our study. It can stable in a wide range of PH value and a larger concentration of salt. We faund a system to research three kinds of different surface charge of Au-Nps, which interact with DNA, BSA and e. coli.(1)The synthesis of Citrate (CA) and Cysteine (Cys) capped gold nanoparticles (CA-Cys@Au) used citric acid sodium, cysteine and hydrogen tetrachloroaurate tetrahydrate with vibrating in room temperature. This was a new, simple, green mothed of synthesis of gold nanoparticles. The best ratio was that Mcys:MHAuC14: MCA=0.5:1:3.88. We researched the stability of CA-Cys@Au and the interaction with BSA, and gave a mechanism of the reaction. We found it could stable in solution, which was PH=4to13and C(NaCl)=0to0.04M, which would not form aggregation. There had a good liner relationship with A700/A525at C(NaCl)=0to0.06M that could be used to analysis the ionic strength in the solution. The mechanism of this reaction may be that, first, Citrate-reduced AuCl4-to Au, second, Cysteine connect Au with-SH, which capped Au as core(Cys@Au), the last, the excess of Citrate-joined Cys@Au with the residue of cysteine as outer(CA-Cys@Au).(2) The quenching mechanism between BSA with CA-Cys@Au was the static quenching, CA-Cys@Au with BSA formed a baes complexes. We could know that the binding sites (n) were1and binding constant (kb) was107M-1from Au-Nps intecating with BSA at different temperature. The more C(Nal), the letter baes complexes would be formed. Thermodynamic analysis to know that hydrogen bonds and Van der Waals interactions played a important role in the binding reaction between them. Besides, Electrostatic forces and BSA’s space structure had a certain extent form analysising different concentration of salt. (3) We synthesis three different about20nm Au-Nps with charge of surface (Citrate@Au, PEG2000@Au, CTAB@Au). The best unite was Citrate@Au combined with DNA from them responsing with DNA. So we used Citrate as modifier to obtain Citrate@Au, the next DNA replaced Citrate to get DNA@Au. It had specific detection to Hg2+, which had a high sensitivity and low cost. It could applicable in our life. Fluorescence spectrum analysis to know, in the BSA isoelectric point BSA was the best role with the surface of negative Au-NPs, but in the choice of applied biological research, the positive charge is better, because it had well stability in a certain PH change range and the combination of BSA is very stable. Forming the cell membrane surface of the different electric charges interacted with the cells endocytosis and exocytosis; we knew that the positive charge’s Au-NPs were the easier to come in the E. coli. The absorptive amount compared with negative charge of neutral was about8-10times. It had some significance to the Au-NPs as drug carrier for directional receptors.