Study On Bioelectrochemistry Of Ferrocene-peptides And Surface Modification Of Magnetic Nanoparticles

The molecule recognitions and the interactions are the bases of life. The researches of the interactions between peptides, small molecules and proteins have wide applications in the field of disease diagnosis, drug reseach and environmental biology. In this paper, a series of ferrocene-peptides were synthesized by combine of bioactive peptides and active electrochemistry, good biocompatibility ferrocene. The structure and the electrochemical properties of the compounds, the interactions between proteins and metals ions were investigated. And Fe3O4 magnetic nanoparticles were synthesized and modified. The main reseach can be summarized as following.In this paper, several ferrocenoyl bioconjugates, such as 1'-cysteaminecarbonyl-1-methoxycarbonyl-ferrocene (yield 30%), 1'-cysteamine carbonyl-1-ferrocenlycarboxylic acid (yield 90%), ferrocenoyl-amino (yield 98%) and glutathione-ferrocen (yield 91%) were synthesized from ferrocene using HBTU and EDC/NHS as coupling agents. The structures of these compounds were characterized by 1H NMR, IR spectra and etc. The gold electrodes were modified by ferrocenoyl-derivatives and mercaptoundecanoic in self-assembly methods. The electrochemical experimental results showed that all ferrocenoyl conjugates were exhibited one electron oxidative reaction.In this work, the glutathione-ferrocens were synthesized. The interactions between glutathione and bovine serum albumin (BSA) were studied by electrochemical method. The results showed that the redox peak potentials of MUA-BSA-GSH-Fc modified electrode were shifted to Epa=0.262 V and Epc=0.159 V from formerly Epa=0.257 V and Epc =0.132 V, respectively.The oxidation and reduction peak potentials of Fc-GSH modified electrode were Epa=0.748 V and Epc=0.645 V, repectively. While, after accumulating Cd2+(20 nmol/L) on the surface of the electrode, the redox peak potentials of Fc-GSH modified electrode were Epa=0.820 V, Epc=0.680 V, respectively. It caused 72 mV anodic shifts compared with the modified electrode with free of Cd2+ accumulation. The oxidation and reduction peak potentials were linear with the concentration of Cd2+. So the CSA-Fc-GSH modified electrode can be employed to detected cadmium ions at low concentration. The experimental results showed that the detection limitation of Cd2+was as low as 0.1 nmol·L-1.Tetrapeptide Gly-Gly-Tyr-Arg and its ferrocene compounds, Boc-HN-Fca-Gly-Gly-Tyr-Arg-OMe (83%) and Boc-HN-Fca-Gly-Gly-Tyr-Arg-OH (80%) were synthesized by HBTU protocol. Cyclic voltammetry (CV) was used to investigate the electrochemical properties of the compounds. The oxidation potential and reduction potential of Boc-HN-Fca-Gly-Gly-Tyr-Arg-OMe were observed at 0.385 V and 0.346 V, respectively. AE was 41 mV. The ratio of Jpa and Jpc was 1.055. While, for Boc-HN-Fca-Gly-Gly-Tyr-Arg-OH, Epa and Epc were observed at 0.532V and 0.453V, respectively. The ratio of Jpa and Jpc was 0.928. The interactions between ferrocenoyl-tetrapeptide and PAP were investigated as well.Magnetic separation is a quick, high efficient, low cost method, and has been used in biological materials for decades. The stabilization and biocompatibility of nanoparticles can be improved after the surface modification. In this work, nanoparticles of Fe3O4 were prepared through an oxygenation hydrothermal method. The chitosan magnetic complexes were prepared by coating chitosan on the surface of Fe3O4 powders through microlatex-crosslinking method. The product was characterized by IR, XRD, TEM, and TG methods. The results showed that the as-prepared powder was 25 nm in size and was of supermagnetism. The content of magnetite in modified nanoparticles was 37.8%. The mechanism for the coating reaction of chitosan to Fe3O4 nanoparticles was also suggested.Furthermore, the Fe3O4 magnetic nanoparticles were modified by coating carboxymethyldextran to yield affinity composite magnetic nanoparticles through chemistry codeposition method. The product was characterized by IR, XRD, TEM, and TG methods. It was found that the modification did not result in the phase change of the magnetic nanoparticles, and the stability of the magnetic nanoparticles in aqueous suspension was improved. Using bovine serum albumin (BSA) as a model protein, the adsorption and desorption behavior of protein on the composite magnetic nanoparticles were studied. The effects, such as protein concentration, temperature, ionic strength and pH value, on the adsorption of MNPs for BSA were investigated. The results showed the adsorption processes were in agreement well with Langmuir adsorption model, and depended on the ionic strength and pH value. The maximum adsorption loading reached 22.37 mg/g at pH 4.7. Compared to the naked magnetic nanoparticles, the adsorption ability of BSA on affinity composite magnetic nanoparticles was enhanced 67% for BSA in low concentration solutions.