Immobilization Of Biomacromolecules And Cells On Gold Surface And Their Interactions With Other Materials

Physical and chemical methods are widely and increasingly used to study the biomacromolecule interactions and metabolism in living systems. Biomacromolecule interactions are the base of life activities. These reactions may help us to learn more about the basic life phenomenon on the earth. Taking electrochemical method as a principal line covers the total dissertation. And other technologies combined to study biomacromolecule interactions and drug molecule on the influence of cell metabolism.Electrochemical method is a time-honored conventional approach which was already familiar with. But it is still in the prosperous development of the period for studying biological systems. There are many advantages of electrochemistry on this research field, such as no marking requirements for samples and simple preparation, simulating biological reaction process of organism, low damage for sample, high speed of test and high sensitivity, even getting detailed thermodynamic and kinetic information, and so on. Microcalorimetry, fluorescence spectroscopy, UV-vis absorption spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as supporting methods.This work mainly investigated some issues related to biochemistry by means of electrochemical and other measuring methods. These issues included the biological effects of quantum dots at the cellular and molecular levels, the pharmacological and pharmacological properties of some antifungal drugs, the thermodynamics of the adsorption process of DNA on microorganisms which were attached to an electrode and so on. What’s more, we employed the common electrochemical methods to investigate the effects of drugs or toxins on microorganic metabolism.The main experiments and results were shown as follow,(1) In this dissertation, we demonstrated the common methods of self-assembled monolayers (SAMs) on the electrode surface, the effect factors and characterization methods. Considering the research system and conventional approaches to surface adsorption, we strictly controlled the experimental conditions and found the best way to modify the electrode with serum albumin, and the success rate, repeatability and stability of this modified method went up a lot.(2) By using electrochemical method, we studied the interactions of three model microorganisms, Escherichia coli (E. coli), Staphylococcus aureus(S. aureus) and Candida albicans (C. albicans) with DNA. Each microbe was connected to the surface of gold disk electrode by polypeptides, and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The thermodynamic parameters of herring sperm DNA (hsDNA) adsorption on the surface of three microbes were determined by CV. And the equilibrium constant of E. coli-DNA, S. aureus-DNA, C. albicans-DNA is 9.453×105,1.08×106,3.477×106 L·mol-1, respectively. The results shed a new light on DNA adsorption and biological availability of microbe.(3) The inhibition of CdTe QDs on the growth of S. aureus and Halobacterium halobium R1 was investigated by microcalorimetry, electrochemistry, spectroscopy and microscopy methods. The results showed that the living ability and damaged degree were determined by the concentration and properties of QDs. Furthermore,IC50 of CdTe core QDs on the two microbes were calculated and used as a standard for toxicity, and the toxic mechanisms were studied by using spectroscopy, microcalorimetry and ICP-MS. It is concluded that the release of Cd2+ is the main factor for QDs toxicity. Moreover, we compared three different types of QDs, and considered that the toxicity of MPA-QDs is larger than NAC-QDs and the toxicity isn’t consistent with size. The results also demonstrated that microcalorimetry was a practical technique describing growth of microbe, evaluation of medicine efficiency and toxicity. Electrochemistry is an excellent technique for determining toxicity, too.(4) We comprehensively studied the interactions between three MPA-CdTe QDs of different diameters at 2.3,3.1 and 3.5 nm with human serum albumin (HSA). The binding constants of QDs towards HSA, obtained from cyclic voltammetry, electrochemical impedance spectroscopy and fluorescence spectroscopy, were highly coincided with each other. The binding constants were similar for these three QDs with the range of diameter from 2.3 nm to 3.5 nm, but the binding constant of 3.1 nm QDs was always bigger than the others. It may be a reasonable consequence that the appropriate particle size with the surface structure of HSA was matching. This study showed that the particle size of QDs was very important in the interaction between QDs and biomacromolecules. In addition, the controlling step of the QDs-HSA interaction was the diffusion step, approved by the electrochemical experiments.(5) We systematically studied the pharmacology and pharmacodynamics of two antifungal drugs MIZ and ECZ, employing the methods of electrochemistry, microcalorimetry, fluorescence spectroscopy and molecular modeling. We got information about the inhibition for C. albicans and the binding ability towards HSA. The inhibition test indicated both MIZ and ECZ was good potential antifungal drug while MIZ possessed a better capability than ECZ. ECZ showed a better binding strength to HSA than MIZ, because ECZ could bind HSA both in SiteⅠand SiteⅡ, while MIZ could only bind it in SiteⅠ.