Electrochemical impedance spectroscopyElectrochemical impedance spectroscopy is an easy applicable sensitive technique. It is used to get information about the adsorption behaviour and the interactions of biomolecules with the electrode surface in a short measurement duration. Electrochemical processes can be modelled by an equivalent circuit and various parameters reflecting certain properties of the interface can be determined. The electrochemical properties of the interface are influenced by proteins and cells adsorbing at the surface. Different modified surfaces can be analyzed before, during, and after cell contact, respectively. Applying bias potentials also changes the behaviour of attaching cells and proteins. Changes in the medium composition have an influence on the electrochemically detectable surface properties.Biosensors are developed consecutively to detect biomolecules. Enzymes, lipids and membranes can be analyzed and the adsorption behaviour of DNA and antigens at modified electrode surfaces can be determined. Different technologies using microchips were constructed to allow a fast screening of electrochemical properties and discrimination of biological molecules or cells. ApplicationElectrochemical impedance spectroscopy serves not only for determination of the capacity of new battery materials or corrosion behaviour and long term stability of diverse alloys and oxide layers, it can also be used to gain information about biomolecules. The adsorption behaviour of cells [1][2][3] and proteins, [4] the amount of adsorbed proteins, [4][5][6][7] surface charge densities [4][5][6] and adsorption coefficients [5] can be determined. Interactions of implant surfaces with biological devices, changes in the polarizability of functional groups, the transport of ions or dipoles through polymer layers and mineralization processes, for instance of bone tissue can be assessed. The change of the Gibbs free energy and the entropy due to protein binding to the surface can be calculated [4,6,8] and the affinity of biomolecules to the surface can be estimated. [4] Electrochemical techniques are introduced as biosensors. Antigens, ssDNA or enzymes are immobilized at the surface and according antibodies, DNA and distinct proteins can be ADVANCED ENGINEERING MATERIALS 2008, 10, No. 10

Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.