Biomaterial Interface Investigated by Electrochemical Impedance Spectroscopy

Abstract

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

Corrosion Behavior Analysis of Plasma-assited PVD Coated Ti-6Al-4V alloy in 2 M NaOH Solution

“…TiO 2 is formed spontaneously on the surface of Ti-6Al-4V alloy when immersed in NaOH according to the following anodic reaction 11,13 : the amplitude of the oscillating current, ω is the angular frequency of disturbance and ϕ is the phase angle 19 . Electrochemical impedance spectroscopy reflects the dielectric behavior, the oxi-reduction reactions and the mass transfer in the electrochemical interface (EI).…”

“…The EI's capacitive response usually comes from a non-ideal capacitor. Thus, a constant phase element (CPE) replaces pure capacitance according to Equation 3 [18][19][20] . and temperature of such solutions are decisive for this reaction occurs.…”

“…This measurement is done via a sine disturbance in potential and is read as lagged current in a characteristic phase angle. The Equations 1 and 2 correspond to the disturbance in potential and to the response in current 18,19 .…”

Quantum dot-based microfluidic biosensor for cancer detection

“…Prior to application of the QCdSe based chip for the biosensing, its electrochemical behaviour is experimentally characterized through EIS using 5 mM K 3 properties in response to a small AC signal as a function of frequency. 19,20 Microfluidic devices use low sample volumes and provide fast reaction rates due to the smaller diffusion distances, and a diffusion restriction model can be applied. 9 The bioelectrical model includes both energy storage and dissipation elements and is shown in Figure S2.…”

“…In the Nyquist plot of the impedance spectra, a usual semicircle is observed which corresponds to the electron transfer resistance process (R ct ) and the magnitude of R ct depends on the dielectric and insulating features that can be used to interpret electrodeelectrolyte interface properties. 20 The modification over the chip surface causes a change in its R ct value and in case of a DNA biosensor, the change in R ct value may be induced by hybridization or the conformational changes of DNA to an electrical signal. 12 The modification of QCdSe-LB/ITO electrode with DNA probe, results in an increased R ct value of chip from 6.7 kX (curve i) to 53.8 kX (curve ii).…”