The Development of Biosensors using Integrated Device of Fourier Transform Electrochemical Impedance Spectroscopy (FT-EIS) and Quartz Crystal Microbalance (QCM)

MasterEIS has been widely used as biosensors. But, conventional EIS has some problems. First, the data acquisition takes too much time because it only can acquire one current data at each frequency and the data should be acquired for several periods for signal averaging. Second, as the measurement time gets longer, the electrochemical system changes as well.So, Fourier Transform EIS was developed to solve these problems [4]. The key concept of this novel Fourier transform electrochemical impedance spectroscopic (FTEIS) measurement technique is the application of a Dirac δ function instead of ac wave packets, which is considered to be summation of all the frequency waves of the same amplitude and phase. FT-EIS has been spotted for not only reducing measurement time but also acquiring impedance of various frequencies at real-time. It has been used by studies on biosensors [20], electropolymerization [19], UPDs [21] and so on. In this work, new biosensor platform was developed integrated device of FT-EIS and QCM for the first time investigate surface adsorption or immobilization behavior of biomolecules such as proteins, DNA molecules and other biomaterials that are of fundamental importance in the development of biotechnology and biosensors. QCM is a thickness shear mode (TSM) acoustic wave resonator. As the change of resonance frequency is approximately proportional to the change of mass on the surface of electrode, QCM enables a label-free detection of biorecognition events and is used a different applications, such as monitoring detection of specific antigens, biomolecule binding kinetics, cell adhesion, and DNA detection. FT-EIS allows to measure impedance in-situ, so the integrated device measure simultaneously both the resonance frequency and electrochemical impedance at real time. Two simultaneously obtained data, △f and impedance, can be used to analyze adsorbed viscoelastic mass of biomolecules, density, thickness and electrochemical properties, Rct and Cdl calculated by impedance, on the surface of electrode. According to results of various test In-situ gravimetric and electrochemical responses were simultaneously monitored. The integrated device was capable of distinguishing adsorbed biomolecules at various concentrations. Adsorption of BSA was monitored in-situ and the mass change and electrochemical parameter change can be analyzed in-situ. Using Langmuir adsorption behavior, affinity equilibrium constant was evaluated from each response and similar results were obtained.In the future, the synergy of FT-EIS and QCM can be more pronounced when applied in the system that requires correlation of gravimetric and electrochemical responses