a b s t r a c tThe toxicity of chromium ions was investigated using mammalian cell cultures on impedance sensors as well as physiological in vitro sensor systems. The performance of commercially available systems like the 2500 Analyzing System (Bionas), xCELLigence (Roche) and Cytosensor Microphysiometer (Molecular Devices) was compared with a novel CMOS-based impedance-to-frequency converter device. Cell-based sensor systems are shown to be powerful tools to detect Cr(VI) pollutions within several hours in the range of multinational drinking water regulations. The ability to distinguish between toxic Cr(VI) and non-toxic Cr(III) species is one advantage of these integral sensor systems. Impedance only devices are not sufficient for the fast detection of toxic chromium species as rapid cellular changes occur only in the respiration system and the cell physiology.

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Abstract. Sensing cellular adhesion via impedance measurements provides a versatile and easily accessible means for monitoring in-vitro cell cultures. Previous works used external electronics connected via cables to microelectrodes to achieve this goal, thus incurring parasitic impedance, electromagnetic interference, and bulky measurement setups. In this work we present a CMOS impedance-to-frequency converter integrated with biocompatible planar surface electrodes to make a compact and robust sensor chip for in-vitro cell monitoring. The system features an 8×8 array of individually addressable electrodes connected to four impedance-to-frequency converter circuits with externally adjustable biasing and square wave output. We present first measurement results obtained with the integrated electronics that demonstrate the successful operation of the system and show good agreement with models of the electrode and cell impedances.