Biosystem for the culture and electrical characterisation of epithelial cell tissues

The aim of this work was to develop a microchamber system for performing electrophysiological measurements on epithelial surface on culture membranes in the mm2 range. This miniaturised system permits the use of small quantities of epithelial cells, which in relatively short time grow into a tight layer that can be used in electrophysiological (ion transport) experiments. Availability of cells is an issue, for example when the cells originate from human biopsies or from (expensive!) transgenic mice. Apart from having reduced culture surfaces (for use with scarce biological tissues), there are tremendous advantages in having a cell culture mini-chamber. Our systems are with integrated electrical electrodes, micro-fluidic channels and feed-throughs, making them extremely compact and easy to use, thereby avoiding cell perturbation by manipulations. The structures facilitate control of the cell layer growth, the measurement of the cell layer resistance and the transport and diffusion of biological or pharmacological molecules through the cell layer. Moreover we have chosen cheap and easy-to-tool materials for the realisation of disposable devices. We have also fabricated modular devices, in which the cell culture membranes can be reversibly placed within or removed from the system, thereby offering flexibility and economic interest. These microsystems (for biological applications ("biosystems")) are realised using photolithography, various etching procedures (among which powder-blasting), thin film deposition, electrochemical deposition, polydimethylsiloxane (PDMS) moulding and gluing technologies. Both electrical and fluidic characterisation of the biosystems has been performed. Also, a specific study of microelectrode properties of different electrode materials, such as Pt, Ag and Ag/AgCl has been done using various electrochemical experiments and models. The devices are finally tested in real biological experiments. These experiments were carried on with the collaboration of three different biological academic work groups: the group of Prof. W. Hunziker from the Institute of Biochemistry at the University of Lausanne, the group of Prof. Van der Goot from the Department of Biochemistry at the University of Geneva and Prof. J.D. Horisberger from the Institute of Pharmacology and Toxicology at the University of Lausanne. The functionality of our devices has been tested and their potential for the study of transport and diffusion of biological or pharmacological molecules through the cell layer via accurate measurement of (bio-) chemically induced resistance variations, has been demonstrated.