Improved understanding of molecular principles of neuronal communication allows new insights into neurodegenerative diseases and possibly to new therapeutic targets. However, there is a lack of tools able to monitor simultaneously electrical and chemicals signals of single cells. Therefore, we propose the development of a novel graphene-enhanced sensor allowing simultaneous monitoring of these two signals with single cell resolution both in cell cultures and organotypic tissue slices. The sensor will be based on surface plasmon resonance imaging (SPRi) and its ability to provide excellent spatial resolution also to electrochemical measurements. More importantly, by integrating graphene both the sensitivity of SPR detection and the current densities of the electrochemical measurement will be enhanced with concomitantly improved biocompatibility. In addition to generating new knowledge about the interplay of electrical and chemical signals of living cells, the development of the anticipated sensors will be an important step towards novel prostheses based on the bidirectional communication with living cells. The core of the sensor will be a ?cell chip? carrying disk microelectrodes, to which cells adhere, surrounded by cell-free ring microelectrodes. Once cells have adhered to the disk microelectrodes, the ring microelectrodes (modified with enzymes or unmodified) are polarized to a potential that allows oxidation or reduction of signaling molecules secreted by the cells. Subsequently, high-resolution SPR images of the ?cell chip? are recorded at high frame rates (~10000 fps) while a physical or chemical stimulus is applied to the cells. SPR images of cell-covered disk microelectrodes are modulated by changes in the extracellular field potential of the cells (which enables us to monitor e.g. the propagation of action potentials). SPR images of the ring microelectrodes will be altered by changes in local current densities invoked by variations in the local concentrations of signaling molecules and will be used to observe chemical signals from the cells. Neuronal cells change their extracellular field potential within the low millivolts range and release only tiny amounts of signaling molecules. Therefore, the sensitivity of SPRi has to be improved in order to be able to record electrical and chemical signals from cells simultaneously. Graphene has already been proved to enhance the sensitivity of both SPR and electrochemical detection. Hence, graphene and its derivatives will be applied for signal amplification. Our optoelectrochemical approach to measure extracellular field potentials with sub-micrometer resolution will excel voltage sensitive dyes and electrically interrogated microelectrode arrays. In addition, it will provide unprecedented spatial resolution and interference elimination to the electrochemical monitoring of chemical signals from cells.

The preservation of the oceans is a major issue of the 21st century. In this context, the European Union is committed to protecting our seas and oceans, as indicated in the Marine Strategy Framework Directive. Despite this, there is today a significant lack of methods aimed at qualifying its environments, and in particular with regard to the impact of pollutants on marine ecosystems. The aim of MOBILTOX project is to contribute to this effort by providing a mobile platform for the in situ assessment of water toxicity as an early-warning system. The platform will combine two analysis complementary modules (biosensors) relying on biological indicators and a sampling drone. The first sensing module is based on whole microbial cells as indicator of overall toxicity (approach based on inhibition of respiratory activity - fluorescent sensors). It will be used to determine the toxicity level caused by the pollutants mixtures in the studied environments (harbours, coastal areas, etc.). This first analysis level will provide information about the overall quality of the environment (the aim is not to detect specific toxic compounds). The choice of the biological indicator is crucial, therefore the cells will be isolated from the targeted environments (coastal area, harbors, mouth of rivers such as the Danube (Romania) or the Loire (France)) in order to ensure a good representativeness of the information collected by this first approach. The second module aims to detect specific groups of contaminants (inhibitors of photosynthesis such as herbicides and metals - main marine pollutants from run-off from agricultural land and industrial activities) via inhibition of photosystem II (PSII) complexes immobilized on electrodes (PSII-inhibition sensor). A preliminary step will be dedicated to identifying of best suitable phototrophic microorganisms owning enzymatic complex likely to be used in this context.