2D gradient formation for on-chip detection of neurotransmitter release using microfluidics

The redox-active nature of certain neurotransmitters released from cells, such as catecholamines, allows investigation of interneuronal communication by means of electrochemical methods. Many diseases of the central nervous system are linked to the malfunction of chemical mechanisms lying behind this communication. Parkinson’s disease, for example, is associated with the dysfunction in the chemical signal transduction of dopaminergic neurons. Most of such diseases develop over large timescales of months to years. As a consequence, long term in vitro studies of days to months are of special interest to find clues for the mechanisms underlying these conditions. State of the art monitoring of neurotransmitter release in vitro, is performed using carbon fiber electrodes. This approach is powerful for single-cell analysis. However, manually positioned individual microelectrodes are difficult to maintain close to the cell for more than several hours. Performing multiple experiments for statistically significant drug screening using this approach is, therefore, very labor intensive and ineffective. We present a novel 64-channel current amplifier capable of simultaneous multichannel recordings at pA level coupled to an on-chip microfluidic system for long-term cell culture under concentration gradients. The system allows development of diversified on-chip cell cultures for days or weeks upon exposure to various growth factors or chemicals with in-line recordings using microelectrode arrays (MEAs). Each MEA contains 64 microelectrodes with 6 µm diameter facilitating parallel screening in a single experiment. We demonstrate on-chip gradient formation and show preliminary results of long term neurotransmitter release recordings with a catecholamine-containing rat pheochromocytoma PC12 cell line