Microfabrication and microfluidics for 3D brain-on-chip

Abstract

A revolution in cell culturing has been seen in the last two decades in which 3D culturing became the state-of the-art, with the goal to mimic the in-vivo situation more closely and allow for a physiologically more relevant study compared to the environment in a petri dish. This revolution, however, has not been fully incorporated in the field of in-vitro neuroscience and neither in commercial activities, yet. In this work an attempt has been made to make such a 3D environment available for a conventional planar microelectrode array (MEA) for in-vitro electrophysiology. A reliable platform is realized by combining microfabrication and microfluidics towards a 3D brain-on-chip allowing for drug discovery and the study on diseases. A novel hybrid microbioreactor has been developed as a tool for hydrogel 3D cell culturing on a conventional MEA towards a more physiologically relevant model for the study on brain tissue. The Hydrogel/ poly-dimethylsiloxane (PDMS) bioreactor enables a low shear stress 3D micro-sized culture environment on top of a MEA surface. Furthermore the hybrid bioreactor is explored to realize an on-chip biochemical readout from a 3D culture by a commercial microchip capillary electrophoresis (CE) system with contactless conductivity detection (C4D). An advanced MEA device, termed a microsieve electrode array (μSEA), has been developed by integration of electrode material to a realized highly uniform silicon microfabricated sieving structure. This μSEA allows for the positioning of neurons in 3D pores containing sensing electrodes for extracellular recordings of 3D cultured neurons. Performed characterization of the μSEA includes the tuning of the shape and size of the sensing electrodes, electrical properties and initial studies on neuronal cells. In conclusion, by combining microfabrication and microfluidics a platform has been realized towards a 3D brain-on-chip. The conventional microelectrode array principle is engaged to realize a 3D cell environment for the cells positioned at the sensing electrodes (establishing the neuroelectronic interface) and a microbioreactor add-on is realized allows for 3D culturing of the cells in between the electrodes (neuronal network). Hereby a allowing for more physiological relevant studies with an electrophysiological readout.