Fabrication and characterization of a blood-brain barrier on-a-chip for electrical characterization of cells

Sammanfattning: The blood-brain barrier (BBB) is crucial to maintain brainhomeostasis and prevent toxic substances from entering the brain.Endothelial cells (EC) are essential for the BBB and in this thesistwo different BBB-on-chips were designed for electricalcharacterization of immortalized mouse EC (bEnd3).Indium-Tin-Oxide (ITO) coated glass slides were etched, creating ITOelectrodes with increasing distance between them. The glass slideswere attached to a 3D-printed plastic well with UV-glue. The second prototype was an extension of the first prototype with acopper printed circuit board (PCB) attached to the ITO glass slidesusing silver epoxy to connect the ITO electrodes to the copperelectrodes. The aim with these two chips was to create chips withtransparent electrodes for live imaging of the cells with an opticalmicroscope. The chips were characterized with scanning electron microscopy (SEM) and a profilometer beforeseeding the cells inside the well. The absolute impedance wasmeasured across two parallel electrodes at a time. The impedance wasplotted against the distance between the electrodes. The method usedis called transmission line measurements (TLM) and is used to extractthe sheet impedance between the electrodes to evaluate the barriertightness of the cells. Only one chip from each prototype remained intact after thefabrication and sterilization, making it difficult to drawconclusions from the impedance measurements. However, based on thetwo chips, the TLM for the first prototype followed a linear trendwith a high R-square value whereas, the second prototype showed largevariations, causing the R-square value to decrease