Measuring water toxicity is a lengthy process, and rapid analytical methods are limited. A complementary approach is to measure water toxicity on live cells via electric cell-substrate impedance sensing (ECIS) using a field portable device. This paper presents a study of the longevity of bovine aortic endothelial cell (BAECs VEC Technologies, Rensselaer, NY) by integrating a microfluidic device onto the ECIS sensors. This microfluidic chamber with a network of tree-like perfusion microfluidic channels for cell media delivery to the culturing chamber was fabricated from a biocompatible polymer and tested for longevity studies. This perfusion microchannels were designed as a symmetric arbor with binary splitting to provide equal flow in all the perfusion channels. The microdimensions of the perfusion channels provide high flow resistance, thus carrying low flow rates for a given head pressure and generating low shear stress to the cells during the long-time cell attachment and proliferation period. With such a microfluidic device, cell media can be automatically and evenly perfused into the culturing chamber and no significant shear stress produced by media perfusion was observed. During the longevity study, the BAECs were able to survive in good health for longer than one month. Toxicity tests to study the BAECs responsiveness to health-threatening concentrations of ammonia using the microfluidic ECIS sensor will be also presented. Using impedance spectroscopy technique we demonstrated the BAECs can rapidly respond to ammonia concentrations between the military exposure guideline of 2mM and human lethal concentration of 55mM.
The BAECs monolayer represent the most important component of a biosensor for testing water toxicity in the field. This research concluded that the BAECs could resist at least 34 days on the microfluidic chip and demonstrate high values of cell membrane impedance during long period of time.