Characterization and application of a discrete quartz extended-gate ISFET for the assessment of tumor cell viability

In this work we present a system designed for continuous assessment of tumor cell extracellular pH using a fabricated quartz extended-gate ion-sensitive field effect transistor (EGFET). The extended gate structure was fabricated by patterning gold on a quartz substrate creating a pseudo-reference electrode and sensor below a Si 3 N 4 sensing membrane. Various electrode geometries and configurations were created and each pattern was characterized. A readout/data acquisition system was designed to convert the current output of the EGFET to a voltage that was recorded using a low-power single board computer, which performed a hard "reset" before every data acquisition interval. This setup was able to monitor the viability of SKBR3 mammary gland tumor cells treated with staurosporine. Over a span of 8 hours, the autonomous data acquisition system recorded a steady decrease in cell viability. Results were verified with periodic cell culture images. Future applications include design of an extended gate EGFET array, which allows for accurate monitoring of individual cell cultures.