Floating gate ISFET for therapeutic drug screening of breast cancer cells

This paper presents a floating gate Ion Sensitive Field Effect Transistor (ISFET) to monitor the activity of breast cancer cells. We use an ISFET to monitor the change in pH of the cell culture media and to observe the apoptosis of the breast cancer cells when treated with staurosporine. Since ISFETs suffer from inherent mismatch and drift in the threshold voltage, predominantly caused due to accumulation of ions on the surface of the gate, we have integrated a floating gate ISFET to calibrate the device. Floating gate ISFETs have been used to program the threshold voltage of the device either by hot electron injection, Fowler-Nordheim tunneling, and UV to remove charges. In this work we use hot electron injection to precisely program the device and tunneling as a global erase. This enables us to precisely record the changes in pH. These floating gate devices have been fabricated in 0.5 μm CMOS process.