Nanocrystalline diamond-based impedance sensors for real-time monitoring of adipose tissue-derived stem cells.

Cell-based impedance spectroscopy is a promising label-free method for electrical monitoring of cell activity. Here we present a diamond-based impedance sensor with built-in gold interdigitated electrodes (IDT) as a promising platform for simultaneous electrical and optical monitoring of adipose tissue-derived stem cells (ASCs). The impedance spectra were collected in a wide frequency range (from 100 Hz to 50 kHz) for 90 h of cell cultivation in chambers designed for static cultivation. Absolute impedance spectra were analyzed in terms of measured frequencies and cell properties monitored by a high-resolution digital camera. The control commercially-available impedance system, based on gold electrodes exposed to the cultivation media, and also our specially developed sensor with gold electrodes built into a diamond thin film detected three phases of cell growth, namely the phase of cell attachment and spreading, the phase of cell proliferation, and the stationary phase without significant changes in cell number. These results were confirmed by simultaneous live cell imaging. The design of the sensing electrode is discussed, pointing out its enhanced sensitivity for a certain case. The diamond-based sensor appeared to be more sensitive for detecting the cell-substrate interaction in the first phase of cell growth, while the control system was more sensitive in the second phase of cell growth.