Revealing cell-substrate adhesion at subcellular resolution with ultra-flat field-effect transistor arrays

In vitro models with isolated cells play an essential role in biological studies, acting as a bridge between complex in vivo research and acellular biomolecular studies. Moving beyond conventional cell-based research methods, which typically require fluorescence labeling of specific biological cues, Electric Cell-substrate Impedance Sensing (ECIS) enables the monitoring of cell adhesion, proliferation, and migration without the need for labels. This work goes beyond the classical ECIS technique utilizing ultra-flat field-effect transistors (UF-FETs) for cell-substrate adhesion experiments at single-cell and even sub-cellular level. Planar surfaces of UF-FETs were achieved by local oxidation of silicon. We monitored the adhesion of cells to the open gates of the UF-FETs using the transistor-transfer function method. This enables non-invasive, real-time monitoring of cells, including cell adhesion, migration and apoptosis- and necrosis-like behavior. To demonstrate single cell resolution, we used fibroblasts from the umbilical cord of rats and induced them to migrate. With our technique we were also able to detect the movement of small lipid vesicles at the gates of UF-FETs demonstrating their ability to monitor the dynamics of soft and fluidic artificial membranes in real-time. Finally, we validated the label-free concept with a less complex and smaller cell model - erythrocyte ghost cells. Our experiments demonstrate that UF-FETs can be used in single-cell tracking and advanced studies for real-time monitoring of artificial membranes on solid surfaces, bridging the gap between biological evaluation and bioelectronic readout.