The study of a cell-based TSM piezoelectric sensor

Piezoelectric biosensors incorporating living cells are capable of delivering functional information in contrast to protein-based sensors, which provide analytical data. Functional information, i.e. information about the physiological effect of an analyte or measurand on a living system, is often desired in many important applications in pharmacology, toxicology, cell biology and environmental measurements, including the applications in the area of bioterrorism and biowarfare. Preliminary results describing the properties of a thickness shear mode (TSM) acoustic sensor operating under different ambient conditions with immobilized endothelial cells are presented. A TSM acoustic sensor, which utilizes shear motion generated by a vibrating AT-cut quartz resonator, has the ability to monitor interfacial phenomena at the sensor/liquid interface. The cells were placed in Dulbecco´s modified Eagles media (DMEM) solution, which provided appropriate conditions for maintaining cells at the required level of bioactivity. Initially, the sensor was calibrated with well characterized physical system consisting of a suspension of polystyrene spheres in DMEM. Next, the immobilization process of the cells onto various solid surfaces was characterized. A sedimentation rate and different arrangements of the cells at the gold and collagen surfaces were determined.. Specifically, the adhesion period followed by the cell proliferation time were measured, and unique signatures of the sensor response corresponding to each of these processes were identified. Finally, the cells were fixed with formaldehyde, which manifested itself with the increase of the cell elasticity and decrease of the viscoelastic losses. In conclusion, TSM piezoelectric sensors offer a very attractive technology platform for development of cell-based biosensors. Because a cell-based sensing process is physiologically relevant to natural cellular machinery, these sensor types will experience growing significance in the near future.