An Integrated Capacitive Array Biosensor for the Selective and Real-Time Detection of Whole Bacterial Cells

The rapid and selective detection of whole bacterial cells is of interest for the development of Point-of-Care (PoC) diagnosis tools. We present here an integrated capacitive array biosensor based on the AC impedance spectroscopy of interdigitated microelectrodes. The microelectrodes are integrated with a 0.25 µm CMOS process as the pixel element of a capacitive array. A capacitive-to-voltage conversion was designed below each pixel and the sensitivity is boosted by a subthreshold gain stage. The microelectrodes are coated by an ultrathin passivation layer and operated in electrolytes with bacterial cells adherent to the surface. Analytical models and two-dimensional simulations accurately assessed the device’s sensitivity. The simulations include the modeling of the sensor topology, the dielectric properties of multi-shell bacteria, the various ionic transports, and surface and space charges. The selectivity is provided by involving lysostaphin for genus-specific bacterial detection. The sample matrix is then directly flown on the polydopamine-covered sensor surface without any pre-treatment. The capacitive biosensor array performs dielectric measurement of the electrolytes and the real-time detection of Staphylococcus epidermidis binding events with a detection limit of about five bacteria per pixel