Principles and commercial instruments of three distinct types of label-free biosensors. (a) Surface plasmon resonance, which uses light excited surface plasmon polaritons to sense whole cells. Biacore SPR T200 and GWC SPRImagerII are two examples of commercial products. (b) Resonant waveguide grating, which uses leaky mode nanograting waveguide structure to generate an evanescent wave to sensor whole cell responses. Epic, EnSpire, and BIND are three commercially available products. (c) Electric biosensor, which uses a low electrolyte impedance interface to sense whole cell responses. ECIS, xCELLigence, and CellKey are three commercial products.
