optical based resonant waveguide grating RWG Cells are directly cultured onto the surface of a resonant waveguide grating (RWG) biosensor. The mass redistribution within the bottom portion of cells, mediated by stimulus is directly measured with the biosensor. RWG biosensor utilizes an optical beam with an appropriate angular content to illuminate a waveguide film in which a grating structure is embedded. When this beam is reflected by the sensor surface, the resonant angle dominates in the output beam. The mass redistribution within the sensing volume alters the incident angle. Because of its ability for multiparameter measurements, the biosensor has potential to provide high information content for cell sensing. These parameters include the angular shift (one of the most common outputs), the intensity, the peak width at half-maximum (PWHM), and area of the resonant peaks.