The bright field (a) and SPRM (b) images of a SH-EP1 cell. (c) The epifluorescence image of the same cell stained with Alexa Fluor 555 labeled WGA with focusing on the bottom cell membrane portion. White arrows indicate the borderline between the thick cell body (in the center) and the thin cell membrane (in the edge). (d) SPR sensorograms of the entire cell region (black curve), cell edge region (red curve) and cell central region (blue curve) during the binding and dissociation of 80 μg/mL WGA. (e) SPR sensorograms of the cell edge region (black curves) and the global fitting (red curves) with WGA solutions of different concentrations (from bottom to top: 5, 10, 40, 80, 200 μg/mL). (f) The equilibrium-based dissociation constant (KD) was determined to be 0.32 μM by plotting the concentration dependent equilibrium responses.