Plasmon Coupling Enhanced Micro‐Spectroscopy and Imaging for Sensitive Discrimination of Membrane Domains of a Single Cell

Different cell membrane domains play different roles in many cell processes, and the discrimination of these domains is of considerable importance for the elucidation of cellular functions. However, the strategies available for distinguishing these cell membrane domains are limited. A novel technique called plasmon coupling enhanced micro‐spectroscopy and imaging to discriminate basal and lateral membrane domains of a single cell combines the application of an additional plasmonic silver film for surface plasmon (SP) excitation to selectively excite and enhance the basal membranes in the near‐field with directional enhanced microscopic imaging and spectroscopy. The SP and critical evanescent fields are induced upon excitation through a silver‐coated semitransparent coverslip at the surface plasmon resonance and critical angles, respectively. The basal and lateral membrane domains located within the SP and critical evanescent fields can be selectively excited and distinguished by adjusting the incident angle of laser irradiation. Moreover, the brighter images and more intense spectra of membrane‐targeting fluorescence‐Raman probes under directional excitation than in conventional EPI mode allow clear identification of the membrane domains. By employing the additional plasmonic silver film for surface plasmon (SP) excitation to selectively enhance the fluorescence‐Raman signal from the basal membrane in the near‐field, plasmon coupling enhanced microscopic technique is capable of selectively exciting the basal and lateral cell membranes at the surface plasmon resonance (θSP) and critical (θC) angles, respectively. The brighter micro‐images and more intense micro‐spectra of the probes bound to basal and lateral cell membranes in SP and critical excitation modes than in conventional EPI mode allow the membrane domains to be clearly distinguished.