Nanoscale investigation of cell-membrane by a highly sensitive near-field scanning optical microscope

초록

We report on the nanoscale investigation (􀂔100 nm) of epidermal growth factor receptor (EGFR) distribution on the membrane of A431 cancer cells immersed in a phosphate buffered saline solution by constructing highly sensitive near-field scanning optical microscope (NSOM), which achieved an extremely high Q factor of about 2,800 in liquid. The highly sensitive NSOM was implemented by introducing two position-controllable nodal wedges into a conventional NSOM probe [1] and its advantageous resonant characteristics in liquid environment were investigated by numerical analysis and experiment. The anti-EGFR conjugated gold nanoparticles were labeled to the EGFRs for the nanoscale NSOM imaging, and the sample was illuminated by a 405 nm laser from the side. Then, the scattered light from the anti-EGFR conjugated gold nanoparticles was collected by a NSOM probe with scanning the cell membrane as described in Fig. 1. From a measured NSOM result in aqueous environment, the average size of EGFR clusters on the cell membrane was estimated about 150 nm2. In a case of measurement in air, on the other hand, this clear EGFR distribution could not observed due to the receptor aggregation by a contraction of cell.