Single gold-tagged epidermal growth factor (EGF) molecules bound to cellular EGF receptors of fixed fibroblast cells were imaged in liquid with a scanning transmission electron microscope (STEM). The cells were placed in buffer solution in a microfluidic device with electron transparent windows inside the vacuum of the electron microscope. A spatial resolution of 4 nm and a pixel dwell time of 20 μs were obtained. The liquid layer was sufficiently thick to contain the cells with a thickness of 7 ± 1 μm. The experimental findings are consistent with a theoretical calculation. Liquid STEM is a unique approach for imaging single molecules in whole cells with significantly improved resolution and imaging speed over existing methods.
First example of whole cells imaged in liquid using in situ LC-STEM. Chemically fixed COS cells were labeled with EGF-targeted gold nanoparticles and imaged using HAADF STEM. The paper also includes a discussion on the theoretical parameters of resolution and in situ beam broadening.
Keywords: Cells; Cellular Labeling; Nanoparticles; Resolution