Development of a direct point electron beam exposure system to investigate the biological functions of subcellular domains in a living biological cell.

Electron microscopy studies have demonstrated that the diameter of a focused electron beam is small enough to probe or manipulate subcellular domains of a single biological cell. Here, we report the development of a direct point electron beam irradiation system to investigate the biological functions of subcellular domains in a living cell. Subcellular structures of a single living cell cultured on a thin film can be selectively irradiated by the point electron beam generated by our system. We have demonstrated controlled beam positioning capability to selectively irradiate 500 nm size structure with a point electron beam. We determined beam irradiation parameters that did not cause irreversible plasma membrane perforation after beam exposure and the irradiation caused intracellular Ca elevation in an irradiated neuronal cell. Since the neuronal cell express fine subcellular structures such as neurites, we tried to position a beam on the structure and observed a Ca wave originated from the intended point, which showed that our system had enough selectivity to target a subcellular structure. Point electron beam exposure is expected to be employed for various cellular stimulation protocols, and this enables the investigation of the biological functions of subcellular domains.