Plasmon-Based Nanowire Single Live Cell Endoscopy

Physically or optically addressing site-specific areas of a single living cell with high spatial resolution is the key approach for a better understanding of cellular behavior. To this end, cell endoscopy is one of the most attractive techniques as it enables to site-specifically tackle the intracellular environment. In conventional cell endoscopy, several probes, such as glass pipettes, glass fibers, nanowires, and nanotubes, are inserted into a cell, allowing optical studies, material delivery, electrochemistry, and so on. Optical waveguide probes are increasingly popular because they allow optical information to be easily directed to, and extracted from, the cell. However, the diameter of the conventional optical nanoprobes is still diffraction limited and its insertion is often invasive for the cell. On the other hand, plasmonic silver nanowires have great potential to overcome these problems and perform sub-diffraction-limited optical endoscopy. This chapter will explain the unique plasmonic property of metal nanowires, the surface engineering of metal nanowires for cell endoscopy, the basic principles of plasmon-based nanowire endoscopy, and a demonstration of the possible bio-medical applications (such as site-specific investigation of intracellular molecular interaction of endogenous molecules and tracking of intracellular pH).