Multi-photon microscopy exploits a phenomenon where fluorophores simultaneously absorb multiple photons of light to provide the energy required for an excited state. Typically this is acheived with light at double or triple the wavelength used for 'normal' fluorescence excitation i.e. a fluorophore that excites around 500 nm using standard excitation will exhibit 2-photon excitation at ~1000 nm. The multi-photon effect requires very high photon density, so a very high power laser is needed (pulsed lasers are the only practical option) and the effect is only seen at the plane of focus making multi-photon microscopy an inherently optical sectioning method. The longer wavelengths of light used for multi-photon imaging are beneficial for biological applications as infrared light is scattered and absorbed much less by biological tissue than visible light. This means that it's possible to image at depths in excess of 500 microns in live tissue, making multi-photon microscopy the method of choice for intravital imaging.
The Imaging Facility has a Nikon AX-MP mutli-photon microscope equipped with a dual laser system, and is optimally configured for intravital imaging applications. Please contact us for further details.
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