The multi-photon microscope (MPM) is located in the Oxford Centre for Tissue Engineering and Bioprocessing for imaging tissue and bio-material constructs. In brief, the setup includes a Ti:sapphire laser (900 Mira, Coherent) tunable from 700nm to 1000nm, pumped by a 10W Verdi laser (coherent). The laser is sent through a multi-photon dedicated laser scanning system (Bio-Rad Radiance 2100MP) coupled to an upright microscope (Nikon E600FN). The upright configuration allows the use of high numerical aperture, long working distance water-dipping lenses where working distance can reach up to 2 mm. The direct detectors are non-descanned photomultiplier tubes thus the transmission path from the laser to the sample is highly efficient. Furthermore, the photomultiplier tubes are highly-sensitivity over the ultraviolet (UV) to near infra-red (NIR) range.
A spectral interferometer (SpectraCube®) sensitive over the mid-blue to red wavelength range can be used to spectrally characterize new/previously unidentified/mixed fluorescence signals in tissue. However, because of the current arrangement of the spectral detection system, in which a CCD camera is used for acquiring an image is currently not suitable for spectral characterization of fluorophore sources located deep in scattering tissue. The microscope has been sectioned in half allowing the transmission (bottom) half to be removed completely and the top half (mounted on three stainless steel arms) effectively float the microscope objective lens in mid-air. This accommodates a large animal (e.g. pig) on a surgical cart under the scope for conducting in vivo imaging.