Two-photon and multi-photon measurement of analytes in animal and human tissues and fluids

A method of measuring an analyte present in animal tissue, comprising:

• providing animal tissue containing an analyte which is excitable by a plurality of photons at a first wavelength at which said animal tissue is substantially non-absorbing, which analyte fluoresces at a second wavelength upon being excited at said first wavelength;
• irradiating said animal tissue with radiation at said first wavelength so as to excite said analyte through absorption by said analyte of said plurality of photons of said radiation at said wavelength, wherein excitation of said analyte results in a fluorescent emission from said analyte of radiation at said second wavelength;
• detecting said emission at said second wavelength;
• and
• determining the concentration of analyte based on the detected emission.

A method of measuring an analyte present in a material, comprising:

• providing material containing an analyte which is excitable by a plurality of photons at a plurality of wavelengths at which said material is substantially non-absorbing, which analyte fluoresces at a different wavelength upon being excited at said plurality of wavelengths;
• irradiating the material with radiation at said plurality of wavelengths so as to excite said analyte through absorption by said analyte of a plurality of photons of said radiation at said plurality of wavelengths, wherein excitation of said analyte results in a fluorescent emission from said analyte of radiation at said different wavelength;
• detecting said emission at said different wavelength;
• and
• determining the concentration of analyte based on the detected emission.