Patent ID: 8095196

Claim:
A sensor probe for in-situ measurement of pH in a human tissue environment comprising: a hollow needle having a tip and a back end, the tip being insertable through tissue into the human tissue environment; an optic cable comprising a light conduit surrounded by a cladding, wherein a first end of the light conduit not covered by the cladding has an outer diameter substantially conforming to the inner diameter of the hollow needle, is inserted from the back end of the needle, and extends to within a predetermined distance of the tip to define a cavity within the tip, wherein the optic cable is fixed to the hollow needle with the cladding abutting the back end of the needle; a porous dye layer within the cavity adjacent to the first end of the light conduit, wherein the dye layer has a response to excitation light delivered through the light conduit that varies according to the pH of the human tissue environment; and an overcoat layer deposited on the dye layer, wherein the overcoat layer is ionically permeable and substantially opaque at a light wavelength corresponding to the variable response of the dye layer.