COMBINED IMAGING AND CHEMICAL SENSING USING A SINGLE OPTICAL IMAGING FIBER

Despite many innovations and developments in the field of fiber-optic chemical sensors, optical fibers have not been employed to both view a sample and concurrently detect an analyte of interest. While chemical sensors employing a single optical fiber or a noncoherent fiber-optic bundle have been applied to a wide variety of analytical determinations, they cannot be used for imaging. Similarly, coherent imaging fibers have been employed only for their originally intended purpose, image transmission. We herein report a new technique for viewing a sample and measuring surface chemical concentrations that employs a coherent imaging fiber. The method is based on the deposition of a thin, analyte-sensitive polymer layer on the distal surface of a 350-mu m-diameter imaging fiber. We present results from a pH sensor array and an acetylcholine biosensor array, each of which contains similar to 6000 optical sensors. The acetylcholine biosensor has a detection limit of 35 mu M and a fast (<1 s) response time. In association with an epifluorescence microscope and a charge-coupled device, these modified imaging fibers can display visual information of a remote sample with 4-mu m spatial resolution, allowing for alternating acquisition of both chemical analysis and visual histology.