Development of a fluorescence-based fiber optic sensor for rapid detection of general anesthetics and other lipid-soluble chemicals

A method is demonstrated of fabricating sensors for the detection of general anesthetics and other lipid-soluble chemicals. Some lipid-soluble fluorescent dyes are sensitive to changes in order of lipid bilayers that depend on temperature. These dyes can also be used to monitor perturbation of the bilayer that occurs when anesthetics are partitioned between its two components. The sensor employs as a reversible indicator a hydrogel entrapping liposomes that contain a hydrophobic fluorescent dye. The gel is immobilized at the end of two optical fibers, one of which transfers exciting radiation from a remote lamp, and the other of which returns the fluorescence to a remote compact spectrometer coupled to a photodiode array detector. As the fluorescence emission spectrum of the dye employed shifts to longer wavelength upon fluidization of the lipid bilayers, an absolute determination of fluidity can be made by monitoring the ratio of emission intensity at two wavelengths. The sensor is sensitive to clinically relevant concentrations of a commonly used general anesthetic, and preliminary studies on the transducing liposome system indicate that it should be sensitive to all other general anesthetics, including alcohols