Fiber optic and clinical applications of near- and mid-infrared spectroscopy

Novel fiber optic and clinical applications of near- and mid-infrared spectroscopy have been investigated. Multivariate data analysis has been employed for both qualitative and quantitative applications. Three applications of fiber optics in near- and mid-infrared spectroscopy have been investigated. The fiber optics were used both as a waveguide to transmit light from and to a spectrometer and as an intrinsic element of a sensor. Evanescent wave absorption (attenuated total reflection ATR) spectra in near- and mid-infrared regions were used for detection. (1) A pH sensor was constructed with silica fiber by immobilizing a conductive polymer onto the core of the fiber. The evanescent wave spectrum of the conductive polymer in the 1100-1450 nm region was used to monitor the effect of pH. Non-linear P-matrix regression of the absorbance at 1428 nm was used for pH prediction. (2) ATR and bio-glucose sensors in the mid-IR region were made from chalcogenide fibers. The ATR sensor used the fiber core to measure the evanescent wave spectra of glucose samples; the biosensor was constructed by immobilizing a glucose oxidase on the core of the fiber. Results from two sensors were very similar. (3) A chalcogenide fiber was also used to monitor lamination processes in an autoclave. The evanescent wave spectra were measured by embedding the fiber optic in a laminate package. The degree of cure was determined by the absorbance changes in specific absorption bands. Near- and mid-infrared spectroscopy has also been applied to Pap smear analysis and lung surfactant analysis. Near-infrared spectra of Pap smears with normal and abnormal cervical cells were measured. Principal component analysis (PCA) and discriminant analysis were employed to classify these spectra and can separate normal and abnormal Pap smears. Near- and mid-infrared spectra of natural lung surfactant (LS), calf lung surfactant extract (CLSE) and the main phospholipid of LS, DPPC, were studied; the effects of Ca$\sp{2+}$ on these complexes were also investigated. The microstructures of the LS complexes were predicted based on the spectral differences