Near infrared spectroscopy for monitoring bioreactor components and chemiluminescent sensors for hydrogen peroxide, glucose, and nitric oxide

Analytical measurement strategies are developed for numerous analytes of biomedical interest. Glutamine and asparagine are measured independently in binary aqueous mixtures by using near infrared (NIR) absorption spectroscopy. In addition fiber optic chemical sensors are developed for hydrogen peroxide, glucose and nitric oxide.; Glutamine and asparagine concentrations are measured in binary aqueous media with NIR spectroscopy. Absorption spectra of these chemically similar compounds provide sufficient analytical information to achieve simultaneous and selective measurements. The best overall performance has been obtained by partial least-squares regression coupled with digital Fourier filtering over the spectral range of 4650-4320 cm{dollar}sp{lcub}-1{rcub}{dollar} for glutamine with a standard error of prediction (SEP) of 0.10 mM and a mean percent error of 2.00%. For asparagine, models over 4800-4250 cm{dollar}sp{lcub}-1{rcub}{dollar} provide a SEP of 0.18 mM and a mean percent error of 2.50%.; The molecular basis for NIR absorption bands in the 5000-4000 cm{dollar}sp{lcub}-1{rcub}{dollar} spectral range has been identified for chemical species dissolved in aqueous media. Combinations of stretching and bending vibrational models for C-H, N-H, and O-H groups are responsible for these bands. Temperature, pH and adjacent groups influence both position and shape of these absorption features.; A novel gas-sensing arrangement is introduced for measurement of hydrogen peroxide. During sensor operation, hydrogen peroxide crosses a gas-permeable membrane and enters an internal solution composed of horseradish peroxidase and a suitable co-substrate, thereby generating either a chemiluminescent or fluorescent signal. Excellent selectivity is demonstrated for hydrogen peroxide over ascorbic acid, uric acid and tyrosine. A corresponding glucose biosensor is demonstrated by immobilizing glucose oxidase at the sensing tip of the gas-sensing hydrogen peroxide probe. The resulting glucose biosensor is capable of accurate measurements in blood samples.; Nitric oxide is also measured by a fiber optic gas-sensing configuration. Nitric oxide enters an internal solution and reacts with hydrogen peroxide to form peroxynitrite which rapidly reacts with luminol to produce light. A mathematical model is derived to explain the temporal response of this sensor. The consumption of nitric oxide by ambient oxygen is considered and explains systematic errors in nitric oxide measurements in the presence of common biochemical species.