Biosciences Graduate Program

Mark A. Arnold, BS, PhD

Portrait

Professor of Chemistry

Contact Information

Office: 230 IATL
Iowa City, IA 52242
Office Phone: 319-335-368

Email: mark-arnold@uiowa.edu
Web: More About Dr. Arnold - Related Websites and Resources

Education

BS, Chemistry, Indiana University-Purdue
PhD, Analytical Chemistry, University of Delaware

Education/Training Program Affiliations

Biosciences Graduate Program

Research Summary

"My research program centers around the development, characterization and implementation of novel chemical sensing devices with a focus on solving analytical problems in biomedical science. Examples of sensors currently under investigation include 1) a near infrared spectoscopic sensor for the noninvasive measurement of blood glucose, 2) a biocatalyzed-chemiluminescent biosensing scheme to monitor directly the release and uptake of glutamate from synapses in brain slice preparations, and 3) novel biosensors based on unique gas-sensing designs. The concept of noninvasive blood glucose sensing involves passing a band of near infrared light through a vascular region of the body. The concentration of glucose is then obtained by analyzing the resulting transmission spectrum. In this project, the critical question is selectivity. Without chemical reagents or physical separations to enhance selectivity, all the required information must be obtained solely from the spectral information. Success of this approach depends on our ability to collect high quality spectra and to extract the analytical information. The issue of spectral quality requires an optical design with the highest possible signal-to-noise ratio. The highly scattering and strongly absorbing nature of the sample mandates particular attention to issues of source intensity and detector sensitivity. Even with the highest quality spectra, sophisticated data processing schemes are needed to extract glucose information from these spectra. Our research has demonstrated that accurate glucose information can be obtained from samples as complicated as whole bovine blood by combining digital filtering techniques and partial least squares multivariate calibration procedures. We are beginning to extend this approach to other measurement systems such as continuous in situ measurement of soluble components in bioreactors. A biocatalytic chemiluminscent biosensing scheme is being developed to quantify glutamate in brain slice preparations. Glutamate oxidase and horesradish peroxidase are combined to generate light at 430 nm from extracellular glutamate. Synaptic glutamate is monitored by positioning the brain slice in a perfusion chamber on the stage of a microscope equipped with a photon-counting detector system. Different concentrations of glutamate are indicated by different light intensities. Key issues currently under consideration are limit of detection as well as temporal and spatial resolution. This analytical system has been used successfully to measure the time-dependent release of glutamate from the hippocampus region of rat brain slices during potassium evoked depolarization conditions. Novel gas-sensing systems are being designed for the measurement of neuroactive compounds. For example, we have recently reported a novel sensor for nitric oxide measurements. Nitric oxide from the sample crosses a gas-permeable membrane and enters a recipient solution that contains hydrogen peroxide and luminol. The entering nitric oxide rapidly reacts with the hydrogen peroxide to form peroxynitrite which then reacts with luminol to generate light via a chemiluminescence reaction pathway. The intensity of the light is related to the concentration of nitric oxide in the sample solution. We are also interested in using our fiber optic ammonia sensing technology for measuring extracellular ammonia levels during neurochemical processes. Lastly, a flow injection analysis system is under development for rapid glutamate measurements. Our objective is to design a system capable of providing accurate extracellular glutamate values within thirty seconds."

Date Last Modified: 06/07/2014 - 21:56:23