Julie A. Stenken Associate Professor Physical/Analytical and Biochemistry/Biophysics Cogswell 133 518.276.2045 stenkj@rpi.edu

Julie Stenken received her B.S. from the University of Akron and her Ph.D. in Bioanalytical Chemistry from the University of Kansas. During the 1994-95 academic year, she was a J. William Fulbright Fellow at the Karolinska Institute in Stockholm, Sweden. Prior to joining the faculty at RPI, she was a postdoctoral research associate in the Department of Pharmacology at the University of Kansas Medical Center. In 2000, she received an NSF CAREER award. During the fall of 2000, she was a Visiting Professor in the Department of Biomedical Engineering at Duke University.

The development and improvement of analytical methods to measure and quantitate biological molecules that reside in complex biological matrices is a principal focus of the Stenken group. To achieve this goal an understanding of analytical chemistry and biochemistry is important to our research. Our research principally uses microdialysis sampling coupled to chromatographic separations methods.

1. Enhancing Microdialysis Sampling Relative Recovery

Microdialysis techniques have been applied extensively to neuroscience research for sampling hydrophilic neurotransmitters from the extracellular fluid space of animals and humans. Using cyclodextrin binding chemistry, we continue to improve the sensitivity and broader applications of microdialysis sampling to solving in vivo analysis problems.

2. Quantitation of the Foreign-Body Response

Large companies resist developing, marketing, and investing in sensors for long term in vivo monitoring because of the difficulties in achieving reliable long term sensing due to surface fouling problems or calibration changes. Many of the problems that have been encountered in the development of in vivo sensors have been due to the lack of understanding of the host response to implanted materials. Our research is focused on understanding the local signaling chemistry (nitric oxide and leukotriene release) associated with the biointerface to an implanted material. Our long term goal is to use microdialysis sampling for real-time in vivo monitoring of the biochemical signals that are emitted during a host/biomaterial inflammation response.

3. Oxidative Stress - Measurement of the Highly Reactive Hydroxyl Radical

Oxygen free radicals (OFRs) are suspected in playing a central role in pathological processes including Parkinson's disease, cancer and aging. Hydroxyl radical (•OH) readily reacts with many important biomolecules, including DNA, membrane lipids, proteins, carbohydrates, and a variety of low molecular weight species. To assess the damaging role of •OH, it is important to be able to measure •OH concentration accurately. Hydroxyl radical is extremely reactive and its reactivity is under diffusion control. In collaboration with Professor Joseph Warden, we are developing more sensitive electron spin resonance (ESR) techniques for •OH quantitation. In addition to ESR, this project involves using liquid chromatography and electrochemistry for confirmation of ESR measurements. Recently, LC-MS has been extensively used for structural determination •OH products with newly developed commercially-available spin traps.

4. On-line analytical methods for anesthesia monitoring

Anesthesiologists use their own experience coupled with monitoring various vital signs such as heart rate, blood pressure, respiration, oxygen saturation, and patient response to determine the dose of anesthetics given during surgery. The practice of anesthesia is still plagued by problems of overdosing, underdosing, and patients waking up during surgery. Since drug effects are related to drug concentration, the ability to measure drug concentrations rapidly and feed this information as quickly as possible to the physician is extremely important. In collaboration with Professor Wayne Bequette's group in Chemical Engineering (RPI) and Dr. Rob Roy at Albany Medical College we are developing microdialysis sampling and fast analytical techniques to control depth of anesthesia. Microdialysis sampling of hydrophobic drugs such as the anesthetic, propofol, is being coupled to ultrafast-liquid chromatographic analysis to allow for real-time concentration measurements (less than 1 minute) to be included in the control models.

K.L. Snyder, C.E. Nathan, A. Yee, and J.A. Stenken, Diffusion and calibration properties of microdialysis sampling membranes in aqueous and protein solutions. Analyst, 2001, 126, 1261-1268. (Invited Research Paper)

J.A. Stenken, R. Chen, and X. Yuan, Influence of geometry and equilibrium chemistry on relative recovery during enhanced microdialysis. Analytica Chimica Acta, 2001,436, 21-29

J.A. Stenken, D.M. Holunga, S.A. Decker, and L. Sun. Experimental and theoretical microdialysis studies of in situ metabolism. Analytical Biochemistry, 2001, 290, 314-323.

A.N. Khramov and J.A. Stenken. Enhanced microdialysis extraction efficiencies of some tricyclic antidepressants and structurally related drugs by cyclodextrin-mediated facilitated transport. Analyst, 1999, 124, 1027-1033.

A. N. Khramov and J. A. Stenken. Enhanced microdialysis extraction efficiency of ibuprofen in vitro by complexation with b-cyclodextrin. Analytical Chemistry, 1999, 71, 1257-1264.

J.A. Stenken. Methods and issues in microdialysis calibration. Analytica Chimica Acta, 1999, 379, 337-358. (Invited Review)