Higuchi Biosciences Center - University of Kansas

Miniaturization of Separation-based Biosensor Components
“We make things small because they are easier to move”.

HBC participating scientist Dr. Susan Lunte likes things small.

Lunte is the newly named Ralph N. Adams Distinguished Professor of Chemistry and Pharmaceutical Chemistry. Her area of research interest is bioanalytical chemistry, with focus on liquid chromatography, capillary electrophoresis, electrochemical and laser-induced fluorescence detection, microdialysis sampling, pharmaceutical analysis, neurochemistry, protein and peptide analysis. These are all ways to study the tiny amounts of chemicals (analytes) of interest in samples such as blood. She currently is working toward two goals—to develop ways to find even smaller amounts of biological items of interest and to create smaller tools to study those biological items.

Lunte’s research efforts help in the effort to develop new or improved medicines. Understanding how peptides change and move as these travel across biological barriers is essential in effective drug design and in the understanding of neurological disorders. Crucial to this understanding is developing analytical methodologies that are able to monitor peptides, amino acids, neurotransmitters, and drugs at minute, physiologically relevant concentrations. The Lunte research group is focused on the developing these sensitive and selective analytical methods that can detect in biological fluids biologically important compounds. Lunte uses cell culture models in test tubes (in vitro) or biological samples obtained with microdialysis sampling (in vivo) to study the release, transport and metabolism of these substances. Ultimately, the analytical methods Lunte develops will be used to test samples of blood and other biological materials the medical community collects from patients. Doctors and nurses of course strive to gather as small a sample as possible from a patient.

Due to the small sample volumes generated by cell cultures and microdialysis, microcolumn methods have been employed for the separation of those analytes of interest—peptides, neurotransmitters, etc. The separation method capillary electrophoresis has been most thoroughly explored due to its small sample volume requirements and ability to perform fast, highly efficient separations.

Then once the analyte of interest is separated from the rest of the sample, ultrasensitive detection methods must be developed to determine the amount of peptides and other analytes at these physiologically relevant concentrations. Dr. Lunte and her associates concentrated primarily on the use of laser-induced fluorescence and electrochemical detection to obtain the requisite sensitivity. For example, they have used re- and postcapillary derivatization (transforming a chemical compound into a product of similar chemical structure called a derivative) with laser-induced fluorescence detection for determination of substance P and its metabolites in microdialysis samples.

The Lunte laboratory has also recently developed several dual electrode electrochemical detectors that permit the selective detection of analytes undergoing chemically reversible redox reactions; these analytes include Cu(II) complexed peptides, catecholamines and thiols.

Dr. Lunte's research group is thinking even smaller to continue these successful advances. They are working to develop a way to use on-line coupling of microdialysis with capillary electrophoresis to create a sensor. This sensor would be capable of monitoring pharmacological and neurochemical activities in awake, freely moving animals in near real time. The group has developed a number of “separation-based biosensors” using microdialysis sampling. These include the development of the first on-line determination of aspartate and glutamate by precolumn derivatization and capillary electrophoresis with laser-induced fluorescence detection.

The ultimate goal of the above research is the miniaturization of all of the components of the separation-based biosensor so that the system will be portable, resulting in a truly freely moving, untethered animal. Toward this end, they have been investigating the development of microchip electrophoresis with electrochemical detection. With electrochemical detection, both the detector and the potentiosat can be miniaturized. An added advantage is that the substrate need not be transparent for detection, so new materials can be investigated. Recently, the group has been studying the use of polymer based microchips for capillary electrophoresis/electrochemistry.

Lastly, the use of capillary electrophoresis/electrochemistry for clinical assays is being investigated. Plasma homocysteine has been proposed to be a potential early indicator of heart disease. The development of a fast and accurate analytical method that can be incorporated into the clinical laboratory or used for point-of-care testing is needed. Currently, the Lunte group is developing a microchip capillary electrophoresis/ electrochemistry-based system for the detection of homocysteine in plasma.

As the Adams Distinguished Professor, Dr. Lunte directs the Ralph N. Adams Institute for Bioanalytical Chemistry. This is an interdisciplinary consortium of researchers dedicated to achieving international leadership in Bioanalytical Science by fostering the highest quality research and education in the field of Bioanalytical Chemistry. As director, she joins with other institute researchers, to develop and use state-of-the-art sampling, separation, detection and characterization techniques—microdialysis, mass spectrometry, single molecule imaging and spectroscopy, microchip analytical devices, and electroanalytical techniques—to promote our understanding of fundamental life processes. This work also will increase our knowledge of how to intervene in those processes to regulate biological function and restore health. In addition, the Institute is focused on developing the enabling technologies necessary for expanding the capabilities of high throughput screening, development of whole cell assays for drug discovery, and working on new approaches for the study and early detection of diseases including cancer, stroke, AIDS and neurodegenerative diseases.

1. http://www.chem.ku.edu/adamsinstitute/index.shtml

Higuchi Biosciences Center
University of Kansas
2099 Constant Avenue
Lawrence, KS 66047-2535
785-864-5183
hbc@ku.edu