Detecting and Deciphering the Telltale Signs of Biomarkers

Posted on | July 5, 2011 | No Comments

Screening Biomarkers

Paul W. Bohn

  • Paul W. Bohn
    Arthur J. Schmitt Professor
    Chemical and Biomolecular Engineering

In Edgar Allen Poe’s “The Tell-tale Heart” the killer confesses because he believes the police officers visiting him can hear the beating of his victim’s heart, indicating that a crime had been committed. A fictional work, the concept of the human body sending signals has its roots in reality. All biological systems have “telltale” signs, biochemical signatures that when detected and correctly interpreted provide enormous insight into the state of an organism. It is these biomarkers — through the development of a nanoscale biofluidic transportation system — that a team of researchers at the University of Notre Dame and Purdue University is working to better understand.

“Our bodies give us signals every day,” says Arthur J. Schmitt Professor of Chemical and Biomolecular Engineering Paul W. Bohn, “many of which we cannot see. These signs are of vital importance in understanding how our bodies function and in learning how to address changes in health when cells are not functioning as they should.”

Bohn and a collaborative team of researchers from Notre Dame and Purdue are studying some of these signals and the cells that create them through a National Science Foundation Instrument Development for Biological Research grant focusing on lipids and oxidative stress.

Oxidative stress, an imbalance of oxygen in the body, plays a significant role in many conditions, such as atherosclerosis, lupus, Niemann-Pick (type C), Parkinson’s, heart failure, and Alzheimer’s. It can often be detected first in damage to lipid processes.

Bohn Research Image

The Notre Dame-Purdue team is designing and testing a biomolecule fluid transfer and analysis system for the contin-uous monitoring of biomarkers that centers around a miniature mass spectrometer. The system would provide in situ screening of a range of biomarkers, specifically concentrating on lipid transformation in relation to oxidative stress. The junction between the device and the mass spectrometer employs desorption electrospray ionization (DESI) via a discontinuous atmospheric pressure interface (DAPI). The heart of the mass spectrometer is a rectilinear ion trap (RIT).

Bohn Research Image

The illustration (A) and photo (B) show the device structure and layers of a multi-stage microfluidic device that allows for multidimensional separations.­ The team is applying this structure to their research into oxidative stress.

The main functions of lipids are energy storage, cell membrane structure, and cell signaling (to bind proteins). However, there is not a quick and practical method with which to profile the range of lipids within the body. Current technology can only identify the activity of a single species at a time and then only after detailed sample preparation, processing, and data analysis.

The multi-stage microfluidic system (lab-on-a-chip) the team is designing will allow them to collect very small samples of biofluids, separate them into chemically distinct components (different classes of lipids) using electrokinetic transport in a nanofluidic-microfluidic emitter chip, and then compare the ionization of all of those components in situ — their telltale signs — with more detail and accuracy.

“Lipids, because of the range of their biomarkers and relevance to biological processes, are ideal for our purposes,” says Bohn. Working together with Bei Nie in Notre Dame’s Advanced Diagnostics and Therapeutics initiative, Bohn’s group has developed some exciting new multi-dimensional approaches that allow lipids to be probed simultaneously by chemically orthogonal measurements — in this case inelastic light scattering to unveil details of the chemical structure and laser desorption-ionization mass spectrometry to reveal molecular mass. By combining the two it should be possible to assess subtle changes in the molecular structure of compounds that are produced in response to oxidative stress, leading to an ability to form a unique MS-Raman chemical fingerprint that can characterize even small changes in cellular composition and signal the early stages of lupus, multiple sclerosis, and other neuroinflammatory diseases.

Suggested Reading

Kim, Bo Young; Yang, Jing; Gong, Maojun; Flachsbart, Bruce R.; Shannon, Mark A.; Bohn, Paul W.; and Sweedler, Jonathan V., “Multidimensional Separation of Chiral Amino Acid Mixtures in a Multilayered Three-dimensional Hybrid Microfluidic/Nanofluidic Device,” Analytical Chemistry, 2009, 81, 7, 2715-22.

Kim, Bo Young; Swearingen, Carla B.; Ho, Ja-an A.; Romanova, Elena V.; Bohn, Paul W.; and Sweedler, Jonathan V., “Direct Immobilization of Fab’ in Nanocapillaries for Manipulating Mass-limited Samples,” Journal of the American Chemical Society, 2007, 129, 24, 7620-6.

Iannacone, Jamie M.; Jakubowski, Jennifer A.; Bohn, Paul W.; and Sweedler, Jonathan V., “A Multilayer Poly(dimethylsiloxane) Electrospray Ionization Emitter for Sample Injection and On-line Mass Spectrometric Detection,” Electrophoresis, 2005, 26, 24, 4684-4690.

Tulock, Joseph J.; Shannon, Mark A.; Bohn, Paul W.; and Sweedler, Jonathan V., “Microfluidic Separation and Gateable Fraction Collection for Mass-limited Samples,” Analytical Chemistry, 2004, 76, 21, 6419-6425.

Kuo, Tzu-C.; Kim, Hee-K.; Cannon Jr., Donald M.; Shannon, Mark A.; Sweedler, Jonathan V.; and Bohn, Paul W., “Nanocapillary Array Membranes Effect Rapid Mixing and Reaction,” Angewandte Chemie International Edition, 2004, 43, 14, 1862-5.

Kuo, Tzu-C.; Cannon Jr., Donald M.; Chen, Yanning; Tulock, Joseph J.; Shannon, Mark A.; Sweedler, Jonathan V.; and Bohn, Paul W., “Gateable Nanofluidic Interconnects for Multilayered Microfluidic Separation Systems,” Analytical Chemistry, 2003, 75, 8, 1861-7.

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