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Biosensor Brigade

Biosensor Brigade
Health Science Center and UTSA researchers work to create the perfect medical monitoring method

July 2005

by Will Sansom

A tiny patch of designer cells, strategically placed in the body, provides a continuous reading of insulin – with no need to prick a finger. Other groups of cells, precisely positioned, provide hourly readouts showing the level of a medication a patient is taking. The cells send signals to an output device the size of a wristwatch. Is it too far-fetched to imagine? Not according to researchers from The University of Texas Health Science Center at San Antonio and The University of Texas at San Antonio, who are working under a grant from the institutions’ joint San Antonio Life Sciences Institute (SALSI).

Peter J. Hornsby, Ph.D., professor of physiology at the Health Science Center, and Dhiraj K. Sardar, Ph.D, professor of physics at UTSA, are in the second year of a project titled "Noninvasive Tissue-Based Biosensors for Biomedical Research." "The idea is to develop a way to find out what is going on inside the body without drawing blood or doing other invasive tests," Dr. Hornsby said. "The heart of the biosensor will be cells that are genetically engineered to make the measurement – to turn the process we are trying to measure inside the body into a number that can be read outside the body on an output device the size of a wristwatch."

The cells might be seeded on a metallic or plastic platform an inch wide at most. "That is so this sensor could be implanted into the body in a very noninvasive sort of way," said Dr. Hornsby, a member of the Health Science Center’s Sam and Ann Barshop Institute for Longevity and Aging Studies.

The key to the project’s success will be converting information from the designer cells into a meaningful measurement of body function. Drs. Hornsby and Sardar have their eye on "bioluminescence," which means the cells will be engineered to produce light in response to a specific stimulus. The extremely low levels of light that are produced would then be converted to a radio signal via highly accurate, miniaturized output devices that the researchers envision will come to the market in the next few years.

Current experiments employ a fiber-optic cable to make the connection between a biosensor and an external monitor, but in this age of infrared beams that enable remotes to communicate with TVs, DVDs and VCRs, radio signaling technology can’t be far behind.

The envisioned biosensors could provide a post-menopausal woman and her physician with continuous monitoring of her estrogen level. One of the key hindrances to effectiveness of hormone replacement therapy is under- and overdosing of the estrogen.

"This is possibly a little science fiction, but on the other hand it’s not impossible," Dr. Hornsby said. "The key part of the biology is to engineer the cell to be able to detect something and to turn that signal into something else. We have chosen light because we believe it is a great way of measuring anything.

"The reason we teamed up with Dr. Sardar was he is an expert in biophotonics, the field in which light is applied to biological systems," Dr. Hornsby continued. "Dr. Sardar is very well respected and well known in that field. He understands what we want to do in terms of the electronics and physics."

Arlan G. Richardson, Ph.D., director of the Barshop Institute, which unites 160 researchers at the Health Science Center, UTSA, South Texas Veterans Health Care System, Southwest Foundation for Biomedical Research and U.T. Austin, called the biosensors project "tremendously innovative – there is nothing like it. I’m not sure how many people other than Peter Hornsby have ever conceived such a thing." Dr. Richardson is professor of cellular and structural biology and occupies the Methodist Hospital Foundation Chair in Aging Studies and Research at the Health Science Center. He also is senior research career scientist with the South Texas Veterans Health Care System.

Hormones change dramatically with age (estrogen decreases in the post-menopausal woman, for example) and the effects on cells over time are mostly unknown. "Levels of hormones change very quickly, which makes observing any effects very difficult," Dr. Richardson said. "The biosensors envisioned in this project would provide continuous information on hormone levels to give us valuable insight into age-related hormonal effects."

This is just one example of the important information that biosensors would communicate. Scientists would gain valuable insights about the human body without pricking a finger – yours or mine.

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Blueprint of a Biosensor



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