Biomedical engineering at The University of Memphis.

Members of the Biomedical Engineering Department in the Herff College at The University of Memphis are active in several areas of biomedical technology. As a part of the NSF Center for Biosurfaces, our faculty operates a laboratory for Nanoindentation Studies and a Laboratory for Studies of Protein Deposition. Our faculty group that is interested in electrophysiological events and related medical devices measures and models events related to heart and neural function. As engineers interested in measurements and related devices, we work to develop and deploy biosensors--electrical devices that function because they include enzymes or other biological compounds. As individuals interested in long-term proper function, we perform studies to show how deposition of proteins on surfaces alters the way materials respond to blood exposure and implantation and how cells are activated on exposure to stresses of flow. We also study stretching and other deformations of soft and bone tissues, with goals that range from measuring the strength of a healing, sutured wound to providing a mathematical model of pulmonary function and predictions related to traumatic chest injury. Our efforts are led by individual talented faculty, spurred on by inquisitive student researchers, and often are collaborations with colleagues and partners in the University and the Memphis community.

Microfabricated chemical and biological sensors serve as an interface between biologic and electronic systems; they provide a means to transform specific chemical information into proportional electronic signals. Microfabricated electrochemical sensors have been used in acute and chronic biomedical monitoring of important physiologic parameters of human health both in vitro and in vivo. Current projects of the Biomedical Engineering Department include:

* Developing multi-analyte sensing devices (e.g., for the detection of cardiac markers) and enzyme activity sensors (e.g., for electrochemical immunoassays and bedside/doctors office test strips).

* Reducing the size of ion sensors for in vivo or in-line monitoring (e.g., continuous monitoring of sodium and glucose concentration of patients with diabetic glycoacidosis).

* Improving the detection limit of ion sensors to extend their application to sub-micromolar concentration (e.g., monitoring of heavy metals in biological and environmental samples).

* Developing reflection-based optodes (optical electrodes) for high throughput screening and simple ion concentration measurement at tissue surfaces.

* Characterizing sensor materials with respect to their biocompatibility (protein adsorption).

Electrical activity in the body needs to be understood to depict function of physiological systems like the heart, brain, and muscles, to develop and improve monitoring equipment for use in hospitals, outpatient clinics, and, increasingly, home care, and to design and test implanted devices like cardiac pacemakers and defibrillators. One group of faculty is interested in physiologic and computational electrophysiology (PACE) for such applications. They concentrate on:

* Improving life-saving devices called defibrillators. Sudden cardiac death, also called a massive heart attack, is the leading cause of death in America. About 300,000 Americans die each year from sudden cardiac death. Immediate defibrillation is the only effective treatment. That's why defibrillators can now be found in airplanes, shopping malls, and stadiums. For those at very high risk of sudden cardiac death, a defibrillator can even be implanted in their body.

* Despite the prevalence of defibrillators these days, there is relatively little known about how a defibrillator saves lives. The group studies how sudden cardiac death starts as well as how the defibrillator saves the patient. This research could lead to a defibrillator that is smaller, safer, and saves more people. The group has also developed an anatomically realistic computer model to simulate the electric shocks during defibrillation.

* Understanding biologic cell function using computer models. The group studies how cell functions change during development and aging as well as under disease conditions such as diabetes and chronic heart failure. This research can have direct impact on new drug treatments. The group also uses the computer models as instructional tools in the graduate program in Memphis and at other universities.

Nanoindentation is a small-scale method that permits measurements of mechanical material properties (especially hardness and elasticity) for local (5 micrometer) in-surface regions and the examination of bonding of thin layers with lower substrates. Nanoindentation was and continues to be widely used for research to improve magnetic recording media used in items like hard drives for personal computers. The University of Memphis Laboratory for Nanoindentation has allowed faculty in several departments (e.g., Biomedical Engineering, Mechanical Engineering, Physics) to make measurements related to their studies related to materials science. Materials include polyethylenes for implantation, human and mouse bones, and implantable metallic materials. For bones and many materials, the region tested by typical indentation methods is so large that many features are averaged in each test. Nanoindentation allows specific regions to be tested (e.g., a lamella in a Haversian canal around a bone cell, or a local region of a polymer that is known to have a larger microstructure). Recent work that made measurements on tibia from two strains of inbred mice, which are used for bone research and for which much past genetic knowledge is available, suggested that the quantitative trait loci (QTL, the chromosomes associated with specific traits) can be identified by statistical analysis of the mechanical data that were obtained with nanoindentation technology. One known QTL was identified by the data and three others of similar statistical significance found. The technology appears to offer a novel approach to showing genetic loci and the linked biomolecular species that would be well suited for studies to understand what controls the matrix properties of bone.

Proteins, other biochemicals, cells, tissues, and, indeed, whole living systems are often studied in deliberate ways for specific ends. Examples of such studies show a broader aspect of biomedical engineering and often involve wide collaborations. Ongoing efforts include:

* Platelets, a cell fragment needed for proper clotting of blood, have surface proteins, the integrins, which trigger reactions for the clotting process. Platelets are sometimes viewed as bag-like collections of strong biochemicals that become available for the clotting reactions after triggering by an integrin. Stress, e.g., flow through narrowed vessels or in a test device called a viscometer, can trigger the platelets. So can protein deposition on a catheter or other blood-contacting device. Studies to measure and understand these processes exemplify efforts related to cellular function and devices.

* Healing occurs as waves of cells perform their specific functions to restore mechanical integrity. A group of cells first clears the area of bacteria and debris. Other cells move in to build a matrix of proteins and fibers that will join the two sides. Still other cells provide blood circulation so there is continuing nutrition and maintenance of the biochemical environment. Drug regimens can interfere with or aid this healing process. Surgeons and patients need to know how quickly and reliably the healing process will occur. Mechanical studies of the strength of tissues like skin are special because skin stretches different amounts in different directions. Studies of skin stretching in rodents maintained on specific treatment protocols allows the stretch response to be correlated with the treatments. The goal is to demonstrate specific treatment protocols that avoid delayed recovery of mechanical strength of the sutured area.

* Function, as people are dependent on large, global systems, e.g., the neuromuscular system, for control of gait and the pulmonary system for maintenance of body condition. The initial view is that simple numbers characterize such physiological systems, e.g., a step length or a breathing rate. A closer view shows that we automatically take steps of the needed size to maintain balance, to reach a goal without needing a half-step. For the lungs, we occasionally sigh and restore balance; we will rebalance our supply of carbon dioxide, which is produced as tissues use the oxygen brought in by the lungs, so the pH of the body remains in balance. Many mechanical aspects of these automatically self-controlling systems are of interest to physicians as a part of diagnosis and treatment and to scientists who wish to better understand the body as a controlled system. Engineering methods and instrumentation for measurement of function and for analysis of the resulting data provide robust ways to observe and determine the function of such living systems.

Faculty of the department are interested in collaborations with researchers in local industry and other organizations; we expect to work with our community to reap the benefits that lie in further developing bio- and biomedical technology. Specialized instrumentation, e.g., the nanoindenten which is one of 300 worldwide, is available for use in specific studies by arrangement with the Integrated Microscopy Center and the BME Department; these arrangements cover the cost of equipment use.