Update on Implantable Sensors for Metabolic Monitoring

Progress has been made in a continuing effort to develop surgically implantable, biocompatible electrochemical- sensor arrays for continuous measurement of concentrations of analytes that play major roles in human and animal metabolism. This development at an earlier stage was described in "Implantable Electrochemical Sensors for Metabolic Monitoring" (ARL-0017), Defense Tech Briefs, Vol. 1, No. 4 (August 2007), page 28. To recapitulate: in the electrochemical-monitoring approach followed in this development effort, cyclic voltammetry, amperometry, squarewave voltammetry, or a combination of these techniques is used to measure the rate of catalytic oxidation of glucose by the enzyme glucose oxidase (GOX) in a reaction mediated by poly[vinyl pyridine Os(bipyridine)2Cl]- co-ethylamine (POs- EA), which is an osmium-based polycationic redox polymer. To ensure biocompatibility, the GOX is entrapped in a poly(ethylene glycol) diacrylate (PEGDA) hydrogel that has previously been demonstrated to be biocompatible.

Posted in: Briefs, Medical, Architecture, Biological sciences, Prostheses and implants, Polymers

Toward High-Performance Neural Control of Prosthetic Devices

A program of basic and applied research in neuroscience is dedicated to (1) advancing fundamental understanding of how the human brain plans and executes arm movements and (2) designing and building high-performance neural prostheses for controlling arm prostheses. The basic-research part of the program involves experiments on non-human primates by use of techniques of chronic-electrode-array electrophysiology, computational neuroscience, theoretical neuroscience, and observations of reaching behavior. The appliedresearch part of the program includes, as part of the effort to develop neural prostheses, an effort to decode (that is, to extract scientifically and prosthetically useful signals from) neural activity in real time, use the signals generated in the decoding process to move computer cursors, and utilize the knowledge thus gained to design and validate high-performance neural-prosthetic algorithms.

Posted in: Briefs, Medical, Mathematical models, Nervous system, Prostheses and implants, Biomechanics

Progress Toward Cell-Directed Assembly of Nanostructures

During 2007, progress was made on several fronts in a research program oriented toward developing capabilities for biocompatible and biomimetic self-assembly of nanostructures that could perform desired functions as interfaces between biological and nanotechnological systems ("bio/nano" interfaces). These capabilities are expected to contribute, in turn, to development of new classes of biotic/abiotic materials and to understanding of responses of cells to diseases, injuries, stresses, and therapies. The approach followed in this research has been one of striving to understand and exploit celldirected assembly (CDA).

Posted in: Briefs, Medical, Research and development, Assembling, Biomaterials, Nanotechnology

Implantable Electrochemical Sensors for Metabolic Monitoring

Arrays of electrochemical sensors that include specially coated (as described below) gold electrodes on flexible polyimide sheets have been fabricated and tested in a continuing effort to develop biocompatible, surgically implantable electrochemical-sensor arrays for continuous measurement of concentrations of analytes that play major roles in human and animal metabolism. The effort thus far has been oriented particularly toward developing sensors for monitoring one analyte — glucose — to enable improved treatment of diabetic patients. It is planned to extend this effort to the fabrication and testing of sensors for monitoring lactate and pyruvate and, eventually, to implement the concept of a single array that contains sensors for monitoring glucose, lactate, and pyruvate.

Posted in: Briefs, Medical, Sensors and actuators, Medical, health, and wellness

Portable Simulator for Training in Robot-Assisted Surgery

Aportable apparatus is being developed as a means of training surgeons in robot-assisted surgery, including laparoscopic and other forms of minimally invasive surgery. The apparatus can be characterized as a virtual reality system that includes not only a computer and a visual display subsystem, but also an electromechanical subsystem with which a surgeon in training can interact as though interacting with a console of the type used to control a laparoscopic, endoscopic, or other surgical robot.

Posted in: Briefs, Medical, Simulation and modeling, Surgical procedures, Robotics

Aptamer-Based Sensors for Detection of Proteins

Molecular aptamer beacons (MABs) are being investigated for use as rapid-signaling probe compounds for detecting specific proteins of interest (target proteins). In the MAB approach, one exploits a combination of (1) the molecular- recognition capability and high affinity of aptamers (defined below) with respect to molecules of interest and (2) the fluorescent- signaling transduction method of molecular beacon probes (also defined below) to enable real-time monitoring of target proteins. MABs could help to satisfy the increasing need for rapid, sensitive biosensing in diverse endeavors that include medical diagnosis, discovery of drugs, and homeland security. For example, rapid biosensing could enable early diagnosis and treatment of disease or rapid response to a chemical or biological attack.

Posted in: Briefs, Medical, Sensors and actuators, Medical equipment and supplies

Nanosensor Arrays for Detecting Breast-Cancer Compounds

Arrays of nanosensors for detecting biomolecules associated with breast cancer are undergoing development. It has been proposed to construct the arrays as silicon-based large-scale integrated circuits, each array containing possibly thousands of nanosensors, for rapid, simultaneous detection of molecules of many different species of interest. Some or all of the nanosensors in a given array could be based on a detection principle involving changes in electrical conduction in biofunctionalized nanowires. Alternatively, some or all of the nanosensors in a given array could be based on a detection principle involving changes in the vibrational resonance frequencies of nanocantilevers. By exploiting the experience of the semiconductor and microelectromechanical systems (MEMS) industries, it should be possible to mass-produce such nanosensor arrays at low cost. The development work thus far has included computational simulations of the operation of nanosensors based on the aforementioned detection principles, and fabrication and testing of individual nanosensors and small nanosensor arrays.

Posted in: Briefs, Medical, Integrated circuits, Sensors and actuators, Diagnosis, Production, Biomaterials, Nanotechnology

AFRL Study Defines Standards for Low-Level Chemical Agent Exposure

Results of a 5-year, $40 million effort to study chemical warfare agents will benefit military and civilian personnel alike, helping leaders in both arenas cope with events should a terrorist or combat attack that exposes people to toxic chemical agents occur. Dr. Stephen Channel, an AFRL research veterinarian and toxicologist, is heading the collaborative research effort between AFRL and US Army scientists. Based at the Army's Medical Research Institute of Chemical Defense and the Edgewood Chemical and Biological Center at the Army's Aberdeen Proving Grounds, Maryland, the work is in its final year.

Posted in: Briefs, Medical

AFRL Seeks Ways to Prevent Hearing Loss in Military Environments

In the 1988 movie "Good Morning, Vietnam," character Adrian Cronauer, a Saigon- based military disc jockey, performs an on-air skit in which he contacts an artilleryman in the field and offers to play a song for him. "Anything," the artilleryman screams into the phone, "Just play it loud!"

Posted in: Briefs, Medical

AFRL Teams With Indy Racing League® for Neck Protection

The bulletlike, open-wheel Indy racing cars hurtle around oval tracks at breakneck velocities, often approaching speeds of 220 mph or higher. While a crash at this speed is a violent, sometimes tragic event, it is nonetheless a key data source for AFRL researchers seeking ways to create a safer environment for Air Force (AF) fighter pilots during emergency ejection.

Instituting a practical alliance of human peril and scientific research, AFRL engineers are teaming with the Indy Racing League (IRL) to share crash impact and injury data. Indy car drivers wear a miniature earplug accelerometer (see figure) that records vertical, lateral, and longitudinal accelerations of the driver's head during a crash. "This data will provide valuable information for criteria and model validation," states Ms. Erica Doczy, biomedical engineer in AFRL's Biomechanics Branch. "We need reallive human injury data to validate our models and criteria. In the lab, you can't re-create that [trauma], so this is just one way to collect that data, because accidents do occur in the motor sports industry."

The data helps researchers learn more about the dynamics of a highspeed impact and the effects of acceleration and impact on a human's head and neck. Researchers typically create models based on manikin and cadaver testing, but data from living humans is essential for validating the models. With the availability of detailed information about the car's speed and movement, and how the driver's head reacts at each stage of a crash sequence, researchers no longer have to theorize about the exact nature and cause of head and neck injuries. "We'll know what the car did, we'll know what the driver's head did, and we'll have medical data (the end result), so it's a way of validating the entire [series of] criteria," explains Dr. Joseph Pellettiere, technical advisor for the Biomechanics Branch.

The agreement with the IRL builds upon AFRL's long-standing program for improving neck protection for AF aircrew members during all phases of flight, and especially during high-risk, emergency ejection. "We develop the injury criteria and guidelines for how a flight helmet should be developed in terms of its mass properties—such as weight, center of gravity, and location of night vision goggles or other systems— such that it's safe for crew members to wear," elaborates Dr. Pellettiere.

AFRL researchers routinely feed updated data to flight helmet designers and manufacturers, who use the data to create safer next-generation equipment. The researchers also recommend the development and availability of preejection instructions that tell pilots how to physically prepare for ejection, including directions for assuming correct body position and bracing. "New helmet programs are using our criteria now," Dr. Pellettiere points out. "They are making their designs [according] to the guidelines we provide." Both the F-35 Joint Strike Fighter and the Panoramic Night Vision Goggle programs are developing helmets based on AFRL-supplied impact and injury data.

Indy car drivers benefit from the crash data through revised safety and equipment requirements which, in turn, improve racing safety levels. The research team also shares results with the commercial automotive industry through conferences and universities, a practice that can prompt safety-related policy changes for auto manufacturers.

As both technology and policy continue to evolve, the AF must persist in its efforts to evaluate pilot safety. This ongoing need is reflected in the following example, which illustrates how today's heavier helmet, coupled with a revised physical profile for pilots, has increased the risk of serious neck injuries during ejection. To accommodate a broader physical range of females (who currently constitute about 18% of AF pilots), the AF reduced the minimum body-weight limit for pilots to 103 lbs, with an associated decrease in neck muscle size and strength. Helmet weight, however, increases as peripheral systems are added to pilot headgear. A typical (3 lb) flight helmet's weight can increase to nearly 5 lbs after extra items, such as night vision goggles, are installed. According to Ms. Doczy, "Two additional pounds may not seem like much, but during an ejection, it adds a significant amount of force on the pilot's neck."

In addition to realizing safety improvements, the AF expects to achieve significant financial savings as a result of AFRL's neck protection advancements. "The potential for cost savings is tremendous, since the AF invests several million dollars to train each pilot," Ms. Doczy affirms. In addition to lost training dollars, the federal government bears the burden of an injured pilot through hospital and rehabilitation expenses. Preventing injuries and fatalities during ejection would minimize such costs. Cost-related advantages aside, the key goal for AFRL's neck protection program engineers— adeptly expressed in their motto, "Always Come Home Safely"—is to develop technology and use it to keep aircrew safe, not only during ejection, but ultimately in all phases of operational flight situations.

Mr. John Schutte (Ball Aerospace and Technologies Corporation), of the Air Force Research Laboratory's Human Effectiveness Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at Reference document HE-H-05-04.

Posted in: Briefs, Medical