Researchers at the University of Ulster have developed tiny sensors that can measure the quality of organs used in transplants, writes Dick Ahlstrom
Demand for transplant organs far outstrips supply, so it is important that donor organs be kept in peak condition prior to surgery.
With the aim of improving the success of transplants, a research group in Northern Ireland has developed a measuring system that assesses any deterioration.
The work is under way at the University of Ulster, Jordanstown campus, in its Northern Ireland Bio-Engineering Centre (NIBEC). The centre was established in 1986. Dr Christiaan Barnard, the South African surgeon who conducted the first heart transplant operation, opened its new EU- funded building in 1994.
The centre is involved in two related projects, MicroCard and MicroTrans, both funded under the EU's Esprit programme. The goal is to develop a way to ensure that organs made available for transplant remain healthy, explains Dr Eric McAdams.
"Organs are often transported over long distances from the donors to the patients," he says. "They are carried in what are essentially elaborate cooler boxes, and surgeons have to determine if the organs are in a suitable condition when they arrive in the operating theatre."
The goal is to develop a system that allows the surgeon to know immediately whether the organ is fit for transplantation or whether its condition has deteriorated during the journey.
"At the moment, the decision is made by inspection, but anything that gives them a better impression will increase transplant success," says Charlie Mahony, a UU research officer and member of the research team, which includes Prof Jim McLaughlin.
The projects arose from a collaboration between Dr McAdams and Prof Jordi Aguiló of the Centro Nacional de Microelectronica at the Autonomous University of Barcelona.
The work involves the development of flexible polymer-based microprobes, explains Mahony. These are implanted into the organ tissue and measure certain extra-cellular parameters.
"They are relatively small, about a millimetre wide and 10 to 15 millimetres long," says Mahony. "They are made from polyimide and are about as flimsy as a piece of cellophane from a pack of cigarettes."
The probes provide information by measuring "impedance", the resistance to a flow of electricity between two separated terminals. In this case the terminals are separated by a few millimetres on the implanted probe.
The technique developed at UU is known as "complex impedance spectroscopy", he says. The spectroscopy in the title refers to the fact that impedance is sampled at a wide range of frequencies, ranging from about a tenth of a hertz per second, a measure of frequency, down to one million hertz per second.
"By doing that spectroscopy we can sweep through the frequencies so we can get a good idea of the component we are measuring in the tissue," says Mahony. "This gives more information and is a lot more sensitive than simply measuring the conductivity."
Refinement of other probes for monitoring transplant organs parallels this work, devices that will measure things, such as temperature or concentrations of ions of potassium, sodium and calcium. The challenge is to make them as small as possible, something on the scale of the impedance probe.
Development of a good quality measure of organ condition would provide other benefits, Mahony suggests. It could help the researcher find the best possible conditions for storage and transport of donor organs. The team is also trying to produce an "ischemic non- viability index" that will provide meaningful definitions for organ quality, he adds.
NIBEC is working on other equally exotic projects. One involves the development of stimulation sensors that might help patients with permanent nerve damage to regain some limited movement. It is a process called "functional electrode control", says Mahony.
Still in its early stages, the idea is to place a microprobe close to a target nerve cell. Electrical stimulation causes the nerve to react, causing muscle movement. Initially, only limited movement is the goal - for example, enabling a person to trigger a nerve to control finger movement to throw a switch.
This would also be a useful way to help exercise muscles, but the team is looking for more.
"It does maintain muscle condition, but our main thrust is for the external control of muscles," adds Mahony.