Real-time monitoring of transplant organs

Human organs deteriorate rapidly without free-flowing blood. The condition, known as ischemia, can be a problem during surgical operations or the transport of graft organs. MICROTRANS’ answer is a small silicon needle with multiple sensors, capable of continuously measuring the electrical impedance of tissues.

Heart surgeons carefully monitor a beating heart on an electrocardiograph. But if they need to artificially stop the heart during a procedure, these measurements may be lacking for as long as 30 minutes.

In the MICROCARD project, an earlier project funded under the European Commission’s ESPRIT programme, European researchers tested a system that continuously monitors the condition of organs. They came up with a needle-shaped microsensor, carved from a silicon wafer, for inserting directly into an organ. Its chemical sensors assessed parameters such as pH and potassium, but were more accurate in chemical solutions than in living tissues.

So in the follow-up three-year project MICROTRANS, researchers from four countries concentrated on developing and testing sensors that measure electrical impedance. Results showed these sensors are ideal for checking the health of organs during artificially induced ischemia – during cardiac surgery or when transported in a cool-box from the donor to the recipient, a period lasting up to 24 hours.

Doctors currently employ several methods to assess the effects of ischemia on transplant organs; none are very effective or accurate. Most transplant surgeons therefore rely on visual inspections to decide if an organ can be successfully transplanted or not.

The new system provides a much better picture of the organ. Just over a centimetre in length and a less than a millimetre wide, the tiny probe measures the temperature, pH, potassium and impedance of the tissues. “It is very robust and sensitive,” says Toni Ivorra, an electronic engineer from the Spanish company coordinating the project, CNM.

The project also developed a module for the cool-boxes used to carry transplant organs. It includes a radio transmitter which sends the probe’s readings to a personal digital assistant (PDA) mounted on the box. If the organ’s temperature rises too much during transport, the system will generate an alarm. At the destination hospital, the surgeon can check the PDA screen or download its data to a computer. The result, say the researchers, is fewer discarded organs and more successful transplants.

This silicon needle may have other niche applications. It could improve food security by monitoring the quality of meat, fruit and vegetables during their storage and/or growth phases.

Price should be no barrier to the commercialisation of this multiprobe microsensor, because the whole system is designed to be disposable. But Ivorra admits that transplant physicians may need convincing that electrical-impedance sensors are better than chemical ones.

Exploitation rights for the patented system are held by project partner Carburos Metálicos (Air Products). It is working with two other partners, i2m and the National Centre for Microelectronics of Barcelona, on an industrial prototype for testing in European hospitals and laboratories. If successful, a system comprising the transplant transport module, the needle, electronics and telemetry equipment could be on the market in two years.

Contact:
Professor Jordi Aguiló
CNM – CSIC
Centro Nacional de Microelectronica
Consejo Superior de Investigaciones Científicas
Campus Universitat Autònoma de Barcelona
E-08193 Bellaterra
Barcelona
Spain
Tel: +34-9-35947700
Fax: +34-9-358014 96
Email: jordi.aguilo@cnm.es