The anti-epileptic device is a tiny transmitter three times the width of a human hair that is implanted below the scalp to detect the signs of an epileptic seizure before it occurs. The system is designed to record neural signals relayed by electrodes in various points in the brain. The electrodes would be inserted directly in the brain through holes in the skull and connected to a transmitter by wires.
‘When epileptics have a seizure, a particular part of the brain starts firing in a way that is abnormal,’ said Pedro Irazoqui, an assistant professor of biomedical engineering. ‘Being able to record signals from several parts of the brain at the same time enables you to product when a seizure is about to start, and then you can take steps to prevent it.’
The scientists are also developing an external receiver that will pick up data from the implanted transmitter.
According to Irazoqui, the transmitter consumes 8.8 milliwatts, one-third as much power as other implantable transmitters, while transmitting 10 times more data. It is also able to collect data specifically related to epileptic seizures from 1,000 locations in the brain. The signals are amplified, digitised and then transmitted to the external receiver
Existing implantable devices that are being clinically tested can only record epilepsy data from eight channels.
‘We are planning on doing human testing in two years,’ Irazoqui said. ‘Epilepsy affects about one percent of the global population, and of that one per cent, 30 per cent don’t respond to any drugs. There is no cure or treatment for those 30 percent.’
The researchers have also tested the ability of the transmitter to send signals through tissue.
‘We looked at the equivalent of the amount of skin that you have on your scalp, which is about two or three millimetres,’ Irazoqui said. ‘We have demonstrated that the transmitter does penetrate the thickness of tissue that would be required for this application.’
Developments of the technology could include a chemical, known as a neurotransmitter, being delivered directly to the area of the brain where a seizure is starting as soon as the device predicts the onset of a fit.
Jenna Rickus, an assistant professor of biomedical engineering, has developed a ‘living electrode’ coated with specially engineered neurons consisting of living tissue that, when stimulated with a microchip, releases the chemical.
The scientists have also managed to demonstrate that the electrical current can cause the neurons to release specific quantities of neurotransmitter.
‘By using an engineered cell to release a neurotransmitter, we have a drug pump, in essence, that automatically refills itself and that only impacts the part of the brain where the living electrode is implanted: the epileptic focus,’ Irazoqui said. ‘So you are not going to get the side effects that you get by washing the entire body in a particular pharmaceutical.’
The researchers have also developed a sensor to be implanted in the eye to monitor glaucoma by measuring pressure inside the eye.
Glaucoma is a disease that causes blindness from a build-up of fluid pressure inside the eye, killing fibres in the optic nerve. If the pressure is high, surgery or medication can be prescribed to treat it.
‘The problem is that your interocular pressure spikes over hours, sometimes minutes,’ said Irazoqui. ‘So you can be fine today and fine in six months and spend three months in the middle where it’s very high, killing your optic nerve. What you really need to do is check it often, every couple of minutes, but you can’t go to the doctor every couple of minutes for the rest or your life. So what you need is a device that measures your eye pressure continuously.’
The pressure sensor, which is placed between two layers of tissue in the eye, measures the interocular pressure and like the epilepsy device, it can transmit data to an external receiver to constantly monitor the pressure. Irazoqui also said that the device runs on a power of nanowatts.
Animal testing is scheduled to take place in December, and human trials will take place within 18 months.