Doctor on a chip

Imperial College London spin-out

has developed a hand-held device that could bring low-cost diagnostics for cardiac and other conditions into the GP's consulting room or the home.

The patented system combines microfluidic lab-on-a-chip technology with light-emitting polymers (LEPs) and photodetectors to carry out a battery of medical tests simultaneously. The chip incorporates up to 10 channels, allowing the level of multiple analytes to be measured simultaneously alongside internal controls and reference samples. It does this by measuring absorbance, fluorescence, chemiluminescence and phosphorescence.

Ian Campbell, Molecular Vision's chief executive, said: 'Essentially we have an organic polymer that can be deposited on both the top and bottom sides of the microfluidics. The top polymer acts as a light-emitting diode, so when a current in the slide passes through the polymer it lights up. The polymer at the bottom acts as a photon receiver and translates the signal from light to amps. The amount of signal it receives is proportional to the amount of active material in the sample, which can then be displayed on a readout.'

Results are output within minutes and can be displayed on a LCD screen on the device, or via a PDA, mobile phone or home computer. Each could also be used to power the device, which can also run on a small internal 'button' battery.

The sample body fluid will be mixed with reagents through the microfluidic network. Sample pre-treatment, chemical reactions, analytical separations and detection are all carried out on a single chip. The system is low risk as it uses established assay technology and reagents.

Though microfluidic lab-on-a-chip assays are not new, current approaches are usually high- cost bench-top laboratory analysers or disposable kits that only test for a single analyte. Campbell claimed the new method was a significant improvement over existing methods.

'We're able to deposit the polymers in such a fashion that you can put different light sources down to measure different assay analytes,' he said.

'For example, we can combine fluorescent chemiluminescence and absorbance measurements on the one device because we're able to put down light sources of different wavelengths. So instead of adopting a single reader and modifying the assay to suit it, you can configure the reader to the assay you want to carry out.'

One key application would be testing for cardiac indicators in patients admitted to hospital for chest pain. About 30 per cent of admissions to emergency departments are for chest pain, but only 10 per cent of these turn out to be indicative of a cardiac complaint.

Key cardiac markers are Troponin I, myglobin and creatine kinase. In traditional testing, only one marker can be tested for at a time, so a battery of tests could take about four hours. Using the device, two or more tests can be carried out at a time at the point of care, whether in an ambulance, at a hospital bedside or in an accident and emergency department. Results can be displayed within minutes, diagnosing or ruling out a suspected myocardial infarct, potentially saving money, hospital beds and lives.

The lab-on-a-chip device could even help control or reduce the spread of sexually transmitted infection (STI) by providing point of care diagnostics and rapid, private results.

Many STI sufferers are too embarrassed to attend a genito-urinary medicine clinic. By providing multiple tests at once with results available within five minutes, there would be no waiting around at a clinic or repeat visits for results and treatment.

A mobile phone could be used to power the device and the results could be texted or emailed to the client and clinic. Eventually, patients could carry out tests in the privacy of their own home with an over-the-counter disposable version of the test.

Home versions of the equipment, which is the size of a small mobile phone, could also provide ongoing monitoring of chronic conditions. This could include blood sugar levels in diabetes sufferers, creatinine and albumin testing for kidney failure or warfarin levels for thrombosis prevention.

Campbell said that clinical trials would begin toward the end of 2008 or beginning of 2009, initially through professional healthcare clinics, with a view to eventually rolling out over the counter versions.

Berenice Baker