Joint solution

A 'lab in a shoebox' that quickly diagnoses the cause of arthritis in each sufferer will allow treatment of the condition to be targeted more accurately, it is claimed.

The portable instrument —developed by researchers at the Fraunhofer Institute for Reliability and Microintegration (IZM) in Munich, in collaboration with German biotechnology company Mikrogen — can supply diagnostic information from a single drop of blood within two hours.

The device will replace weeks of laboratory investigations, during which a patient might unwittingly be given the wrong treatment, according to its creators.

Arthritis can be triggered by any of at least eight pathogens. It is not always easy to find out which pathogen, if any, is responsible in each case, because infection may have begun many years previously.

IZM's Karl Neumeier began to develop a better instrument in 2001, turning to microtechnology to build something that would fit into any doctor's surgery and supply a diagnosis in one day, allowing the best medication to be prescribed at the earliest opportunity.

The heart of the system is a biochip — a black thumbnail-size plastic wafer — embedded in a disposable, injection-moulded cartridge the size of a credit card.

When half a millilitre of blood is placed on the cartridge, it flows through microchannels and fluid distributors to 500-micrometer diameter dots of antigens — substances that react with antibodies within the blood. This reaction is made visible with more antibodies that have been tagged with fluorescent dyes.

Signals from the tagged antibodies are then captured by a fluorescence reader that includes software for data analysis and interpretation. 'Our test system quickly indicates whether the patient has ever had any contact with one of these antigens,' said Neumeier.

The blood serum contains all the antibodies that the person's immune system has ever produced. If an antibody from the blood finds its 'own' antigen on the chip and reacts accordingly, the device identifies the respective antigen. If the test fails to produce a response, the cause is not an infection at all, but degeneration of the joint.

The system can process up to five cartridges from different patients at the same time. Processing takes up to two hours and the instrument takes another five minutes to generate a read-out.

'It was developed from scratch,' said Neumeier. 'Most biochip systems are based on silicon — ours is based on plastic.'

The tiny antigen dots were applied to the surface of IZM's biochip using piezoelectric printing techniques, that allows for a dot density of up to 100 per sq cm.

Neumeier is bullish about the commercial prospects for the 10kg unit. 'The system has met with considerable interest, and we have already received inquiries from would-be users,' he said.

Once Mikrogen has completed all the studies required by German medical products legislation it will start delivering the devices to doctors' practices in 2009, although a price has yet to be fixed.

If Neumeier's predictions are correct, the instrument will help make life better for arthritis sufferers with inflamed and swollen joints by helping doctors to prescribe the appropriate medication.

The same technology will also be integrated into a second biochip cartridge being developed to analyse the antibodies in the blood of pregnant women, to quickly detect any infections that may be a cause for concern.

It will be compatible with the same processor and fluorescence reader as used by the arthritis biochip.

Neumeier is working on this biochip and hopes it will also be available to doctors in 2009. 'The simultaneous detection of the [blood serum] response against up to 100 recombinant and other antigens is the main hurdle,' he said.

Biochip development has accelerated worldwide as biochemists have borrowed fabrication technologies from the semiconductor industry. It has been largely driven by the pharmaceutical sector's need for quicker and cheaper ways to test new drugs.

According to the Worldwide Biochip & Equipment Market report published by Fuji-Keizai, the technology is now sufficiently robust for pharmaceutical companies to take substantial financial stakes in biochip companies. The global biochip market is predicted to grow by more than 12 per cent and be worth about £2bn by 2010.