Just one Drop of Blood…

22. June 2007

Bye bye, vein tap! In the future, a sting in the finger tip might be enough. After five seconds of analytics, the attached computer supplies the prognosis - from one drop of blood only. Whether it's the threat of a heart attack or diabetes is just around the corner - modern biosensors detect the early stages of severe diseases in seemingly healthy people.

Personalized diagnostics is the magic word biomedical physicians have to deal with more and more. The principle: Tiniest biosensors recognize treacherous proteins in the blood samples of the patient – in such small quantities, that no other method has a chance to compare in this stage. A team at the Institute for Biomedical Technology at the ETH Zürich/Switzerland shows: Those ideas, just smiled at as fantasies a few years ago, have turned into something within reach. By "controlled self-organization of gold nano-particles to nano-wires", the scientists have developed biosensors, which are absolutely unique up to now. According to the Zurich visionaries, one day these will test for pathogenic germs in tiniest blood samples.

Sure enough, the road there is weary, the ETH-Professor for bioelectronics at the Institute for biomedical technology, Janos Vörös explains in the campus newsletter. But nonetheless: The super sensors including the apparatus would not be bigger than a common i-Pod. And it would enable its owner to diagnose cancer- or hepatitis antigens in his or her blood – completely autonomous. "Up to now, such examinations were only possible in a hospital. It takes 10 milliliters of blood to make antigens detectable with specific markers for expensive spectroscopic analysis devices", Vörös explains the disadvantages of the conventional methods.

Midgets made of gold

Just now in early March, the Swiss vision caught the attention of a large part of the global science community, as an article, published in the professional magazine "Nanotechnology", introduced this until then unknown type of marker-free biosensors.

The power of the biosensor is supplied by atomic midgets made of gold, although this should not bother physicians tired of physics and chemistry anyway in their every day's routine. But for those nano-freaks out there: The actual construction of those sensors is based on semi-conductor technology.

Here tiny gold particles measured by the nanometer are applied on the actual silicon carrier so tight, that the pipsqueaks are directing themselves and become conducting wires.

It's the color, that counts

In the end, the genetic substance DNA is coupled in the carrier plate with the aid of the adhesive Neutravidin. It works as an anchor for the gold particles and as a connecting link with the antigens in the blood of the patient. The show-stopper: From a blood sample infested with germs, the special gold colloids are able to bond antigens – a different protein for each disease. Those antigens "fished out" by the biosensors finally can be verified – and allocated to the according disease. Obviously the real challenge in this procedure is the identification of the treacherous antigens. Here the biosensors have another gimmick "down the sleeve": After the adsorption of the proteins, a difference in resistance can be measured in the golden nano-wires on the carrier. But also the detection by optic methods seems to be a possibility, because precious metal colloids – i. e. the gold particles of the biosensor as well – change their typical pattern in the light spectrum after absorption of an antigen.

The strength of the biosensor certainly is its sensitivity. Even single antigens cannot hide from the allrounder of the biomedical lab – a little sensation.

What every day's work in the physician's office will look like in the end of this development is foreseeable. Measuring sticks changing color depending on the diagnosis seem to be the most probable form of personalized diagnostics. The test alone at home is coming closer. Already in 2008, Vörös and his team plan to tackle the first medical use. This diagnostics initiative is no solitary case, here in Germany the branch is counting on personalized methods as well. To recognize the molecular alarm signals of the individual patient has become a must.

The Copperfield in diagnostics

Hence Epigenomics AG, a company specializing in molecular diagnostics, presented first results on a development program about an own early detection test for intestinal cancer. Accordingly, clinical data shows, that high grade biomarkers can be found for the organ specific diagnosis of cancer in blood plasma. In addition, the data proves, that the sensitive evidence of methylized DNA of the gene Septin 9 in blood plasma reliably indicates intestinal cancer in all stages of the disease. The sensation: Septin 9 in connection with a second DNA methylizing biomarker, ALX4, even detects intestinal adenoids.

For the forthcoming ANALYTICA – the world's largest trade show for laboratory and analytics after all – the highlights 2008 are already under the spell of the diagnostic magicians. Point-of-Care analytic devices are the coming stars – used right on the spot, sound and uncomplicated in their application and use.

But for researcher Vörös, the biosensor midgets from the nano-lab, compared to the common diagnostic methods, have a decisive advantage: They could, due to their manufacturing process, prove to be extremely inexpensive. The target aimed at appears ambitious: The rapid diagnosis should not cost more than one Dollar per test for the patient.

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