Cornell maintains that his group's design makes it easy to create a wide variety of very sensitive and stable biosensors by simple switching of the doorman molcules. So far they have built chips that can detect viruses, bacteria, drugs, proteins, DNA sequences, and medically important minerals such as potassium and calcium. Cornell's tests show that the sensors can accurately measure levels of target compounds present in blood, serum and urine samples. These biosensors appear to remain stable over a wide range of temperatures. That is important, says Anthony P. F. Turner, head of the Institute of BioScience and Technology at Cranfield University in England, because "stability is a major technical problem for many applications."

Image: R. Pace/P. Cambell/AMBRI MOLECULAR LANDSCAPE depicts the working of the ICS Biosensor. Compounds of interest (green globs) link up with antigens (orange "arms") which in turn connect to sites in the underlying membrane, disrupting the flow of electricity, thereby indicating the presence of the compounds.

So is cost. Current affinity sensors cost $100,000 or more. The ICS Biosensor, Cornell claims, should be about 10,000-fold cheaper. In fact, manufacturing appears straightforward, he says: "The process is to take a gold-coated electrode and dip it into several solutions. All the layers of chemicals that make it work simply self-assemble." Cornell reckons that the chips should cost just a few dollars each once they go into mass production.

AMBRI, a subsidiary of Pacific Dunlop, is commercializing the device and expects to have the first related products ready for market around 2000. Early applications will include bedside tests for heart attack, drugs of abuse and perhaps a few common genetic mutations. Beyond that, Cornell says, it should be possible to adapt the design of the ICS Biosensor to create sensitive detectors for almost any important biological molecule.

Turner agrees that "the Cornell design, if it is verified in practice, represents a step forward. It promises increased stability of a very sensitive configuration. Being optimistic, I believe we are on the verge of a microsensor revolution which could rival the microprocessor revolution in size, scale and impact." Indeed, Turner adds enthusiastically, "micro-analytical devices could pervade our lives in the next decade or two!"

Then, a medic might take a drop of blood from our hypothetical patient and drop it into a biosensor. Within seconds, the device reveals the patient to be Rh-positive, HIV-negative and suffering not from a heart attack but from an overdose of digoxin. Information like that could save the fellow a very expensive shot of heart attack mediation. Not to mention his life.

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