It's got under my skin

"We must develop as quickly as possible technologies that make possible a direct connection between the brain and the computer, so that artificial brains contribute to human intelligence rather than opposing it."

Noted physicist Stephen Hawking in a recent interview with German Magazine Focus

n February 2002 researchers at Infineon Technologies demonstrated the potential of man-machine interface through a new semiconductor technology that would allow scientists to read electrical signals in living nerve cells. The neuro-chip, about the size of a fingernail, has 16,000 sensors that can read and record signals, with the aid of computers that would help scientists better understand how the brain works and could eventually lead to treatments for neurological diseases such as Alzheimer's. For instance, amplifiers embedded in the circuitry enable each sensor to detect and process low-voltage signals throughout the different cell layers. The data can then be transmitted to a computer and eventually transformed into a color picture for analysis. Doctors could put slices from brain nerve cells on the chip, apply drugs and see how the nerve signals and how cells react to a particular drug.

Thanks to advances in nanotechnology, microelectrical systems, molecular diagnostics and several other technologies, a new class of biosensors is now being developed to detect everything from the first signature of cancer to wearable personal health products. Imagine a remarkable little particle designed for cancer patients that contains more intelligence than the entire current system of drug delivery. Taken orally, the particle passes undisturbed through the body homes in directly on the tumor cells and releases a powerful anticancer drug that destroys just the cancerous cells-with no side effects. Besides sniffing out the barest whiffs of disease - these devices could provide far faster and easier diagnosis of complex diseases. For example, they could provide early warnings about heart attacks, whose signs can be detected in subtle changes in the mix of dozens of proteins. Alternatively, a single microchip could provide a comprehensive diagnosis from a drop of blood. In an MIT 2000 conference, the ideal product was defined as an e-nanny that would have access to real-time biometric info and that would nag one to do all the right things.

The technology behind biosensors is perfectly simple. A biosensor is a probe that integrates a biological component, such as a whole bacterium or a biological product (e.g., an enzyme or antibody) with an electronic component to yield a measurable signal. Generally a biosensor has five components: a biological sensing element, a transducer, a signal conditioner, a data processor, and a signal generator. The biological component produces a signal that is related to the concentration of a specific chemical or biological substance in complex systems. The biological sensing element or a bio molecule is usually an enzyme or an antibody. Another key part of a biosensor is the transducer, which makes use of a physical change accompanying the reaction. This may be a change in the distribution of charges causing an electrical potential to be produced as in the case. The electrical signal from the transducer is often low and superimposed upon a relatively high and noisy baseline. The signal processing involves subtracting a 'reference' baseline signal, from the sample signal, amplifying the resultant signal difference and electronically filtering out the unwanted signal noise. The analog signal produced at this stage is usually converted to a digital signal and passed to a microprocessor stage where the data is processed, converted to units and output to a display device.

Schematic diagram showing the main components of a biosensor. The biocatalyst (a) converts the substrate to product. This reaction is determined by the transducer (b) which converts it to an electrical signal. The output from the transducer is amplified (c), processed (d) and displayed (e).

Although the implications for medicine biotechnology and environment are myriad, at the moment, glucose sensing for control of diabetes is the dominant commercial application for external biosensors. According to the World Health Organisation, the market for external biosensors developed mostly for the blood sugar analysis required for treatment of diabetes is $2 billion by 2004. Gluco Watch from Sankyo Pharma and Cygnus is an example of the new generation of biosensors. It's a wrist-watch like device that uses electrical signals as opposed to needle pricks.

Implantable biosensors such as devices that can be inserted just below the skin to detect that conduct body chemistry and genetic tests still confined to the laboratory. Implantable living chips may enable the blind to see, can restore hearing to the deaf, and implants might ameliorate the effects of Parkinson's or spinal damage. However in the next five to six years the market would be flooded with these new medical microscopic devices. Findings of research firm VentureOne corroborate this. According to a recent survey conducted by the company the valuations of most venture-backed companies fell by more than 50 per cent in the first half of 2002. Valuations of startups developing medical devices, however, fell by just 2 per cent. What's even more promising is that large public companies like Johnson & Johnson, and Medtronic are still buying new companies. Medtronic, for example, recently acquired the device maker Spinal Dynamics, which develops a unique artificial cervical disc, for $270 million.

But, amidst the gee-whiz, real obstacles could thwart the promise of these devices. One major obstacle is cost. Even though some biosensors can function better than other methods, the improvement is just not great enough to justify the money spent on R&D work for developing the new technology. Biosensors are also plagued by certain specific problems that are fundamentally related to the presence of biomaterial in the biosensor. Factors that have held back biomaterials are the problems associated with sterilisation, the threat of contamination etc. Three privacy and ethical conditions could create social outrage as against stem cell research. Wendy Wolfson writing in Information Week claimed: The idea of injecting chips in humans disturbs anyone concerned about the shreds of privacy we still hold. Implantable chips are the penultimate identifiers, next to DNA, which is what makes them scary. The technology isn't there yet, but it will be. Future proposals to use chips to track prisoners, implantable devices in the military to enhance the abilities of soldiers, and cyber-implants allowing information workers to communicate with machines will make current concerns about digital privacy and medical information seem trifling."

The protests not withstanding, efforts to exploit real-time sensing capabilities of biosensors in the pharmaceutical and biotechnological industries have not ceased. Stephen Hawking may be proved wrong after all!

(With Inputs from Avinash. Avinash is a freelance writer, who has contributed to various publications.)

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