Optical probes for biomolecule detection.

Optical probes for biomolecule detection

A physician of the near future might draw a few drops of blood from the fingertip of a patient suffering from some bacterial or viral infection. The physician then might spread the sample onto a disposable, antibody-coated test strip and wait a few minutes to make sure the antibodies grab as many antigen molecules as they can. After rinsing away the rest of the sample, the physician, still in the office, would place the strip into a $500, shoebox-sized optical scanner that would shine light onto the strip and monitor the angle and intensity of the reflections. If the scanner's readout was consistent with the patient's symptoms, the physician might come to an immediate diagnostic conclusion.

Existing immunodiagnostic techniques often involve sophisticated instrumentation and methods, expensive chemicals and highly trained personnel. Now, the Ares-Sorono Group, a pharmaceutical and diagnostic company based in Boston and Switzerland, is developing a new, inexpensive diagnostic technology that physicians can use in their own offices. Scenarios like the one above could be possible by 1990, says Erol Caglarcan, a spokesman for Ares-Sorono, which is developing the technique in collaboration with PA Technology, a British scientific consulting firm.

Company scientists are using a physical phenomenon called surface plasmon resonance for directly detecting specific infectious viruses and bacteria in samples of blood or other body fluids. Plastic or glass strips are coated with a thin film of silver followed by a layer of monoclonal antibodies that recognize only specific infectious agents. When light is beamed onto the test strip's surface, the silver's electrons undergo a collective motion known as a surface plasmon.

Since this motion draws off energy from the light beam, reflections from the surface are significantly lower in intensity. If present, antigens--the infectious agents--bind to the antibodies, and the properties of the test strip surface are altered, resulting in changes in reflection angle and intensity. From these differences, Caglarcan says doctors will be able to determine what infectious agents are present in patients.