Biological Sensors Devised by Institute Scientists


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Dr. Itzhak Yuli. Detecting drugs or explosives


A novel design for highly sensitive biosensors -- microelectronic devices that take advantage of biological detection and amplification mechanisms -- has been developed by Prof. Carlos Gitler and Dr. Itzhak Yuli of the Institute's Department of Membrane Research and Biophysics. Such biosensors may some day be used instead of animals to detect drugs and explosives, or to test pharmaceuticals and cosmetics. They may also be integrated into portable on-line monitors to greatly improve the sensitivity of standard chemical analysis performed in medical diagnostics, and eventually may be inserted into the human body to continuously monitor minute concentrations of chemicals relevant to various diseases.

Biological sensory systems are known to be nature's most efficient and highly selective detection devices. The environmental signals that living organisms detect through vision, smell or taste, and the internal signs involved in nerve triggering or hormonal stimuli, all produce changes in chemical states. Some of these chemical modulations activate a variety of ion channels -- proteins that by opening up create pathways for the flow of electrically charged elements through otherwise highly impermeable cell membranes.

The new biosensor design is based on an artificial biological membrane containing synthetic varieties of such ion channels, sophisticatedly attached to a gold electrode. These channels open up in response to specific chemical signals, causing modifications in the electrical conductivity of the membrane, which can be easily recorded.

The new bionic device will use a liquid crystalline phospholipid membrane that is indirectly attached to the gold electrode by "spacer arms" of detergent-like molecules. One end of these rod-like molecules blends naturally into the membrane, while the other end is modified so as to acquire a high affinity for gold. This design endows the membrane with both mechanical stability and structural flexibility, and minimizes the need to utilize an ultrasmooth electrode surface.

Sensing elements of two different types are under study. One of them involves synthetic polypeptides resembling melittin, a toxin in bee venom which spontaneously penetrates into cell membranes to form active ion channels. A second system uses genetically engineered proteins similar to natural ion channels that open upon recognizing a given substance.

Title to the patent on this biosensor design is held by Yeda Research & Development Co. Ltd., which promotes the commercial exploitation of know-how originating in the Weizmann Institute.

Prof. Gitler holds the E. Stanley Enlund Chair in Membrane Research.

Artificial membrane and ion channel