Much can be detected in blood or urine — viral illnesses, metabolic disorders, or autoimmune diseases can be diagnosed with laboratory tests, for instance. But such examinations often take a few hours and are quite complex, which is why doctors hand the samples over to specialist laboratories.
A new analysis method was developed that is based on light diffraction on molecules on a small chip. The point of light is an effect of the interplay of hundreds of thousands of molecules in their specific arrangement. As with a hologram, the wave character of the laser light is used in a targeted manner. A stripe pattern, or “mologram” (molecular hologram) and the new diagnostic technique, or “focal molography,” work together in the analysis method.
A significant advantage of the new method is that the signal (the point of light) comes about only because of the molecules that bind specifically to the mologram — other molecules present in a sample do not produce a signal. The method is therefore substantially faster than previous analysis methods based on the key-lock principle. In the latter, other molecules present in a sample have to be washed away, which in turn slows down and complicates the diagnosis. This makes the new method ideal for measuring proteins in blood or other bodily fluids.
As with other established diagnostic procedures, the new method also uses the key-lock principle of molecular recognition; for instance, in order to determine a particular protein dissolved in the blood (the “key”), it must dock on to a suitable antibody (the “lock”). In established immunological test methods, the “key in the lock” is made visible with a second color-coded key, but this step is no longer necessary in the new process — the key in the lock can be made visible directly with a laser light.
The scientists use a chip with a specially coated surface made up of tiny dots with a specific striped pattern. The molecules in question bind to the stripes, but not to the interstices between the stripes. If a laser light is now directed along the chip’s surface, it is bent (diffracted) as a result of the special arrangement of the molecules in the pattern, and focused on to a point below the chip. A point of light becomes visible. When the scientists put samples without the molecules onto the chip, the light is not bent and no point of light is visible.
Several molograms are arranged on a small chip. In the current design, 40 molograms measure the same molecule, but in the future, it may be possible to measure 40 or more different markers simultaneously on a chip.
For more information, contact Claudia Naegeli of ETH Zurich at