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Optical tweezers for ultra-sensitive blood tests

U.S. researchers have developed a highly sensitive technique to detect, for example, viruses in blood samples. Patented by the National Institute of Standards and Technology (NIST), it relies on optical tweezers created by a laser.
The use of lasers in biology and medicine is not new and very considering to use them to reduce the risk of AIDS infection during blood transfusions. In nanotechnology as the laser plays and will play an important role. It is used already in the nanoworld to manufacture optical tweezers to trap and manipulate cells one by one.
The patented technique today by NIST is remarkably simple. The first is to make latex microspheres for the cover of an antibody given. These microspheres carry a charge and therefore suffer the influence of the electric field of laser beam. Using this you can determine the power of the laser pulse required to move a microspheres and have a measure of external forces acting on it.
One method already out of the laboratory
Then we placed on a glass slide a small sample of liquid, such as blood, containing antigens. In contact with the sample, antibodies on the latex microspheres will bind to antigens like a Velcro attachment. It only remains to measure the force required to raise the microspheres above the glass slide. Indirectly, it will be a measure of the force needed to separate antibodies and antigens and therefore how many antigens were related to glass slide (see diagram).
This assumes, of course, to have information on the types of antigens and antibodies. Once known, measuring the number of antigens associated with microspheres give indirect antigen concentration in a given volume.
The technique is very sensitive because it can detect concentrations femtomolaires, ie the presence of an antigen to a billion million molecules of water! The company Haemonetics, which provides equipment to blood banks not doing is not wrong and has signed agreements with NIST to use this technology.