15 July 2008

Nanowire sensors for continuous monitoring of protein markers

Doctors often evaluate the levels of certain blood proteins to detect organ malfunctions and other problems in seriously ill or injured patients. Specialists of the newly created Vista Therapeutics company, based in Santa Fe (New Mexico), hope to improve the effectiveness of treatment of such patients with the help of sensitive devices for continuous monitoring of blood biomarkers. Instead of daily blood sampling for analysis, the nanosensors developed by the company will allow for a long time continuously (or every 5-10 minutes) to read changes in the concentrations of marker proteins.

According to Spencer Farr, executive director of Vista Therapeutics, the first practical application of the new technology will be the observation of patients whose condition may change dramatically, primarily those in the intensive care unit due to a heart attack or traumatic injuries as a result of a car accident.

To create new detectors, the company licensed nanowire sensor technologies developed by Harvard University chemist Charles Lieber. Silicon nanowire – a semiconductor with a thickness of no more than 2 nm – provides extreme sensitivity even when analyzing unprepared samples, such as whole blood. Even if only one protein molecule binds to one of the antibodies attached to the nanowire, the electrical conductivity of the nanowire changes. Hundreds of nanowires designed to detect different molecules in a single sample can be placed on small inexpensive chips.

The changes occurring during monitoring can be observed continuously as the molecules bind and cleave, which makes it possible to register even the most insignificant trends without the need for multiple blood sampling.
The method of enzyme immunoassay (ELISA) traditionally used to detect proteins is quite sensitive, but it takes at least an hour and a half to carry it out. The authors note that ELISA is an indispensable tool for single measurements of protein levels, but is inconvenient for tracking changes that occur over hours, not days or weeks.

The high sensitivity of nanowire detectors opens up the possibility of using new biomarkers. The levels of some traditionally analyzed markers, such as prostate-specific antigen (for detecting prostate cancer) and C-reactive protein (a sign of heart failure and many other pathological processes), change over days and weeks, so their monitoring is also possible with the help of ELISA. The new sensors will allow doctors to observe changes in the levels of other proteins that occur in a much shorter time and are not recorded by modern methods.

The first models of nanosensors will be designed for use in combination with intravenous catheters, and later specialists hope to develop implantable chips for patients with chronic diseases such as diabetes. In addition, they believe that, due to the low cost and high sensitivity, nanowire chips can also be used to make tests for detecting malignant tumors for home use.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of TechnologyReview


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