News | The CEA
Weighing and Identifying Molecules One at a Time
30 August 2012 | Measurement is done with nanocomponents and can be used to identify particles and molecules in real time. There are numerous potential applications, particularly in medical diagnostics.
The new instrument developed by researchers from Caltech and CEA-Leti uses nanocomponents called nanoelectromechanical systems (NEMS) that can detect particles. The component, several millionths of a meter in size, consists of a resonating silicon “bridge”. When a particle or molecule lands on the bridge, its mass changes the oscillating frequency in a way that reveals how much the particle weighs. To determine its mass exactly, its location on the bridge must also be known since this affects oscillation frequency. The researchers demonstrated that analysis of changes in oscillation frequency were sufficient to determine the location and mass of a particle. “As each particle comes in, we can measure its mass,” explains Michael Roukes, Caltech professor. “Nobody’s ever done this before.”The researchers demonstrated how their new tool works by weighing a molecule called immunoglobulin M (IgM), an antibody produced by immune cells in the blood. By weighing the various masses of molecules with the detector, the researchers were able to count and identify the various types of IgM in the sample. Not only was this the first time a biological molecule was weighed using a nanomechanical device, but the demonstration also served as a direct step toward biomedical applications. Future instruments could be used to monitor a patient’s immune system or even diagnose immunological diseases. For example, a certain ratio of IgM molecules is a signature of a type of cancer called Waldenström macroglobulinemia. In the more distant future, the new instrument could give biologists a view into the molecular machinery of a cell. Mass spectrometry is usually used, but this method does not work for more massive particles like proteins or viruses. This technique can thus supplement spectrometry by helping medical doctors to diagnose certain diseases and providing biologists with new tools to study viruses and bacteria and probe the molecular machinery of cells. “By using processes derived from microelectronics, we’re well on our way to creating such instruments,” explains Hughes Metras of CEA-Leti, assigned to Caltech as part of the cooperative effort. “The new technology could for example be used in commercial mass spectrometry instruments to increase measurement range.”“This result demonstrates how the Leti-Caltech Alliance, initiated in 2006, creates a favorable environment to carry out innovative experiments with state-of-the-art, mass-produced devices,” states Laurent Malier, director of CEA-Leti. The result of manufacturing techniques used in microelectronics, it may be possible to produce components with this technology on a large-scale. “These devices,” he says, “will enable commercial applications, thanks to cost advantage and process repeatability.”