Dual-mode nanoscale imaging yields new details of cellular events

To create drugs capable of targeting malignancies, scientists must first decode exactly how a cell or a group of cells communicates with other cells and reacts to a broad spectrum of complex biomolecules surrounding it. But even the most sophisticated tools currently used for studying cell communications suffer from significant deficiencies.

Typically, these tools can detect only a narrowly selected group of small molecules or, for a more sophisticated analysis, the cells must be destroyed for sample preparation. This process makes it difficult to observe complex cellular interactions as they would occur in the body.

Investigators from the Georgia Institute of Technology appear to have solved this problem with a new nanoscale probe, the Scanning Mass Spectrometry (SMS) probe, that can capture both the biochemical makeup and topography of complex biological objects in their normal environment. This research was published in the journal IEE Electronics Letters.

"At its core, disease is a disruption of normal cell signaling," said Andrei Fedorov, Ph.D., who led the team of investigators that developed the SMS. "So, if one understands the network and all signals on the most fundamental level, one would be able to control and correct them if needed. The SMS probe can help map all those complex and intricate cellular communication pathways by probing cell activities in the natural cellular environment."

The SMS probe uses a conceptually new approach to ionizing biomolecules, creating a nanoscale probe with the ability to gently pull biomolecules, such as proteins, metabolites, and peptides, precisely from a specific point on the surface of cells and tissues and ionize these biomolecules. Focusing electrodes on the SMS probe produce "dry" ions suitable for analysis. The probe then transports those ions to a mass spectrometer for identification. The probe does this dynamically, imaging the surface and mapping cellular activities and communication potentially in real time. In essence, in scanning mode, the SMS probe could create images similar to movies of cell biochemical activities with high spatial and temporal resolution.

The SMS probe can be readily integrated with the Atomic Force Microscope (AFM) or other scanning probes, and can not only image biochemical activity but also monitor changes in the cell or tissue topology during the imaging process. "The probe potentially allows us to detect complex mechano-bio-electro-chemical events underlying cell communication, all at the same time," Fedorov said.

Another group of investigators, led by Miklós Kellermayer, M.D., Ph.D., and László Grama, Ph.D., both at the University of Pécs, in Hungary, have integrated atomic force microscopy with real-time fluorescence imaging. This new instrument provides researchers with another method for simultaneously mapping physical and chemical information in molecular detail. This research was published in the Biophysical Journal.

The investigators built their new instrument by integrating an atomic force microscope with a commercially available fluorescence microscope. The researchers integrated the two instruments using lasers, coupling optical fibers and a CCD camera to align images from the two instruments. The investigators note that the equipment needed to integrate the two imaging techniques cost approximately $30,000 over the cost of the two microscopes, and that set up is relatively easy.

The work combining mass spectrometry with atomic force microscopy is detailed in a paper titled, "Scanning mass spectrometry probe for biochemical imaging." An abstract of this paper is available at the journal’s website. View abstract.

The work combining fluorescence spectroscopy and atomic force microscopy is detailed in a paper titled, "Spatially and temporally synchronized atomic force and total internal reflection fluorescence microscopy for imaging and manipulating cells and biomolecules." Investigators from the University of Heidelberg, in Germany; Supertech, Ltd., in Pécs, Hungary; and Asylum Research, in Santa Barbara, CA, also participated in this study. The full text paper is available free at the journal’s website. View paper.

http://nano.cancer.gov

22nd August 2006