Bio-optics technologies figured prominently at the 2013 American Association for the Advancement of Science (AAAS) meeting (February 14–18, Boston, MA). For instance, Stanford University's Karl Deisseroth, who continues to pioneer precise triggering of neurons through optogenetics, delivered one of a handful of topical lectures.
Janos Kirz, scientific advisor for Lawrence Berkeley National Lab's Advanced Light Source and pioneer in soft x-ray microscopy and spectromicroscopy, described 2D and 3D x-ray chemical imaging of biological systems. He noted that optical microscopy is limited in terms of spatial resolution, and electron microscopy is limited by poor penetration of electrons and the requirement that it be performed in a vacuum-which means cells must be sliced and dehydrated. X-ray microscopy bridges the resolution gap between the optical- and electron-based approaches, and "offers the best features of both" to hit the sweet spot for chemical and elemental imaging. "Advances in x-ray sources, detectors, instrumentation, and computing power are transforming x-ray microscopy," he said, "to a widely available form of high-resolution imaging." He explained that state-of-the-art x-ray microscopes can create 3D images with elemental and/or chemical sensitivity, and even movies or stop-motion or flash images of cells and proteins in their natural hydrated state.
In perhaps no other scientific field does the adage "form follows function" hold more true than in biology, especially the biology of living cells, which is why our knowledge of cells starts with imaging, said Kirz, effectively explaining the value of another symposium, titled Innovations in Imaging: Seeing is Believing. Session organizer Amy S. Gladfelter of Dartmouth College (Hanover, NH) and the Marine Biological Laboratory (MBL; Woods Hole, MA) aimed to "help motivate the next phase of interdisciplinary approaches to advance the visualization of life, from the scale of a single molecule to the whole organism." The session brought together a panel of three physicists and three biologists to explore the leading edge of bio-microscopy. "We are beginning to understand the basis for cell organization at unprecedented spatial and temporal resolution through the creative application of fundamental physics to microscopy," said Gladfelter, whose own presentation was titled Single Molecule Imaging in Live Cells.
|A living cell (MDCK) expresses septin molecules linked to green fluorescent protein (GFP). This image was recorded with the Fluorescence LC-PolScope and shows fluorescent septin fibers in color, indicating that the fluorescence is polarized and the septin molecules are aligned in the fibers. (Image courtesy of Rudolf Oldenbourg/MBL)|
Innovations in imaging
MBL senior scientist Rudolf Oldenbourg discussed MBL's development of polarized light imaging techniques that clearly reveal the dynamics of single molecules and molecular assemblies in organelles, cells, and tissues. He explained that the polarization property of light is often overlooked because the human eye does not perceive it—and therefore, we don't intuitively understand it. "Optical phenomena based on polarization may be difficult to comprehend," Oldenbourg said, but "the polarized light microscope...makes them amenable to quantitative and analytical analysis."
Other presenters in the Innovations in Imaging symposium were Jennifer Lippincott-Swartz of the National Institutes of Health on Navigating the Dynamic Cell; Eric Betzig of the Howard Hughes Medical Institute on Imaging Three-Dimensional Dynamics in Cells and Embryos; Rainer Heintzmann of King's College, London on Structured Illumination and the Analysis of Single Molecules in Cells; and John Condeelis of the Albert Einstein College of Medicine on Imaging Single Cells in the Breast Tumor Microenvironment.
Because at the cellular level, a small number of biomolecules can induce dramatic cellular responses and lead to disease, another session, New Frontiers in Single Molecule Detection and Single Cell Analysis, showcased advances in SMD and SCA and their applications. It explored how these techniques enable detection of biomarkers for early disease diagnosis, for ultrasensitive assessment of environmental impacts, and for probing distinctive functions of individual molecules in living cells. It also described how intracellular processes have inspired device design. Symposium organizer and moderator X. Nancy Xu of Old Dominion University presented on Nanoparticle Biosensors for Mapping Single-Molecule Functions in Single Live Cells, and was joined by Robert Singer of the Albert Einstein College of Medicine talking on Following Single mRNA Molecules in Living Cells and Tissues; George Church of Harvard Medical School on In-Situ Sequencing; Linda B. McGown of Rensselaer Polytechnic Institute on Investigating Protein Capture at Aptamer-Coated Surfaces; Scott Fraser of the California Institute of Technology on Imaging the Cellular and Molecular Dynamics that Pattern Embryos, and Xiaowei Zhuang of Harvard University on Single-Molecule and Super-Resolution Imaging of Cells and Tissues.