Juli 29, 2009
Physicists at New York University (NYU), US have developed a technique to record three-dimensional movies of microscopic systems, such as biological molecules, through holographic video. The technique, developed in the laboratory of NYU Physics Professor David Grier, is comprised of two components: making and recording the images of microscopic systems and then analyzing these images. To generate and record images, the researchers created a holographic microscope. It is based on a conventional light microscope, which uses a collimated laser beam instead of on an incandescent illuminator.
When an object is placed into path of the microscope’s beam, the object scatters some of the beam’s light into a complex diffraction pattern. The scattered light overlaps with the original beam to create an interference pattern reminiscent of overlapping ripples in a pool of water. The microscope then magnifies the resulting pattern of light and dark and records it with a conventional digital video recorder. Each snapshot in the resulting video stream is a hologram of the original object. Unlike a conventional photograph, each holographic snapshot stores information about the three-dimensional structure and composition of the object that created the scattered light field. The recorded holograms appear as a pattern of concentric light and dark rings.
For analyzing the images the researchers based their work on a quantitative theory, the Lorenz-Mie theory, which maintains that the way light is scattered can reveal the size and composition of the object that is scattering it.
The application of the technique ranges from research in fundamental statistical physics to analyzing the composition of fat droplets in milk.
In the microscope, a laser beam illuminates the sample. Light scattered by the sample creates an interference pattern which is magnified and recorded. Then measurements of the particle’s position, size, and refractive index are obtained.
Juli 23, 2009
Researchers at the University of California, Berkeley, US have developed the CellScope – a new microscope that can be attached to a common mobile phone with a camera to take color images of microorganisms. The CellScope consists of compact microscope lenses fitted in a holder, which is positioned in front of the mobile phones camera. By using an off-the-shelf phone with a 3.2 megapixel camera, the researchers were able to achieve a spatial resolution of 1.2 micrometers. In this way they were able to capture bright field images of Plasmodium falciparum, the parasite that causes malaria in humans and sickle-shaped red blood cells. They were also able to take fluorescent images of Mycobacterium tuberculosis, the bacterium that causes TB in humans. The development of CellScope moves a major step forward in taking clinical microscopy out of specialized laboratories and into field settings for disease screening and diagnoses. „The same regions of the world that lack access to adequate health facilities are, paradoxically, well-served by mobile phone networks,“ said Dan Fletcher, UC Berkeley associate professor of bioengineering and head of the research team. „We can take advantage of these mobile networks to bring low-cost, easy-to-use lab equipment out to more remote settings.“
CellScope prototype configured for fluorescent imaging (taken by David Breslauer, UC Berkeley)
Juli 1, 2009
Together with his research team, Professor Vasilis Ntziachristos from the Helmholtz Zentrum Munich, Germany and the Technical University Munich, Germany developed a new technology to make light audible. The technique, called multi-spectral opto-acoustic tomography (MSOT), combines light and ultrasound to visualize fluorescent proteins that are seated several centimeters deep into living tissue.
The researchers used a genetically modified adult zebra fish which carried fluorescent pigments in its tissue. They illuminated the fish from multiple angles using flashes of laser light that are absorbed by the fluorescent pigments in the fish. The pigments absorb the light, a process that causes slight local increases of temperature, which in turn result in tiny local volume expansions. This happens very quickly and creates small shock waves. In effect, the short laser pulse gives rise to an ultrasound wave that the researchers pick up with an ultrasound microphone. To analyze the resulting acoustic patterns, a computer is attached. The computer uses specially developed mathematical formulas to evaluate and interpret the specific distortions caused by scales, muscles, bones and internal organs to generate a three-dimensional image. In the future this technology may facilitate the examination of tumors or coronary vessels in humans.
Multi-spectral opto-acoustic tomography or MSOT allows the investigation of subcellular processes in live organisms.
Juni 29, 2009
Wyatt Technology Corporation will host its 20th Annual International Light Scattering Colloquium (ILSC) on October 19-20, 2009 at the Four Seasons Biltmore Resort in Santa Barbara, California, US. The event will welcome an array of high-profile speakers including Nobel Prize winner, Professor Robert Grubbs. In conjunction with the 20th annual ILSC, Wyatt Technology will also be hosting an Eclipse Field Flow Fractionation – MALS Focus Meeting on October 21, 2009. In this meeting the application focus will be proteins, biopolymers and liposome/virus particles.
Juni 3, 2009
3D Microscopy, taking place from July 12 -16, 2009 in Interlaken, Switzerland, is an international symposium focused on 3D imaging and spectroscopy in science. The objective of this symposium is to create a forum for researchers with different expertise and scientific interests to present their knowhow and the techniques they use to answer their scientific questions. Methods using three-dimensional imaging and spectroscopy to retrieve data in volume will be discussed, whether “light”, x-rays, electrons or near field probes are used. The conference contains 3 plenary talks and 9 sessions with invited and contributed talks and poster sessions.
Session topics are:
– High resolution TEM and AFM
– 3D CLSM and light microscopy
– 3D TEM and atom probe tomography/serial sectioning
– 3D correlative microscopy
– 3D X-ray microscopy and tomography
– 3D FIB/SEM or serial sectioning (with Denk-method) blockface tomography
– 3D image analysis and simulation
– 3D scanning probe microscopy
Mai 29, 2009
The “Superresolution” research network, founded by the German Ministry of Education and Sciences, demonstrated a new widefield microscopy technology with resolutions better than 20 nanometers. The method is based on special dyes, which’s fluorescence can be optically and reversibly switched on and off in aqueous solutions. The dyes are bond to cellular structures by using a functional group. By switching the dyes on and off, the fluorescence emission is separated in time until only those dye molecules fluoresce that have enough distance to allow their localization as single molecules. After several thousand switching cycles, a total image is constructed (dSTORM – direct stochastic optical reconstruction microscopy). Involved in the project were the work groups of Prof. Dr. M. Sauer and Prof. Dr. J. Mattay (University of Bielefeld, Germany ), Prof. Dr. K.-H. Drexhage (University of Siegen, Germany), Prof. Dr. J. Enderlein (University of Goettingen, Germany), and Prof. Dr. S. Hell (Max Planck Institute of Biophysical Chemistry, Goettingen, Germany).
Cytoskeleton of a fixed cell. Left: Fluorescence image at standard conditions. Right: dSTORM image using molecular switches.
April 29, 2009
A new imaging method that could help to build more powerful microscopes and other optical devices by producing sharper images and a wider field of view has been developed by Princeton researches. The research was led by Jason Fleischer, assistant professor of electrical engineering and co-written with two graduate students Christopher Barsi and Wenjie Wan. The new method takes advantage of the unusual properties of nonlinear optical materials in which light rays mix with each other in complex ways. Thanks to the mixing of rays, information that would otherwise be lost manages to reach the detector. Therefore this picture would be rich in detail but it would also be distorted. To capture this otherwise lost visual information, the researchers used a hologram. The hologram is a special type of photograph which records „phase“ – a light property which measures the time and location of a wave peak. They also combined data from a normal camera. Then they created a simplified flow of light through a nonlinear material and developed a computer algorithm that takes the distorted image and works backwards to calculate the visual information at every point in space between the image and the object.
An object illuminated by light reflects rays in many different directions (gray arrows). Left: With a normal lens, some rays are captured and refract towards a camera while others are missed, resulting in a blurry image with a limited field of view. Right: The new method uses a nonlinear material. The original rays are altered and new rays (red) are generated. The resulting picture is scrambled, but a computer algorithm can undo the mixing and yield a sharp, wide-field image. (Image: Christopher Barsi)