Medical Device Daily National Editor
It may be a flat world these days in terms of business, finance, art and many other areas, but 2-D flatness seems to be rather pretty passé for laboratory researchers these days.
Medical Device Daily last month reported on a system for spinning cells to develop microscopic images from all sides, putting them together in a computed tomography-style strategy to create 3-D views (MDD, "3-D microscope may close image gap with CT hardware 'spin''; Feb. 19, 2008), such images of cells and other materials offering much more information for analysis and treatment.
Now, a team of scientists at Vanderbilt University (Nashville, Tennessee) report their own version of this multi-dimensional approach for imaging, this time using a "periscope" strategy to view cells and other microscopic materials from all sides.
They say they have invented the world's smallest version of a periscope, in microscope form, thus enabling them to peek around the corners of cells and other micro-organisms, to see them from all sides, all at once.
"With an off-the-shelf laboratory microscope you only see cells from one side, the top," says team member Chris Janetopoulos, assistant professor of biological sciences at Vanderbilt.
With the new microscope, "Not only can we see the tops of cells, we can view their sides as well something biologists almost never see."
The new strategy could have "classical applications, the majority as a lab tool," Janetopoulos told Medical Device Daily.
The devices accomplishing this have been named "mirrored pyramidal wells" by the researchers. And Janetopoulos says that the coatings on the sides of the wells essentially turn them into mirrors and thus provide the around-the-corner views of the materials examined.
As the name suggests, these wells consist of pyramidal-shaped cavities. Made of silicon, the interior surfaces of the wells are coated with a layer of gold, platinum or other materials that make them highly reflective. They are, appropriately, microscopic in dimension 50 microns to 200 microns in diameter the range of sizes enabling their use in viewing different-sized objects.
Best of all, these wells can be used with standard optical microscopes, according to Kevin Seale, assistant professor of the practice of biomedical engineering. And he emphasizes another low-cost characteristic of the system.
He told MDD that the mirrored wells can be made for only about $3 each, and are usable several more times, "unlike other, more complex methods for 3-D microscopy."
Seale credits fellow scientist Ron Reiserer with much of the design and basic fabrication of the pyramidal wells.
Reiserer is lab manager at the Vanderbilt Institute for Integrative Biosystems Research and Education (IBRE), which specializes in making micro and miniature systems for use in a variety of lab settings, or assisting others in making such devices.
Reiserer says the reflective microwells "could easily become as ubiquitous as the microscope slide and could replace more expensive methods currently used to position individual cells."
Seale agrees with Janetopoulos that the first versions of the microscope will likely be used most often for research purposes but that future versions could find their way into small labs and physician offices.
"A lot of things we do [in the IBRE lab] are aimed at the doctor's office or the point of care," he says. "We've always been interested in devices for treating HIV in Africa by using microfluidic devices that can work with no power, so they can run in places where no electricity and still do complex measurements," he says, as one example.
He says that the Vanderbilt researchers aren't the first group to make these mirrored wells, but the first to use it in this way.
Members of the team researched various applications for the mirrored wells and learned that in 2006, a group of scientists in England created pyramidal micromirrors and applied them to trapping atoms. And last spring researchers at the National Institute of Standards and Technology used similar structures to track nanoparticles.
But they found no applications specifically involving microscopy.
"We had the idea to look at cells with a mirror," Seale says, "and thought somebody would have done it before."
Finding they hadn't, "We were kind of surprised by that," he adds.
So far, the researchers have used the mirrored wells to examine how protozoa swim and cells divide.
"The method is particularly well suited for studying dynamic processes within cells because it can follow them in three dimensions," Janetopoulos says.
Vanderbilt has applied for a patent on the use of the pyramidal mirrored wells for simultaneous, multi-vantage-point imaging.
Researchers in his lab have used the wells to track the 3-D position of the centrosome the specialized region of a cell next to the nucleus that is the assembly point where the microscopic polymer tubes that serve as part of the cell's cytoskeleton are assembled before cell division and broken down afterward.
The mirrored pyramidal wells provide a high resolution, multi-vantage-point form of microscopy that also makes it easier for researchers to measure a number of important cell properties, according to Janetopoulos.
He says the micropyramid wells also have a major advantage for single molecule studies. Optical noise is a constant problem when working at the low light levels involved. Being able to pinpoint actual light sources in two or three dimensions allows the researchers to reject spurious signals, they say.
This should be useful in quantitative fluorescence or bioluminescence studies: Cells can be genetically modified to glow in the dark to provide a measure of cellular metabolic activity or the expression of a specific gene.
The research was funded in part by a grant from the U.S. Air Force Office of Scientific Research.
Other examples of the work done with the pyrimidal wells by students at IBRE include the measurement of the volume of individual yeast cells with unprecedented accuracy. These students also plan to create mirrored microchannels to measure how cells are deformed under stress induced by fluid flowing through hair-width channels in order to determine how fluid flow affects cell behavior and attachment.