Monthly Tip Sheet Research Highlights from Biomedical Optics Express - October 2011


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Angela Stark
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Monthly Tip Sheet: Research Highlights from Biomedical Optics Express - October 2011

WASHINGTON, Oct. 31—The following highlights summarize key research recently published in Biomedical Optics Express, the Optical Society's (OSA) principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in the life sciences. The journal scope encompasses theoretical modeling and simulations, technology development, and biomedical studies and clinical applications.

In this issue:

  1. Fast New Method for Mapping Blood Vessels May Aid Cancer Research
  2. Using Math and Light to Detect Misshapen Red Blood Cells
  3. UV Light Controls Antibodies, Improves Bio-Sensors


Complex network of blood vessels in the mouse brain

Complex network of blood vessels in the mouse brain imaged by knife-edge scanning microscopy. The image represents an area about 2.9 millimeters across. Biomedical Optics Express.

Reconstruction of a small section of mouse brain

Reconstruction of a small section from the previous image, showing the relative thickness of each blood vessel in the network (color-coded by thickness). The area depicted in the image is about 0.275 millimeters across. Biomedical Optics Express.




Model of a healthy red blood cell with a normal dimple

Top row: Model of a healthy red blood cell with a normal dimple. Bottom row: Model of a deflated red blood cell with an abnormal dimple. Biomedical Optics Express.




UV photon is absorbed by the antibody and the disulfide bridge is opened

One UV photon is absorbed by the antibody and the disulfide bridge is opened, thereby forming thiol groups. Their interaction with the gold surface leads to an oriented Fab region so that the upside down position (circled in the right side of the picture) is hampered and the antigen binding is more effective. Biomedical Optics Express.

1. Fast New Method for Mapping Blood Vessels May Aid Cancer Research

Like normal tissue, tumors thrive on nutrients carried to them by the blood stream. The rapid growth of new blood vessels is a hallmark of cancer, and studies have shown that preventing blood vessel growth can keep tumors from growing, too. To better understand the relationship between cancer and the vascular system, researchers would like to make detailed maps of the complete network of blood vessels in organs. Unfortunately, the current mapping process is time-consuming: using conventional methods, mapping a one-centimeter block of tissue can take months. In a paper published in the October issue of the Optical Society's (OSA) open-access journal Biomedical Optics Express, computational neuroscientists at Texas A&M University, along with collaborators at the University of Illinois and Kettering University, describe a new system, tested in mouse brain samples, that substantially reduces that time.

The method uses a technique called knife-edge scanning microscopy (KESM). First, blood vessels are filled with ink, and the whole brain sample is embedded in plastic. Next, the plastic block is placed onto an automated vertically moving stage. A diamond knife shaves a very thin slice – one micrometer or less – off the top of the block, imaging the sample line by line at the tip of the knife. Each tiny movement of the stage triggers the camera to take a picture. In this way, the researchers can get the full 3-D structure of the mouse brain's vascular network – from arteries and veins down to the smallest capillaries – in less than two days at full production speed. In the future the team plans to augment the process with fluorescence imaging, which will allow researchers to link brain structure to function.

Paper: "Fast macro-scale transmission imaging of microvascular networks using KESM," Biomedical Optics Express, Mayerich et al., Vol. 2, Issue 10, pp. 2888-2896 (2011).

2. Using math and light to detect misshapen red blood cells

Misshapen red blood cells (RBCs) are a sign of serious illnesses, such as malaria and sickle cell anemia. Until recently, the only way to assess whether a person's RBCs were the correct shape was to look at them individually under a microscope – a time-consuming process for pathologists. Now researchers from the University of Illinois at Urbana-Champaign (UIUC) have pioneered a technique that will allow doctors to ascertain the healthy shape of red blood cells in just a few seconds, by analyzing the light scattered off hundreds of cells at a time. The team reports its results in the October issue of the Optical Society's (OSA) open-access journal Biomedical Optics Express.

A healthy RBC looks like a disc with a depression – called a dimple – in the top and bottom. Stressed RBCs often have deeper dimples than healthy ones, giving the cells a deflated look; others may have shallow dimples or no dimples at all. The UIUC researchers reasoned that if they shone light on a sample of blood and analyzed the light scattering off that sample, they would get a pattern – a sort of signature produced by the way light interacts with itself in a three-dimensional space – that would be different from the pattern collected from blood containing mostly misshapen cells. But these light-cell interactions were too complicated to analyze with the usual mathematical tools.  So researchers made use of the Born approximation, a mathematical rule that can be used when the object of interest is small and transparent.

By running Fourier Transform Light Scattering (FTLS) – a method developed by the same group three years ago – on individual RBCs, the scientists found that the pattern changed significantly with the diameter and dimple width of the cells. Using this information, the UIUC team applied the Born approximation to their findings and calculated what the appropriate scattering signature for healthy cells should be. They then used this new "healthy cell signature" to identify the correct morphology of cells in a blood smear. The new technique may allow for faster, accurate blood tests that could help doctors diagnose various types of anemia, and could be especially useful in resource-poor areas of the world, the researchers say.

Paper: "Born approximation model for light scattering by red blood cells," Biomedical Optics Express, Lim et al., Vol. 2, Issue 10, pp. 2784-2791 (2011).

3. UV light controls antibodies, improves bio-sensors

From detecting pathogens in blood samples to the study of protein synthesis, Quartz Crystal Microbalance (QCM) sensors have many uses in modern biology. In this technique, antibodies anchored to gold electrodes on a piece of quartz crystal act like the "hooks" on the sticky side of a Velcro strap, grabbing molecules of interest as they pass by. The more molecule-sensing antibodies on the surface of the sensor, the more sensitive the QCM device's detection capabilities.

Unfortunately, some of the antibodies typically anchor themselves to the gold plate "hook"-side-down, rendering them useless as bio-receptors and dampening the sensor's sensitivity. Now researchers from the University of Naples "Federico II" and the Second University of Naples in Italy have found a way to increase the number of right-side-up antibodies in this well-established molecule detection process – using light. In a paper recently published in the Optical Society's open-access journal Biomedical Optics Express, the team of scientists irradiated antibodies with ultra-short pulses of ultraviolet (UV) light. The UV light is absorbed by the amino acid tryptophan, which breaks the disulfide bridges holding parts of the antibody together and causes a particular part of the amino acid cysteine, called a thiol group, to become exposed at the tail end of the antibody. Because thiol groups are more strongly attracted to the gold electrodes than other parts of the antibody, the bottom sides of these irradiated antibodies become much more likely to adhere to the gold electrodes than the "hook" ends. Using this method, the researchers were able to more than double the sensitivity of the QCM device, opening up new possibilities for research using this type of sensor, the researchers say.

Paper: "Light assisted antibody immobilization for bio-sensing," Biomedical Optics Express, Della Ventura et al., Vol. 2, Issue 11, pp. 3223-3231 (2011).

EDITOR'S NOTE: Images for each tip above are available to members of the media. Contact Angela Stark, astark@osa.org.

About Biomedical Optics Express

Biomedical Optics Express is OSA's principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in the life sciences. The journal scope encompasses theoretical modeling and simulations, technology development, and biomedical studies and clinical applications. It is published by the Optical Society and edited by Joseph A. Izatt of Duke University. Biomedical Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/BOE.

About OSA

Uniting more than 130,000 professionals from 175 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.

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