Researchers at the University of Notre Dame have discovered a way to make influenza visible to the naked eye, according to a new study. By engineering dye molecules to target a specific enzyme of the virus, the team was able to develop a test kit that emitted fluorescent light when illumina ... more
A molecular shield for near-infrared fluorescent dyes
Stable and Functional Dyes for Near-Infrared Fluorescence Imaging of Living Subjects
Scientists can monitor biomolecular processes in live tissue by noninvasive optical methods, such as fluorescence imaging. However, the fluorescent dyes used for that purpose are often rather unstable, and photobleaching, lack of specificity, and poor pharmacokinetics are recurrent issues. US scientists have developed a molecular shield that stabilizes near-infrared fluorescent dyes and enhances their functionality. Their synthesis and characterization are reported in the journal Angewandte Chemie.
Fluorescence bioimaging often uses the near-infrared light region because this radiation can efficiently penetrate human tissue. Fluorescent dyes designed for this purpose usually have a flat, symmetrical molecular architecture, which favors absorption of near-infrared light, but the dyes also need to be water soluble and carry functional groups for conjugating with targeting biomolecules, for example, antibodies or tumor-binding peptides. A member of this class of fluorescent dyes, called heptamethine cyanines, or Cy7, is currently under investigation in surgical applications.
However, the Cy7 molecules have their drawbacks. Their light-absorbing chromophore is vulnerable to oxygen radicals, which leads to bleaching. In addition, the flat rigid molecules may aggregate and interact nonspecifically with other biomolecules, which slows down their clearance from the body.
To tackle these issues, Bradley D. Smith and his group at the University of Notre Dame, USA, improved the chemical structure of the dye. To protect the heptamethine chromophore from oxygen attack, they introduced a voluminous and smart shield. They attached a bulky aromatic group on top of the central part of the chromophore and furnished this top group with long shielding arms projecting over both faces of the chromophore, like a bird covering its nest with its wings.
The resulting dye, which the scientists call “sterically shielded heptamethine cyanine dye” or s775z, was water soluble and provided stable fluorescence. The shielded architecture prevented aggregation and photobleaching, the authors reported. The dye was exceptionally stable against chemical degradation and could be stored “indefinitely” in a common refrigerator, the authors wrote.
They also performed imaging studies in live mice and found that s775z, in contrast to all other studied dyes, did not accumulate in the blood clearance organs, but was washed out of the body quickly. Moreover, a cancer-targeted version of s775z accumulated at a high level in tumors and could be visualized by fluorescence imaging of the live mice.
The authors suggest that the new s775z dye will be useful for a wide range of biomedical imaging applications. They point out that the change from a flat molecule to a three-dimensional shielding architecture was the key to make this class of near-infrared fluorescence dyes more stable and efficient.
- fluorescence imaging
- fluorescent dyes
They are the chemicals that made consumers think twice about using nonstick cookware. New research shows scientists have developed a method to track perfluorinated alkyl substances (PFAS) in the body. PFAS are potentially toxic chemicals found in stain-resistant products, nonstick cookware, ... more
Biopsies are a gold standard for definitively diagnosing diseases like cancer. Usually, doctors can only take two-dimensional snapshots of the tissue, and they're limited in their ability to measure the protein levels that might better explain a diagnosis. But now, researchers have develope ... more
In the treatment of tumors, microenvironment plays an important role. It often contains immune cells that are so changed that they promote tumor growth. In the journal Angewandte Chemie, scientists have introduced a method by which cell samples from tumors and their surroundings can rapidly ... more
A good indicator of dysregulation in live cells is a change in their RNA expression. MicroRNA (miRNA), a special type of RNA, is considered a biomarker for carcinogenic cells. A team of scientists from China has found a way to amplify miRNA in live tumor cells for bioimaging. As they report ... more
The folding state of the proteins in live cells often reflect the cell’s general health. Australian scientists have developed a molecular probe that senses the state of the proteome—the entire set of the proteins—by measuring the polarity of the protein environment. The fluorescence signal ... more
- 1New Indication of a Link Between Alzheimer’s and Diabetes
- 2Click... Resistant bacteria caught in the act!
- 3Nanosafety research without animal experiments
- 4The relationship of proteins
- 5DKSH extends partnership with Bruker in China
- 6Detecting antibodies with glowing proteins, thread and a smartphone
- 7High-end Microscopy Refined
- 8Developing new techniques to improve atomic force microscopy
- 9RNA structures by the thousands
- 10Could the blood of COVID-19 patients be used to predict disease progression?