Cancer diagnostics: safe nanoparticles for two-photon microscopy
A new fluorescent dye for three-dimensional visualization of cancer cells
NanoNewsNet by materials Phys.Org:
Glucosamine rings turn star-shaped fluorescent dyes into powerful probes for imaging cancer cells in three dimensions
Early diagnosis of soft tissue diseases, such as breast cancer, usually requires an invasive biopsy. A new self-organizing nanoparticle developed by Bin Liu from the Institute of Materials Research and Engineering (Institute of Materials Research and Engineering) A*STAR and her colleagues can make a biopsy a diagnostic method of the past. It significantly increases the safety of two–photon microscopy, a technology in which fluorescent probes are used to obtain three-dimensional images of cancer cell structures in living tissue.
Although two-photon microscopy provides deep access to the cell, almost without damaging it, finding suitable materials for light–emitting probes is a difficult task. So, thanks to the bright and stable fluorescence, cellular structures are perfectly "illuminated" by quantum dots from nanoscale aggregates, for example, cadmium or selenium. However, the inherent toxicity of quantum dots limits their use in biomedical research.
Therefore, in the search for less toxic paints for two-photon microscopy, Liu and her colleagues turned to conjugated organic molecules. Such small molecules, as a rule, cannot absorb enough laser light to initiate fluorescence. But scientists have managed to solve this problem: they synthesized a material known as a dendrimer, which has a star shape. Consisting of a central triphenylamine core and three "arms" of long conjugated chains, this unique geometric design provides a surface area capable of absorbing photons much better than individual molecules of fluorescent dyes do.
To ensure the biocompatibility of stellate dendrimers with cellular tissue, the researchers had to resort to a chemical trick. Using the universal ability to interact with various substances of the natural polysaccharide chitosan, they connected several rings of the amino sugar glucosamine with the "hands" of the dendrimer.
According to Liu, this process reduced the cytotoxicity of the dye and allowed it to be functionalized with ligands – folic acid molecules, the targets of which are receptors on the surface of breast cancer cells of the MCF-7 line.
Experiments have shown that in an aqueous medium, the dendritic dye self-organizes into dispersed nanoparticles and provides powerful laser-induced fluorescence.
Visualization of cancer cells incubated in a medium with such nanoparticles showed bright fluorescence in their cytoplasm (see photo).
These data suggest that a specific interaction occurs between the dendritic dye and folic acid receptors on the surface of MCF-7 cells.
The close to 100% survival rate of cells at dye concentrations used in biomedical research confirms that this strategy is a safe and promising way to expand the scope of two-photon imaging.
"We really want to move from today's two–photon imaging in vitro to its use on a living organism," Liu notes.
Portal "Eternal youth" http://vechnayamolodost.ru30.10.2012