09 June 2011

Dendrimers will highlight brain cancer

The tumor detector will penetrate the blood-brain barrierChemPort based on the materials of the Royal Society of Chemistry: Across the barrier for tumour imaging

Researchers from China have developed a substance capable of passing through the blood-brain barrier, which can be used for highly sensitive detection of brain tumors. The new probe substance can be used to determine the location and size of the tumor before surgery, as well as to "navigate" during the operation to remove it.

Determining the location, size and structure of a brain tumor is extremely important for the success of a surgical operation to remove the formation. However, the contrast agents currently used in magnetic resonance imaging to localize tumors are characterized by poor specificity, are excreted from the body too quickly and, most importantly, can hardly overcome the blood-brain barrier. All this leads to the fact that the existing methods of non-invasive diagnostics miss most of the newly formed tumors and even 20-30% of old tumors.

In the research group of Kong Li from Fudan University, a molecular probe was obtained for detecting tumor cells, taking as a basis a dendrimer – a branched molecule whose circulation through the body is characterized by an optimal time period for medical diagnostics, while modifying the dendrimer backbone with two functional groups designed to solve two different tasks.

One of the groups, the angiopep–2 lipoprotein ligand, promotes the delivery of a molecular probe through the blood-brain barrier, and also recognizes lipoprotein receptors present in tumor cells in increased concentrations. The second group – fragments of compounds associated with the dendrimer, capable of significant fluorescence, contributes to the fact that researchers can obtain a high-resolution image and determine the nature of brain damage by tumor cells.

The researchers tested their molecular probe on mice in whose brains human brain tumor cell cultures were implanted, and found that the new sample has a higher recognition specificity, high sensitivity and low level of systemic toxicity compared to already known probes used for control. Lee notes that the new nanoprobe will be able to be used for non–invasive determination of the boundaries of malignant brain tumors, especially newly formed ones.

Nick Long, an expert on systems for non-invasive diagnostics from Imperial College London, notes that although the use of nanoparticles as contrast agents and probes for medical diagnostics has been quite common lately, the new system based on a modified dendrimer is interesting at least because it offers a previously untapped approach. Long believes that the possibility of chemical modification of the dendrimer for solving strictly defined tasks may lead to the use of such molecular probes in many more areas of diagnostics.

The future plans of Lee's team include increasing the biological compatibility of the dendrimer molecular probe, as well as conducting full-fledged clinical studies.

The article by Yan et al. Imaging brain tumor by dendrimer-based optical/paramagnetic nanoprobe across the blood-brain barrier is published in the online issue of the journal Chemical Communications.

Portal "Eternal youth" http://vechnayamolodost.ru09.06.2011

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