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Nanotech News
Reviewing Progress on Imaging Dendrimers and Degradable Dendrimers Dendrimers are among the promising materials that cancer researchers are using to develop nanoparticles for detecting and treating tumors (click here for additional stories on dendrimers in cancer research). Two reviews published this month in the journal Molecular Pharmaceutics highlight the progress investigators are making in developing clinically useful products. Martin Brechbiel, Ph.D., and his colleagues at the National Cancer Institute’s Center for Cancer Research reviewed the use of PAMAM dendrimers to form nanoscale contrast agents to improve tumor imaging. These dendrimers are well suited for imaging applications because they can be targeted to tumors and carry large numbers of paramagnetic metal atoms that are then readily visible using standard clinical MRI scanners. Importantly, these metal ions, which are often toxic in free form, remain attached to the dendrimers. The authors also note that the size and chemical composition of dendrimers can be altered to fine-tune their pharmacokinetic behavior. They believe that it will soon be possible to predict how various modifications to a dendrimer’s structure will affect its targeting ability, pharmacokinetic behavior, and imaging properties. Future studies on the incorporation of multiple imaging agents within a single dendrimer should also boost the usefulness of these nanoparticles. In the second paper, Dominic McGrath, Ph.D., of the University of Arizona, reviewed dendrimer disassembly, a new concept in nanotechnology. The operative principle that he discussed is that dendrimers can be constructed to fall apart in response to a single triggering event, such as an enzymatic reaction of a signaling event. As they fall apart, the dendrimers would release any molecules they were carrying. The review discusses methods that Dr. McGrath’s group and other teams have developed to start the chemical cascades that will cause a dendrimer to disintegrate after the signaling event. Researchers have already used these methods to create dendrimers that will release the anticancer drugs doxorubicin, camptothecin, or both. This study showed that releasing both drugs simultaneously within a cell was 50 times more toxic to cultured cancer cells than was administering each drug individually from separate nanoparticles. Research with disintegrating dendrimers is now focused on developing new chemical techniques for triggering dendrimer degradation on command. The review covering dendrimers as imaging agents appeared in a paper titled, “PAMAM dendrimer based macromolecules as Improved Contrast Agents.” An abstract of the paper is available through PubMed. The review covering degradable dendrimers appeared in a paper titled, “Dendrimer disassembly as a new paradigm for the application of dendritic structures.” An abstract of the paper is available through PubMed. |
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