Quantum dots outline brain tumors for surgical removal

Although surgical removal of a tumor can be the most effective way of treating brain cancer, neurosurgeons are often faced with the dilemma of determining the exact border between a tumor and the healthy tissue that surrounds it.

Now, a team of investigators at the Cleveland Clinic Foundation has found that quantum dots, when injected into animals with brain tumors, accumulate within the outer regions of those tumors. The quantum dots are readily visible when irradiated with light, identifying the outline of the tumor.

Reporting its work in the journal Neurosurgery, a research team headed by Stephen Toms, M.D., M.P.H., found that when relatively large doses of quantum dots were injected into tumor-bearing mice, the fluorescent nanocrystals accumulated within immune system cells known as macrophages. These cells can cross the blood-brain barrier and can be seen surrounding glioma cells. When irradiated with blue or ultraviolet light, the quantum dots emit a deep red fluorescence. The researchers detected the emitted light using a digital camera, optical spectroscopy devices, or dark-field fluorescence microscope.

Toms and his colleagues found that at doses of 3.4 nanomoles of quantum dots were visible only in the liver, spleen, and lymph nodes. However, injections of 17-nanomoles produced bright fluorescence in the brain of animals with gliomas. In some instances, the researchers also were able to detect metastatic lesions. Careful examination of the brain and other tissues revealed no evidence of inflammation or toxicity from the 17-nanomole injection. The investigators also found that when they injected the high dose of quantum dots into healthy animals, none of the nanocrystals were visible in the brain.

This work is detailed in the paper "Quantum dots are phagocytized by macrophages and colocalize with experimental gliomas." An abstract of this paper is available through PubMed. View abstract.



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