Radiolabeled nanoparticles boost PET-CT combination imaging

In an attempt to decrease the amount of cancer-targeting nanoparticle needed to image tumors, a team of investigators at the Massachusetts General Hospital and Harvard Medical School has developed a simple method for creating iron oxide nanoparticles labeled with 18F, a radioisotope that is easily detected using positron emission tomography (PET). The result is a nanoparticle that can be imaged using PET, computerized tomography (CT), and fluorescence imaging.

A research team headed by Ralph Weissleder, M.D., Ph.D., principal investigator of the MIT-Harvard University Center for Cancer Nanotechnology Excellence, reported the results of its work in the journal Bioconjugate Chemistry.

Adding 18F to nanoparticles is a major challenge to the development of cancer probes that can be imaged using PET. Dr. Weissleder and his collaborators overcame this obstacle by using a novel chemical reaction known as "click chemistry." Click chemistry can add fluorine atoms to complex biomolecules or nanoparticles using very mild reaction conditions that do not damage biocompatible constructs. This reaction also proceeds quickly, an important consideration given that the half-life of ¹⁸F is only 110 minutes.

Initial tests with radiolabeled iron oxide nanoparticles showed that the detection limit using PET-CT imaging was about 200 times lower than is possible using magnetic resonance imaging, the standard method for detecting iron oxide nanoparticles in the body. The radiolabeled nanoparticle was easily detected using PET-CT when injected into mice. The researchers plan to add tumor-targeting molecules to this nanoparticle to tests its potential utility as a tumor-imaging agent.

This work, which was detailed in the paper "18F labeled nanoparticles for in vivo PET-CT imaging," was supported in part by the NCI Alliance for Nanotechnology in Cancer, a comprehensive initiative designed to accelerate the application of nanotechnology to the prevention, diagnosis, and treatment of cancer. An abstract of this paper is available at the journal's Web site. View abstract