Nanotech News

October 24, 2005

Nanoparticle Spots Growing Blood Vessels Using MRI and Fluorescence Microscopy

Angiogenesis, the growth of new blood vessels, is a necessary early event for tumor growth and metastasis to occur, and experimental data suggests that imaging methods that can spot angiogenesis in action could provide a means of detecting the earliest stages of tumor formation. Earlier this year, one group of investigators reported developing targeted iron oxide nanoparticles that can spot early angiogenesis. Now, a group in the Netherlands has created a nanoparticle that targets a different marker of angiogenesis that can be seen using either magnetic resonance imaging (MRI) or fluorescence imaging.

Reporting its work in FASEB Journal, a team headed by Willem Mulder, Ph.D., of Eindhoven University of Technology, had developed a liposome containing gadolinium and rhodamine. Gadolinium acts to enhance an MRI signal, while rhodamine is a common fluorescent marker. The investigators also incorporated into the outer surface of the liposome a molecule known as RGD, which binds to the protein α_vβ₃, a highly specific marker for newly activated blood vessel cells that are just beginning to grow.

Initial in vitro experiments confirmed that this liposome bound tightly to cultured cells producing α_vβ₃ and the liposomes were visible via both MRI and fluorescence microscopy. The investigators then injected the liposomes into mice with human colon tumors. Within 35 minutes, MRI scans readily spotted the edges of the tumors, which is where new blood vessel growth would be occurring. Fluorescence imaging of the excised tumors revealed that the liposomes were indeed binding exclusively to tumor-associated blood vessels. The ability to detect tumors using MRI and then visualize them using fluorescence microscopy could help surgeons ensure that they remove all of a tumor.

This work is detailed in a paper titled, “MR molecular imaging and fluorescence microscopy for identification of activated tumor endothelium using a bimodal lipidic nanoparticle.” Researchers from Maastricht University, The Utrecht Institute for Pharmaceutical Sciences, and Delft University of Technology, all in the Netherlands, also participated in this study. This paper was posted online in advance of print publication. An abstract is available through PubMed.
View abstract.