by
Kathy Mahdoubi, Senior Correspondent | October 28, 2009
Nano predators paint the brain and poke holes in tumor cells
Meanwhile, at the University of Washington, researchers are developing cancer-targeting imaging agents using a peptide isolated from the venom of the deathstalker scorpion. The researchers have taken that chlorotoxin and conjugated it with fluorescent nanoparticles that can "paint" tumors in MRI and optical imaging. This agent is specifically engineered for brain cancer tumors and is encapsulated in a biodegradable nanomaterial that allows, for the first time, a nanoimaging agent to pass through the near-impenetrable blood-brain barrier. This agent has the potential to improve current imaging resolutions by a factor of 10 or more, says Dr. Miqin Zhang, professor and nanomedicine researcher at the university.
The nanoimaging agent's cancer targeting ability comes from the chlorotoxin's natural attraction to the expression of matrix metalloproteinase, or MMP2.
"The majority of tumor cells express this MMP2, especially brain tumor cells," says Dr. Zhang. "Chlorotoxin binds to the MMP2 complex. Unlike antibodies that specifically target one kind of cancer, chlorotoxin can see many types of cancer. This is very important, because the brain can have many types of tumors. The chlorotoxin can also inhibit cell invasion, so it has a therapeutic function. Brain tumors are quite invasive and metastasize quickly. If we inject this chlorotoxin we may be able to stop invasion."
High-resolution transmission
electron microscopy of bamboo
fungus coated with nanomaterials
(Image courtesy of the
University of Alberta)
The nanoparticle's passage through the blood-brain barrier is made possible by a combination of the particle's diminutive size, chlorotoxin's already proven ability to cross the barrier and with the use of nanomaterials like chitosan, a natural polymer present in crab shells, which helps ease the journey due to its slightly positive charge. Polyethylene glycol makes the whole thing more stable and increases blood circulation time. Typically, molecule-based agents leave the body within minutes, but nanoimaging agents like this one can circulate for hours, says Zhang. The entire nanoparticle is completely biocompatible and biodegradable.
