Frontier: Eye drops explored as alternative to brain biopsy
News from the frontier

by Faith Hickman Brynie

May, 2008

Many brain diseases and injuries trigger the growth of tissue in the brain. Such repair is hard to detect except by brain biopsy, which can damage healthy tissue. Now researchers at Harvard think there may be a better way: eye drops.

Philip Liu and his team designed a probe molecule that contains nanosized particles of iron oxide. They linked the particles to a short DNA strand; the DNA matched a gene sequence found only in certain types of cells in repair tissue.

In its healthy state, the blood-brain barrier, a tight layer of cells and tissue that separates the brain from the rest of the body, would block such a molecule from entering the brain. But many injuries and diseases disrupt the barrier, so Liu’s team reasoned that the probe might travel from the eye to the brain when the barrier is not intact.

In mice with “leaky” barriers, Liu delivered the probe via eye drops. Using magnetic resonance imaging, or MRI, his team found tissue growth in the brain. The DNA part of the probe latched onto growing cells, and the MRI detected the probe’s iron particles.

Liu thinks such probes might be used to monitor brain repair after a stroke or to locate brain tumors. “The probes might also disclose the thinning of blood-vessel walls in the brain that occurs in Alzheimer’s disease,” he adds.

The research was published in the April FASEB Journal, the journal of the Federation of American Societies for
Experimental Biology.