Breaching the Brain Barrier

A new way of delivering drugs to the brain spells hope for patients of Alzheimer’s and Parkinson’s disease

Paul Ehrlich is one of the few scientists to have achieved the feat of starring in a Hollywood movie. Called the Dr Ehrlich’s Magic Bullet, the film highlights his role in the discovery of Salvarsan in 1909, the first effective drug against the scourge of syphilis. It understandably became the best known drug of its time. But this was by no means the only scientific contribution of this Nobel Prize winner. Studying the effect of staining dyes for viewing animal tissue under the microscope, he found that many of these dyes would stain every organ of an animal except the brain. A few years later, one of his students found that dyes injected straight into the cerebro-spinal fluid would indeed stain the brain, thus leading to the realisation that there was a barrier between the brain and the rest of the body that blocked the entry of some select cells while also preventing bacteria from entering this organ of utmost importance. While serving a key function in securing the brain, this barrier also posed one of the main problems in treating the organ with modern medical compounds, the entry of most of which it barred.

Now, a team from the University of Oxford working on mice has found a way of bypassing this barrier. They have used exosomes, which are used by the body naturally anyway, to transport material between cells. They fused the exosomes with particular proteins that target receptors in the brain. They then filled the exosomes with genetic material that is known to turn off a gene involved in Alzheimer’s disease. The exosomes succeeded in crossing the barrier, and caused a 60 per cent decrease in the activity of the particular gene. “These are dramatic and exciting results,” says the lead researcher, Dr Matthew Wood, “This is the first time this natural system has been exploited for drug delivery.”

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Hartosh Singh Bal