The blood-brain barrier is a group of cells that line the brain’s blood vessels, protecting vital brain structures from foreign substances. The barrier has posed enormous difficulties for researchers who want to deliver therapeutic drugs to the brain to treat tumors, infections and degenerative brain diseases such as Alzheimer’s and Parkinson’s.
The new method takes advantage of a process called transcytosis, which a cell normally uses to transport necessary molecules, such as cholesterol, into the brain. In early tests, BRNI scientists were able to use the new way to deliver a variety of test substances into the brains of rats with no ill effects.
Researchers are hopeful that this will some day be helpful to patients, according to Daniel Alkon, M.D., scientific director of BRNI.
“This may lead to a powerful new tool that clinicians can use to treat brain diseases,” Dr. Alkon said. “The blood-brain barrier provides effective protection to the brain against circulating toxins, bacteria and other harmful substances. But we need to have an effective means of delivering drugs across the barrier if we are going to offer patients better treatment options.”
The new method patented by BRNI is based primarily of low-density lipoproteins (LDLs), a class of molecules that naturally occur in the blood. To help the LDL particles reach their target, BRNI researchers have coated the particles with a natural protein known as apolipoprotein E, which helps direct the particles to receptors on the blood-brain barrier cells. These receptors then assist the particle, which can contain any drug in its central lipid core, across the barrier into the brain.
According to Alkon, previous attempts to develop carriers relied on viruses and artificial polymers, which could penetrate the barrier, but posed high levels of risk. Earlier carriers, like liposomes, were unstable, or tended to rid their cargo in unwanted places – like the liver or blood vessel linings. BRNI’s system prevents lipoproteins from abandoning their cargo until reaching the target destination, ensuring that the particles are stable in the bloodstream.
U.S. patent number 7,220,833, “Artificial Low-Density Lipoprotein Carriers for Transport of Substances Across the Blood-Brain Barrier,” was issued to BRNI for this development May 22.
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