Scientists have developed a method for using nanoparticles to deliver drugs to the brain for treating neurodegenerative diseases such as Alzheimer’s and Parkinson’s. They have shown that their method works in both cultured cells and zebrafish.


The biggest hurdle in treating neurodegenerative diseases is the blood-brain barrier (BBB), a border designed to protect the brain from potentially harmful substances in the blood. Only certain things can pass through the BBB: pathogens, antibodies and large molecules are blocked, and only certain antibiotics can pass through. Glucose can cross it, but only with the help of a specific transport protein.

"The blood-brain barrier filters out harmful substances to prevent them from freely reaching the brain. But this same barrier also blocks the passage of drugs," explains pharmacologist Professor Charles Ramassamy, Chairholder of the Louise and André Charron Research Chair on Alzheimer's disease.

Usually, neurodegenerative diseases are treated by giving high doses of a drug, so that a small amount will succeed in crossing the barrier. However, this leaves a large amount in the blood, which can give rise to significant side effects.

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Researchers from the Institut national de la recherche scientifique in Canada have managed to create nanoparticles which can cross the BBB. They made the particles out of polylactic acid, a bioplastic which is easily broken down in the body, and encapsulated them with the compound polyethylene glycol.

“A layer of polyethylene glycol (PEG) covers these nanoparticles and makes them invisible to the immune system, so they can longer circulate in the bloodstream," Prof Ramassamy explains.

The nanoparticles injected into a zebrafish travelled through blood and deposited around brain vessels © Jean-Michel Rabanel
The nanoparticles injected into a zebrafish travelled through blood and deposited around brain vessels © Jean-Michel Rabanel

Encapsulating drugs in this way could mean that patients could take much smaller doses, increasing the efficiency and reducing the risk of side effects.


The researchers tested their method on cultured cells, and then on zebrafish. "This species offers several advantages. Its blood-brain barrier is similar to that of humans and its transparent skin makes it possible to see nanoparticles' distribution almost in real time,” says Prof Ramassamy.

What is dementia?

Some 850,000 people are estimated to be living with dementia in the UK, and that’s expected to rise to two million by 2050. Most of us probably know, or have known, someone with dementia.

But we may not understand the difference between dementia and, say, Alzheimer’s disease. Dementia describes the symptoms that someone experiences as a result of a brain disease.

Such symptoms can include memory loss, mood and behavioural changes, and difficulties with thinking, problem-solving and language.

More than 100 diseases can cause dementia, each with slightly different symptoms. The most common cause of dementia is Alzheimer’s.


Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.