- Ultrathin needles, as thin as human hair can now be used to deliver small quantities of medicine directly to the brain.
- Directly targeting specific
regions of the brain can treat the precise neural
circuits without interfering with normal body function.
- The extremely small cannula allows
the delivery of drugs to only about a cubic millimeter of the brain,
limiting exposure of the drug to unspecific brain regions.
Using an ultrathin needle as thin as the human hair, a research team at
MIT has been able to deliver tiny
quantities of medication directly into brain regions as small as 1 cubic
millimeter. This allows targeting very specific areas deep inside the brain with precise control without
letting the drugs enter the central nervous system or interfere with normal body functions. The study
was published in the journal Science Translational Medicine
A miniaturized system
The device contains several tubes encapsulated within a needle. Using
microfabrication techniques, the tubes were developed to measure about 30
micrometers in diameter and up to 10 centimeters in length. The tubes are
contained in a stainless steel needle with a diameter of about 150 microns. The
tubes may contain one or more drugs that can be directed towards specific
regions in the brain with precise control of how much of the drug is given and where it goes. In
an experiment on rats, the team was successfully able to deliver targeted doses
of a drug that affects the animals' motor function.
"We can infuse very small amounts of multiple drugs compared to what
we can do intravenously or orally, and also manipulate behavioral changes
through drug infusion," says Canan Dagdeviren, the lead author of the
The problem with central nervous system drugs
Drugs used to treat
brain disorders are generally orally taken and act on the central nervous
system. These drugs interact with neurotransmitters in the brain, sometimes
causing undesired effects on undesired brain regions. For example, while
l-dopa, a dopamine
precursor used to treat Parkinson's
disease function by boosting serotonin levels in patients with depression, it
can have side effects because it acts throughout the brain.
‘Using an ultrathin cannula, tiny quantities of drugs can be delivered directly into specific brain regions with precise control.’
"One of the
problems with central nervous system drugs is that they're not specific, and if
you're taking them orally they go everywhere. The only way we can limit the
exposure is to just deliver to a cubic millimeter of the brain, and in order to
do that, you have to have extremely small cannulas," Michael Cima,
co-author of the study says.
In an experiment in mice, the team delivered a drug called muscimol to
the substantia nigra, a brain region located deep within the brain that helps
control movement. The cannulas were connected to small pumps that could be
implanted under the skin. Using these pumps tiny doses of over hundreds of
nanoliters could be delivered into the brains of rats.
Muscimol induces symptoms similar to those seen in Parkinson's disease
. When the drug was
delivered with the miniaturized delivery needle to the rat brain, the team was
able to generate Parkinson's symptoms including stimulating the rats to
continually turn in a clockwise direction. They were also able to halt the
Parkinsonian behavior by delivering a dose of saline through a different
channel, to wash the drug away.
"Since the device can be customizable, in the future we can have
different channels for different chemicals, or for light, to target tumors or
neurological disorders such as Parkinson's disease or Alzheimer's,"
The study reports that the cannulas can be fabricated in nearly any
length and thickness, which makes it possible to create the right size for the
different brain regions they target. The success in rats could one day
translate into human brains.
- C. Dagdeviren el al., "Miniaturized neural system for chronic, local intracerebral drug delivery," Science Translational Medicine (2018), DOI: 10.1126/scitranslmed.aan2742