Drug delivery in a nasal spray might open a direct route to the brain
Locusts and humans don't have a lot of physical similarities. But peer inside our noggins, and our blood-brain barriers – a protective shield that prevents harmful particles from entering the brain – share a useful anatomical likeness. Scientists have successfully used the brains of these tropical grasshoppers as a testbed for a new type of drug delivery, one that could see life-saving medicines carried directly to the brain by way of a simple sniff.
The blood-brain barrier is a protective membrane that surrounds vessels in the brain to protect it from foreign substances that may cause harm. But the trouble is, it stops 98 percent of therapeutic molecules from entering at the same time, presenting a major roadblock to the treatment of brain disease.
Researchers have made some promising advances in this area, with ultrasound techniques that help open the door and engineered fat cells that can make it through on their own. But by and large, getting drugs to this part of the brain is invasive and tricky business. Engineers at Washington University in St. Louis, however, say that they have come up with a nasal-spray-like technology that could make things much, much simpler.
The team, led by research scientist Ramesh Raliya, developed an aerosol made up of gold nanoparticles. These were crafted to a certain size and shape, and were tagged with fluorescent markers so the researchers could track their movement.
The team then exposed locusts to the aerosol spray and watched the nanoparticles travel through their antennas, olfactory nerves and blood-brain barrier, before spreading throughout the brain in a matter of minutes. This is promising, and not just because the blood-brain barriers of locusts and humans have anatomical similarities. Administering drugs through the nasal passage is considered the most direct route to the brain.
"The shortest and possibly the easiest path to the brain is through your nose," said Barani Raman, associate professor of biomedical engineering at Washington University. "Your nose, the olfactory bulb and then olfactory cortex: two relays and you've reached the cortex."
Investigating potential side effects of the approach in regular brain function, the team examined the physiological response of the olfactory neurons in the locusts before and several hours after exposure to the aerosol, finding no noticeable changes.
With what appears a promising new delivery mechanism, the next step for the researchers is to fuse different medicines to the gold nanoparticles so they can hitch a ride in the fast lane to the brain. They will also explore using ultrasound for guided delivery to target certain regions, something that could prove useful in brain-tumor treatment. Ultimately, this could lead to a drug-delivery method that is no less comfortable than treating a blocked nose.
"This would be a nanoparticle nasal spray, and the delivery system could allow a therapeutic dose of medicine to reach the brain within 30 minutes to one hour," said Raliya.
The team's research was published in the journal Scientific Reports.