Key Points

The new system, being developed by a team of Stanford University researchers, uses nanoparticles to encapsulate drugs along with ultrasound to unleash the drugs at their intended destinations.

In a study published in the journal Nature Nanotechnology, the team showed in rats that their system can deliver ketamine to specific regions of the brain and painkillers to specific nerves in limbs. Using a new sucrose formulation, they found that nanoparticles are safer, more stable, and easier to produce.

“Turns out just a little bit of sugar is all you need to make this work,” said Raag Airan, Assistant Professor of radiology, Stanford Medicine.

The researchers found that a 5 per cent sucrose solution inside the nanoparticles made them relatively stable in the body, yet responsive to ultrasound stimulation.

That means that even when the nanoparticles are delivered into the bloodstream and travel throughout the body, most of the drug is released only where it’s needed. A narrow beam of ultrasound, externally applied, pinpoints the target, releasing the drug.

Such a system has the potential to make a wide range of drugs safer and more effective.

“We can maximise the therapeutic effect and minimise the off-target effects,” Airan said.

Initially, the nanoparticles consisted of a polymer shell filled with a liquid core of uncommon chemical compounds. But as it did not work, the team tried adding a variety of common substances to the liquid core, from polymers to salts, to modulate its response to ultrasound.

Finally, they tried sugar. After testing different types and concentrations of sugars, the researchers found that 5 per cent sucrose added to the liquid core achieved the best balance of ultrasound response and stability at body temperature.

The researchers then tested the drug delivery system in rats, comparing animals that were given an injection of free, unencapsulated ketamine with those given ketamine encapsulated in nanoparticles with 5 per cent sucrose.

When the researchers applied ultrasound to a particular brain region, the nanoparticles delivered about three times as much drug to that region as to other parts of their brain -- demonstrating targeted drug release.

If the system works in humans, clinicians may be able to isolate the emotional effects of ketamine -- to treat depression, for example -- while blocking the dissociative effects of the drug, the researchers said.

- IANS