Working with colleagues in the Czech Republic and the United States, TalTech researchers developed a nanodiamond‑based drug carrier that was able to cross a blood–brain barrier model in laboratory tests. Although the solution is still in an early stage of development, the same principle could in the future help deliver other medicines to the brain that are currently difficult to transport into the central nervous system.

Why is it so hard to deliver drugs to the brain?

The human brain is protected by the blood–brain barrier, whose job is to keep the brain's sensitive environment stable. The barrier allows necessary substances to enter the brain but blocks many other molecules, including medicines.

This complicates treatment for poisoning by several nerve agents — such as sarin, Novichok and VX — and certain pesticides. Nerve agents can paralyze the human nervous system within minutes because they block an enzyme called acetylcholinesterase (AChE), which helps nerve cells transmit signals. When the enzyme is blocked, seizures and respiratory failure quickly develop, leading to death.

Oximes, used as antidotes, can successfully restore enzyme activity in the peripheral nervous system, but their effect in the central nervous system has been limited. Because oxime molecules are positively charged, they struggle to cross the blood–brain barrier. As a result, the drug may save the patient's life but not prevent brain damage. Oximes have been used for more than 50 years, but no effective solution has been found for delivering them into the brain.

Under the leadership of senior researcher Yevgen Karpichev, head of the Sustainable Chemistry and Technology research group, scientists attempted to deliver the antidote to the brain using nanodiamonds. They found that oximes attached to nanodiamonds were able to cross a blood–brain barrier model in vitro. In addition, they restored the activity of AChE blocked by nerve agents in the central nervous system.

Nanodiamonds as drug carriers

Nanodiamonds are produced through controlled explosions and measure only about five nanometers in diameter. For comparison, a human hair is roughly 60,000–80,000 nanometers thick. Their usefulness in drug delivery is not only due to their size.

The crystals have a very stable and chemically resistant structure. They degrade slowly and do not react randomly with other molecules. At the same time, their surface can be chemically modified to attach various molecules, including medicines.

Researchers have submitted a U.S. patent application for the technology. "Our study showed that nanodiamonds can help nerve‑agent antidotes cross the blood–brain barrier as carriers. This is only the first stage of research. We will continue developing nanocarriers to improve their efficiency and expand their use in biomedicine," said Karpichev. "The same technology could in the future be used with other drugs that are currently difficult to deliver to the brain, such as treatments for neurodegenerative diseases or tumors."

The article was published in the journal Chemico‑Biological Interactions.

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