How Drug-loaded Nanoswimmers May Kill Cancer Cells

Our brain has the tightest security system — the Blood Brain Barrier (BBB).

It was discovered by German scientist Paul Ehrlich in 1885, when he injected blue dye into the bloodstream of mice he had been experimenting with. He found out that all of the mice’s organs had turned blue, with the exception of the brain.

Repeated experiments in later years established the truth that there’s a physical barrier that protects the brain from what it deems as harmful substances. It’s a network of small blood vessels or capillaries which are lined with endothelial cells.

However, there’s an enormous difference between the capillaries in the brain from those in the other body parts.  The endothelial cells in the brain fit very tightly together, which makes an almost impermeable boundary between the bloodstream and this very important organ.

BBB is very efficient in protecting the brain from “foreign substances” and other chemicals which must not come in contact with it.

However, it has also become a challenge to scientists how to get drugs across to the brain to be able to treat it. The blood-brain barrier blocks approximately 98 percent of potential drug treatments for brain tumors and neurological diseases.

But, there’s now a breakthrough!

An international team of researchers led by Adrian Joseph found out that asymmetric nanocarriers could swim through the blood-brain barrier using chemotactic movement.

Nanocarriers, also called nanoswimmers, are small pods often shaped like natural flagella for speedy movement.

However, to be able to direct the movement of the nanocarriers into the brain, the team made their minuscule pods asymmetrical and permeable on one side. The design makes the material inside the pod react with an external material at just one side, thereby influencing the nanocarrier to move toward the material to which it feels an attraction to.

In this case, it’s glucose, the brain’s energy source. The researchers used glucose oxidase in the nanocarriers for their mice experiment. They did also combine it with catalase in other instances to test the efficacy of chemotactic movement.

The nanocarriers responded to an external gradient of glucose.  The pods absorbed the sugar molecules and processed them. The by-products were expelled from just one side, hence pushing the pods in the opposite direction.

Moreover, the researchers used LRP1 in combination with their nanocarriers. LRP1 are proteins located in the plasma membrane of cells. The endothelial cells in the BBB contain many of these proteins, and it had made the penetration of the nanocarriers through the blood-brain barrier four times more efficient due to familiar protein constitution.

With the success of their study using asymmetrical design and chemotactic movement, the team is now experimenting with more cell-surface molecules. Their objective is to make nanocarriers reach specific types of brain cells.  According to senior author Giuseppe Battaglia, there’s a continuing increase in the gradient of glucose within blood vessels into the brain which had helped in guiding their pods through the barrier. And since that gradient is sharper around brain tumors, the team thinks they would be able to deliver the drugs to the particular area of the brain where it’s needed the most.

This discovery, according to other scientists, is indeed a remarkable achievement which will benefit many individuals suffering from brain disorders and cancer. Based on a United Nations report, more than 1 billion people are affected by various types of neurological diseases with almost 7 million deaths per year.

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