Throughout cinematic history, there have been examples of microscopic robots that reached unhealthy organs through the bloodstream and cured them. Today, this cinematic fiction is already reality, and it could become standard medical practice.
Taking drugs is not a problem for most of us but making sure that the drug reaches only the organ for which it was intended to take effect and minimize side-effects is the dream of all medical researchers.
There’s one organ in particular that is particularly difficult to reach if you simply ingest a drug or inoculate it intravenously; this organ is the brain.
Why is it so difficult to deliver drugs directly to nerve cells?
The reason lies in the presence of the blood-brain barrier, which is a physical structure positioned specifically to protect the brain. Its function is to regulate, in a selective way, the passage of potentially dangerous substances or microorganisms from the bloodstream to the brain (and vice versa). In this way, it protects the central nervous system from possible infections or intoxications by acting as a “valet” that allows the passage only to those who have the key (i.e. small molecules such as amino acids, glucose, water and lipophilic molecules).
If its function is very important in preventing the passage of viruses or bacteria, such as in cases where you wish to administer a drug that must reach the nerve cells to treat a brain tumor, it’s definitely an obstacle. In fact, injecting the drug into the bloodstream is not enough to overcome the blood-brain barrier.
Over time, various approaches have been studied and the most innovative and futuristic was recently published in the scientific journal Science Robotics by a team of Chinese researchers from Harbin Institute of Technology, together with First Affiliated Hospital of Harbin Medical University.
Like a Trojan horse
In order to overcome the blood-brain barrier, the team of Chinese researchers wondered about what normally crosses the blood-brain barrier. The answer was a specific cell of the immune system called a neutrophil or white blood cell.
The researchers then adopted a Trojan Horse-like technique, which is to expose groups of neutrophils to tiny pieces of magnetic nanogel particles (vessels that contain the drug) coated with fragments of material from E. coli (a very common bacterium in the human body). After exposure, neutrophils naturally enveloped the shuttles, believing them to be nothing more than E. coli bacteria. Neutrophils containing the vessels were then injected into the bloodstream of a mouse that had a brain tumor. The team then applied a magnetic field through which they directed the neutrophils across the blood-brain barrier, which they were able to pass, as these neutrophils were recognized as “normal” neutrophils by the immune system.
At this point, once across the blood-brain barrier, the vessels were able to release the anti-tumor drug.
The next step will be to test this drug delivery technique on human patients, to improve the effectiveness of the treatment of brain tumors.
The following link is for the trailer of “Fantastic Voyage” (1966), probably the first movie of its kind, describing the science fiction journey inside the human body.
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