Nanomedicine Slips Through The Cracks To Fight Cancer

Scientists in Japan have devised a nanoparticle carrier for siRNA that can access hard-to-reach tumors, such as those of the pancreas and the brain.

AsianScientist (May 10, 2019) – In a study published in Nature Communications, a research group in Japan has found a way to deliver specific drugs to tumors in parts of the body that are exceptionally difficult to access.

The battle against cancer is fought on many fronts. One promising field is gene therapy, which targets genetic causes of diseases to reduce their effect. The idea is to inject a nucleic acid-based drug into the bloodstream—typically small interfering RNA (siRNA)—which binds to a specific problem-causing gene and deactivates it. However, siRNA is very fragile and needs to be protected within a nanoparticle or it breaks down before reaching its target.

Researchers led by Associate Professor Kanjiro Miyata at the University of Tokyo, Japan, thus developed a Y-shaped block catiomer (YBC) that can bind to therapeutic materials, forming a package 18 nanometers wide. This is more than five times smaller than most existing nanoparticles which are about 100 nanometers wide.

The YBC is so-called because it has two component molecules of polymeric materials connected in a Y-shape formation. It has several sites of positive charges, which bind to negative charges in siRNA. The number of positive charges in YBC can be controlled to determine which kind of siRNA it binds with. When YBC and siRNA are bound, they are called a unit polyion complex (uPIC).

Due to their small size of less than 20 nanometers, the YBCs are able to squeeze into hard-to-reach tumors. For example, pancreatic tumors are usually surrounded by fibrous tissues, and cancers in the brain are wrapped around by tightly connected vascular cells. The YBC, being small enough, can slip through these gaps in the tissues to deliver siRNAs into the tumor.

“The most surprising thing about our creation is that the component polymers are so simple, yet uPIC is so stable,” said Miyata. “It has been a great but worthy challenge over many years to develop efficient delivery systems for nucleic acid drugs. It is early days, but I hope to see this research progress from mice to help people with hard-to-treat cancers one day.”

The article can be found at: Watanabe et al. (2019) In Vivo Rendezvous of Small Nucleic Acid Drugs With Charge-matched Block Catiomers to Target Cancers.


Source: University of Tokyo; Photo: Shutterstock.
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