The researchers claim to have developed a unique nanopackaging for actinium that protects the body from toxic degradation products six to ten times more effectively than analogues.
Actinium-225 is a radioactive isotope that was identified as a byproduct of uranium-233 decay. According to the researchers, this chemical is a highly promising radiopharmaceutical for the treatment of various types of cancer, including the most severe.
As actinium emits alpha particles, which have a lower linear energy transfer than beta rays, and hence “target” cancer cells more precisely without damaging healthy cells. Actinium-225, on the other hand, produces hazardous daughter isotopes such as francium-221 and bismuth-213, which accumulate in the liver, kidney, and spleen. This is why actinium is not commonly utilised in clinical practice.
Now, the team has found a unique method of isotope packaging into a polymer-protein capsule. According to them, it helps neutralise toxic isotopes and increase the therapeutic effect of actinium-225 by 40%.
Actinium is considered a universal isotope, and in theory it can be used to treat all types of cancer provided that the problem of toxicity is solved. Our method involves the use of a biodegradable polymer: the capsule decays into harmless elements after francium-221 and bismuth-213 decay into harmless isotopes
explained the author of the study.
The half-life of actinium-225 is 10 days and the capsule remains intact for at least two weeks. Animal testing has shown the accumulation of no more than 5 percent of the total amount in the kidneys, while the existing systems lead to the accumulation rate ranging from 30-35 percent to 50 percent. Moreover, the resistance of new capsules is 70-80 percent higher than that of analogues, the researchers said.
The researchers explain that nowadays the physical method is commonly used for actinium packaging: the isotope is simply mixed with porous polymer nanospheres, “locking” most of it inside. However, the structure has proven itself unreliable, they noted.
When creating new capsules, the authors used chemical methods, first binding actinium to albumin, a protein molecule, and then placing it in a polymer solution. Albumin creates a strong covalent bond with the polymer, literally surrounding the isotope with a protective sphere.
Scientists used a commercially available polymer-based on polypeptides and polysaccharides.
The article was published in the journal Applied Materials & Interfaces.
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