Scientists from Tomsk Polytechnic University (TPU) along with other researchers from Russia have managed to make cancer treatment with radioactive actinium-225 40% more effective.
According to the researchers, they have developed a special nanopackaging for actinium, which protects the body from toxic degradation products 6-10 times more effectively than its analogues. The article was published in the ACS Applied Materials & Interfaces journal.
Photo : Tomsk Polytechnic University (TPU) General therapy with the use of the Actinium-225 capsules
Actinium-225 is a radioactive isotope first discovered as a degradation product of uranium-233. As explained by the TPU scientists, this substance is considered a highly promising radiopharmaceutical for the treatment of various forms of cancer, including the most severe ones.
This is due to the fact that actinium emits alpha particles: the linear energy transfer of this type is smaller than that of beta rays, so it “hits” cancer cells more accurately without affecting healthy ones. However, actinium-225 produces toxic daughter isotopes, such as francium-221 and bismuth-213, which accumulate in liver, kidney and spleen. The researchers explain that this is what prevents actinium from being widely used in clinical practice.
Photo : Tomsk Polytechnic University (TPU) Characterisation of the capsules obtained
The solution to this problem was found by TPU researchers, who proposed 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%.
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% of the total amount in the kidneys, while the existing systems lead to the accumulation rate ranging from 30-35% to 50%. Moreover, the resistance of new capsules is 70-80% higher than that of analogues, the researchers said.
Photo : Tomsk Polytechnic University (TPU) Distribution of capsules with radionuclide after injection into a tumor in a mouse
The TPU 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. The TPU scientists used a commercially available polymer based on polypeptides and polysaccharides.