Researchers from the State of Minas Gerais have developed a new route for the production of a material formed by magnetic iron oxide nanoparticles that might be useful to treat various kinds of cancers. This biomedical system, which is on the agenda of the major nanotechnological and medical research centers in the world, is the result of extensive research by researchers from the Chemistry Department and the Microscopy Center at the Federal University of Minas Gerais (UFMG) and from the Nuclear Technology Development Center at the National Nuclear Energy Commission (CDTN/Cnen), in the city of Belo Horizonte. The research paper was published in 2010 in the Journal of Sol-Gel Science and Technology and achieved a tremendous response in the academic community. “Thanks to the potential of our research and our good results, medicine and oncology research groups have invited us to publish our findings in scientific journals and to take part in congresses,” says physicist Nelcy Della Mohallem, a professor at UFMG and coordinator of the research project.
Nanostructured magnetic materials, such as those comprised of different forms of iron oxide, are already being used in diagnostic procedures, such as nuclear magnetic resonance (NMR), and are being tested as magnetic carriers of drugs in cancer therapy, through the use of hyperthermia, a therapy based on heating the tumor by applying a electric current magnetic field to kill the cancer cells. These therapies use two major advantages of iron oxide: its low toxicity for humans and the possibility of controlling its magnetization. Formed by magnetite nanoparticles – this magnetic material is comprised of iron oxides – inserted into a silica matrix, the nanocomposite is synthesized in the form of powder or monolith, the small part used in implants of bones affected by tumors. The material has regular pores, whose diameter ranges from 2 to 50 nanometers – hence the name mesoporous – that can be filled with various kinds of pharmaceuticals. An important step in the process is the size of the pores, because they must fit the size of the drug’s molecule. The researchers from Minas Gerais are testing a drug called doxorubicin on the material; doxorubicin is a drug used in chemotherapy for various kinds of cancer. “The encapsulation of a drug of this kind is important because of its toxicity. When the drug is encapsulated and released in a controlled manner, we manage to reduce the side effects on the patient,” says Nelcy.
In hyperthermia therapy, the nanocomposite need not be filled with pharmaceuticals necessarily, as the tumor can be destroyed by increasing the temperature at the site of the tumor. The way this works is simple. When the material reaches the tumor, an external magnetic field, generated by a specific device used for this end, is applied to the patient. Depending on the site of the injury, the material can be injected with a needle or carried through the blood stream with the help of external magnetism. The magnetic field makes the magnetic particles in the nanocomposite vibrate and warm up. “A temperature of five degrees Celsius (ºC) above the body temperature is enough to destroy the tumor without affecting the surrounding cells,” says Nelcy. “But the composite has to be very well controlled, because particles such as the magnetite particles can warm up to a temperature of 20o C above the body temperature when they are submitted to a magnetic field and damage the healthy cells,” she says. To be efficient and increase the temperature within the targeted range, the nanocomposite must be impregnated with magnetite particles, whose size, distribution, and concentration must be well defined.
The action is slightly different in the case of controlled drug release. When the drug reaches the tumor, the magnetic field is applied and the vibration of the magnetic particles triggers the gradual release of the drug contained in its pores. In some cases, the two treatments can be applied simultaneously. The heat attacks the cancer cells, while the drug acts to avoid the rejection of the material or to prevent infection. “Our nanocomposites are covered with silica, which is why they are metabolized by the liver and expelled by the body.”
One of the team’s accomplishments is the material’s synthesis route adopted by the group, which also includes researcher Edésia de Sousa, from CDTN/Cnen, and chemistry student Karynne Souza, who is attending a PhD program at the Laboratory of Nanostructured Materials at UFMG. “This is a very efficient and simple route. We tested the material and it worked very well within the targeted temperature range for the treatment of cancer,” says Nelcy. The nanocomposite was made by impregnating the SBA-15 mesoporous silica with a solution containing ferric sulfate, Fe2(SO4)3. In vitro tests have been conducted. The group hopes to begin tests on animals shortly; these will be followed by clinical tests on humans. “Our idea is to pass on the process and the nanocomposite to a pharmaceutical company, because a spin-off company – which we could set up – would have a lot of difficulty putting the product on the market,” says Nelcy. All these procedures are high-cost and call for high investment.
SOUZA, K.C. et al. Mesoporous silica-magnetite nanocomposite: facile synthesis route for application in hyperthermia. Journal of Sol-Gel Science and Technology. v. 53, n. 2, p. 418-27. 2010.