Hot magnets that kill cancer cells while sparing healthy ones

In the previous edition of Quantum , you read about using magnetism to help refrigeration or cooling. So, then, can the heating properties of magnetism be far behind?

Magnetic hyperthermia — generating heat in magnetic nanoparticles by applying alternating magnetic fields on them — has been an area of research in cancer therapy since the 1990s.

The goal is to burn away cancer cells. Conventional treatments such as chemotherapy do that, but they also kill adjoining healthy cells, with severe side effects.

Dr Kavita Srikanti, a scientist with the Hyderabad-headquartered International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), has used magnets to treat cancer with some success. (Srikanti and her mentor Dr R Gopalan have worked extensively on magnets for various applications.)

At the heart of the research is the use of ‘magnetocaloric materials’ — which heat up when inside a magnetic field and cool when pulled out. Why not use the materials’ heat to burn cancer cells?

The use of magnets in cancer treatment — ‘magnetic hyperthermia’ — has been explored earlier through clinical trials in China, Europe and the US. “However, due to problems like heating efficiency and side effects, there is no in-vivo (within a living organism) practice these days,” Srikanti told Quantum .

ARCI’s work fine-tunes the science for better effect. How?

In conventional magnetic hyperthermia, magnetic nanoparticles are subjected to alternating magnetic fields (of a few gauss), which produces heat due to magnetic relaxation losses. Usually, the temperature required to kill tumor cells is 40-46 degree C. However, the drawback here is the lack of temperature control, which may damage healthy cells and cause side effects like increased blood pressure.

Magnetocaloric materials, on the other hand, provide controlled and self-regulated heating. Moreover, they cool down as soon as the magnetic field is removed, unlike the magnetic nanoparticles, which remain overheated even after the removal of the magnetic field.

The ARCI team chose a rare-earth based alloy for studies as some rare earth materials are compatible with the human body. They optimised the alloy composition such that the ‘Curie temperature’ (the point at which magnetic materials undergo a change in their magnetic properties) came close to the therapeutic range (42-46 degree C) required for destroying cancer cells.

This method, when used in conjunction with radiation therapy, would reduce both side effects and treatment time.

Srikanti’s work has been published in the Journal of Alloys and Compounds . However, the research is still some way from reaching fruition, for there are some hurdles to cross. For instance, when Srikanti’s research led her to test deionised water as a medium to inject the heated magnetocaloric material into cells, the temperature of the material declined from 45 to 38 degree C, which isn’t enough to kill cancerous tissue. The minimum temperature required for cancer therapy is 42°C.

So, what gave Srikanti the confidence in her research? During lab tests on cell lines in dry conditions — that is, the stage before testing with deionised water — “it was seen that heating was specific to the tissues that were injected with these materials and did not cause damage to adjoining tissues.” This is progress, even though it’s just the first step.

The question that pops up is: Why not keep applying and removing magnetic fields to keep the heat up? Srikanti insists that the team “has applied the maximum field available in the hyperthermia set-up”. Also, it is clearly not possible to heat up the liquid (the medium that takes the magnetocaloric materials to the cancerous cells) to the required temperature, because the recipients are humans who are already in pain, and we cannot have hot liquids coursing through their veins, says Srikanti.

She is also keen to clarify that when they become effective in the real world, magnetocaloric materials are best served alongside radiation. “It is a complementary approach.”

Narrowing down on the ideal injecting medium and the ways to ensure the materials reach even inaccessible tumors, are the subjects of her subsequent research.

She says, “I would like to progress at least till the level of testing successfully on mice.”

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