Magnetic Hyperthermia

What is Magnetic Hyperthermia?

Hyperthermia is one of the many clinical protocols used as coadjuvant therapy for cancer treatment. It has demonstrated a clear synergistic effect when combined with radiotherapy, as well as enhancing effects with numerous cytotoxic drugs.

Magnetic Hyperthermia uses a combination of alternating magnetic fields (AMF) and magnetic nanoparticles (MNPs) as heating agents. The goal of this approach is to heat specifically and exclusively the local tumor region by means of the magnetic losses of magnetic nanoparticles in an external, alternating magnetic field, doing it without damaging the surrounding healthy tissue.

Regarding the energy loss in the magnetic material, there are two different effects to be considered:

a) magnetic losses through domain wall displacements (in multi-domain particles) called Néel losses; and

b) energy loss from mechanical rotation of the particles, acting against viscous forces of the liquid medium (Brown losses).

Both effects add up so the lost energy is converted into HEAT.

Magnetic Hyperthermia is usually used as an additive therapy with standard treatments (radiotherapy, for example), and some preliminary studies have showed that the combination of radiation plus hyperthermia lead to increased results regarding tumoral regression

There are many techniques for hyperthermia involving laser, ionizing radiation, and microwaves as tools to heat up body (malignant) tissues. Although these techniques are capable of rising the intracellular temperature up to the cellular death, they may have unwanted collateral effects such as ionization of genetic material (radiation) or lack of selectiveness (microwaves) that affect the surrounding healthy tissues.

A different approach, developed mostly along the last decade, is the selective thermo-cytolysis based on the process of magnetic losses. This strategy, called magneto-thermo-cytolysis or magneto-thermoablation, is a promising technique thanks to the development of precise methods for synthesizing functionalized magnetic nanoparticles (FMNPs).

Magnetic nanoparticles with functionalized surfaces (to attach with high specificity to a given tissue) are used for hyperthermia treatments seeking their accumulation only in tumor tissue. Depending on the success in solving this biochemical and physiological challenge, cancer-specific hyperthermia protocols could be developed.

In 2010, magnetic hyperthermia trials based in the use of MNPs have passed preclinical stages and received regulatory approval as a new clinical therapy named thermotherapy.