A novel method for tumour ablation using implanted magnesium alloy rods has been developed. The rods induce tumour destruction via eddy current heating induced by an external alternating magnetic field.
Magnetic hyperthermia therapy (MHT) is an experimental cancer therapy that utilises magnetocaloric agents to destroy tumours. During MHT, magnetocaloric agents (typically magnetic nanoparticles) are administered into tumours, and an external alternating magnetic field (AMF) is applied, which causes the nanoparticles to generate heat, ablating the tumours.
MHT is a non-invasive local treatment strategy and is carries certain advantages over other hyperthermal therapies, notably that there is no limit to the depth of tissue it can penetrate, and that is does not heat surrounding, non-targeted tissue.
Despite this, clinical use is rare as the magnetic nanoparticles currently used can only be heated effectively under strong AMFs and carry some safety concerns. Therefore, there is a demand for new magnetocaloric agents which have stronger AMF-induced heating and excellent biocompatibility.
In an article published in the National Science Review, Professors Zhuang Liu and Liang Cheng from Soochow University reported the use of a non-magnetic magnesium alloy (MgA) as a novel MHT agent. They utilised the eddy thermal effect of bulk conductors within an AMF as a heating mechanism, rather than the relaxation loss of metal nanoparticles.
In bulk conductors, such as metals, an eddy current is induced within the material when it is placed in an AMF. This induced current generates heat, and the thermal effect is particularly strong when the resistivity of the material is low. As this method of heating is so effective, only a low field intensity AMF is required to generate sufficiently high temperatures.
The researchers demonstrated that MgA rods, composed of magnesium, zinc and calcium with a ratio of 97.7: 2.0: 0.3 respectively, were able to destroy tumour cells in vitro and in vivo effectively and accurately.
MgA rods were implanted into, and successfully destroyed, mouse tumours upon exposure to a low-intensity AMF. This was repeated with larger VX2 tumours in rabbits to the same effect. The implanted MgA rods showed excellent biocompatibility and approximately 20 percent of their mass had degraded after three months.
This study is the first example of MgA being used for tumoricidal purposes, broadening its applications in biomedicine. It provides a new strategy for accurate and effective tumour treatment under a low-field-intensity AMF in a minimally invasive manner and works for deep-set and large tumours. As MgA is already a popular material for medical implants, further development of this technique holds great promise for clinical translation.