Researchers at Oregon State University created a new type of hyperthermic magnetic nanoparticle that is intended to assist in destroying tumors through localized heating under an alternating magnetic field. Previous iterations of such technologies could heat up to about 44 degrees Celsius (111 F), which was only effective in easy-to-access tumors that can be reached with a hypodermic needle, allowing a clinician to inject a large number of the nanoparticles directly into the tumour. For difficult-to-access tumors, intravenous delivery of the nanoparticles is required, but this typically only results in a small number of particles reaching the tumor, meaning their heating potential is usually not enough to cause sufficient damage. These latest particles are highly efficient at heating, reaching temperatures of up to 50 degrees Celsius (122 F), and making systemic application of such therapeutics a more feasible prospect.
Delivering magnetic nanoparticles to a tumor and then heating them up minimally invasively using an external alternating magnetic field, in the hope of destroying the tumor, is an elegant approach to cancer treatment. Indeed, researchers have been experimenting with such an approach for several years (see flashbacks below). However, the problem with this technique lies in the poor heating efficiency of the particles, with conventional magnetic particles reaching temperatures of 44 C in the vicinity of a tumor. Although this is just a few degrees higher than body temperature, it is sufficient to damage and kill tumor cells, provided enough particles are present in and around the tumor site.
This last point is key, because getting the particles into the tumor can be challenging. For more superficial and easily accessible tumors, a clinician can simply inject a large dose of the particles directly into the tumor core. However, for less accessible tumors this is not possible, so intravenous delivery is required, meaning that the particles must make their own way through the circulation and arrive at the tumor.
“With currently available magnetic nanoparticles, the required therapeutic temperatures — above 44 degrees Celsius — can only be achieved by direct injection into the tumor,” said Oleh Taratula, one of the lead developers of the new nanoparticles. “The nanoparticles have only moderate heating efficiency, which means you need a high concentration of them in the tumor to generate enough heat. And numerous studies have shown that only a small percentage of systemically injected nanoparticles accumulate in tumors, making it a challenge to get that high concentration.”
To make systemic delivery more feasible, these researchers created magnetic nanoparticles that can reach up to 50 degrees C in the tumor environment. The particles are called core-shell particles, as their core and an outer shell are made from different constituents. Specifically, the particles have a magnetite (Fe3O4) core and a maghemite (γ-Fe2O3) shell, giving them superior heating efficiency.
“To our knowledge, this is the first time it’s been shown that magnetic nanoparticles injected intravenously at a clinically recommended dose are capable of increasing the temperature of cancer tissue above 44 degrees Celsius,” said Taratula. “And we also demonstrated that our novel method could be used for the synthesis of various core-shell nanoparticles. It could serve as a foundation for the development of novel nanoparticles with high heating performance, further advancing systemic magnetic hyperthermia for treating cancer.”
Flashbacks: Nanoparticles Heat Up in Magnetic Field to Kill Cancer Tumors; Magnetic Nanoparticles Deliver Chem and Heat Cancer Cells for Synergistic Effects; Gold Nanoparticles Made to Heat Up from Near-Infrared Light for Tumor Killing; Excitable Nanoparticles Destroy Endometriosis Lesions; Diamond Nanocrystal Thermometers for Heat Ablating Nanoparticles