Magnetic nanoparticle-loaded polymer nanospheres as magnetic hyperthermia agents

Uniform magnetic nanoparticle-loaded polymer nanospheres with different loading contents of manganese ferrite nanoparticles were successfully synthesized using a flexible emulsion process. The MnFe₂O₄-loaded polymer nanospheres displayed an excellent dispersibility in both water and phosphate buffer saline. The effect of loading ratio and size of MnFe₂O₄ nanoparticles within the nanospheres on the specific absorption rate (SAR) under an alternating magnetic field was investigated. Our results indicate that a large size (here 18 nm) and a low loading ratio are preferable for a high SAR. For a smaller particle size (6 nm), the low loading ratio did not result in an enhancement of the SAR value, while a very low SAR value is expected for 6 nm. In addition, the SAR of low-content MnFe₂O₄ (18 nm)-loaded polymer nanospheres in the agarose gel which is simulated for in vivo environment is the highest among the samples and does not change substantially in physiological environments. This differs largely from the behaviour of singly dispersed nanoparticles. Our results have paved the way for the design of MnFe₂O₄-loaded polymer nanospheres as magnetic hyperthermia agents for in vivo bio-applications.