Radio-frequency-heating capability of silica-coated manganese ferrite nanoparticles

MnFe₂O₄ nanoparticles (NPs) with various sizes and tight size-distribution were synthesized by a chemical solution-phase method. The as-synthesized NPs were coated with a silica shell of 4 nm-5 nm in thickness, enabling the water-solubility and biocompatibility of the NPs. The MnFe₂O₄ NPs with a size of less than 18 nm exhibit superparamagnetic behavior with high saturated magnetization. The capacity of the heat production was enhanced by increasing particle sizes and radio frequency (RF) field strengths. MnFe₂O₄/SiO₂ NPs with 18-nm magnetic cores showed the highest heat-generation ability under an RF field. These MnFe₂O₄/SiO₂ NPs have great potentiality to cancer treatments, controlled drug releases, and remote controls of single cell functions.