Magnetic fluid hyperthermia has been recently considered as a Renaissance of cancer treatment modality due to its remarkably low side effects and high treatment efficacy compared to conventional chemotheraphy or radiotheraphy. However, insufficient AC induction heating power at a biological safe range of AC magnetic field (H ·f < 3.0-5.0 × 10 A m s ), and highly required biocompatibility of superparamagnetic nanoparticle (SPNP) hyperthermia agents are still remained as critical challenges for successful clinical hyperthermia applications. Here, newly developed highly biocompatible magnesium shallow doped γ-Fe O (Mg -γFe O ) SPNPs with exceptionally high intrinsic loss power (ILP) in a range of 14 nH m kg , which is an ≈100 times higher than that of commercial Fe O (Feridex, ILP = 0.15 nH m kg ) at H ·f = 1.23 × 10 A m s are reported. The significantly enhanced heat induction characteristics of Mg -γFe O are primarily due to the dramatically enhanced out-of-phase magnetic susceptibility and magnetically tailored AC/DC magnetic softness resulted from the systematically controlled Mg cations distribution and concentrations in octahedral site Fe vacancies of γ-Fe O instead of well-known Fe O SPNPs. In vitro and in vivo magnetic hyperthermia studies using Mg -γFe O nanofluids are conducted to estimate bioavailability and biofeasibility. Mg -γFe O nanofluids show promising hyperthermia effects to completely kill the tumors.

The magnetization dynamics involved in applying an alternating field are composed of a superposition of Neél and Brownian relaxations. To evaluate the mechanisms of magnetic relaxations, it is necessary to individually evaluate the Neél and Brownian regimes. In this study, by applying a fast responding pulse field, the two-step magnetization response of magnetic nanoparticles dispersed in a fluid in the Brownian regime occurred after the Neél regime. We isolated Neél and Brownian relaxations from an experimentally observed superposition relaxation system by fitting the theoretical calculation to the measured time evolution response of the magnetization, which was in agreement with the susceptibility that was measured through applying an alternating magnetic field. The dependence of Neél and Brownian relaxation's dominance in the superposition system on relaxation times was clearly observed. In particular, the effect of dipole interactions on Neél and Brownian relaxation times were confirmed by changing the particle concentration in a magnetic fluid. Elucidation of the transition process from Neél to Brownian relaxation, which is influenced by the proportion between Neél and Brownian relaxation times and the effect of dipole interactions on the individual relaxation processes, allows us to develop optimal magnetic nanoparticles for a variety of biomedical applications.

Image-guided drug delivery is an emerging strategy in the field of nanomedicine. The addition of image guidance to a traditional drug delivery system is expected to achieve highly efficient treatment by tracking the drug carriers in the body and monitoring their effective accumulation in the targeted tissues. In this study, we developed multifunctional magneto-plasmonic liposomes (MPLs), a hybrid system combining liposomes and magneto-plasmonic nanoparticles for a triple-modality image-guided drug delivery. Tenofovir disoproxil fumarate, an antiretroviral drug used to treat human immunodeficiency virus type 1 (HIV-1), was encapsulated into the MPLs to enable the treatment in the brain microenvironment, which is inaccessible to most of the drugs. We found strong negative and positive contrasts originating from the magnetic core of MPLs in magnetic resonance imaging (MRI) and magnetic particle imaging (MPI), respectively. The gold shell of MPLs showed bright positive contrast in X-ray computed tomography (CT). MPLs achieved enhanced transmigration across an in vitro blood-brain barrier (BBB) model by magnetic targeting. Moreover, MPLs provided desired therapeutic effects against HIV infected microglia cells.

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Magneto-plasmonic nanoparticles are one of the emerging multi-functional materials in the field of nanomedicine. Their potential for targeting and multi-modal imaging is highly attractive. In this study, magnetic core / gold shell (MNP@Au) magneto-plasmonic nanoparticles were synthesized by citrate reduction of Au ion on magnetic nanoparticle seeds. Hydrodynamic size and optical property of magneto-plasmonic nanoparticles synthesized with the variation of Au ion and reducing agent concentrations were evaluated. The synthesized magneto-plasmonic nanoparticles exhibited superparamagnetic property, and the magnetic property contributed to the concentration-dependent contrast in magnetic resonance imaging (MRI). The imaging contrast from the gold shell part of magneto-plasmonic nanoparticles was also confirmed by X-ray computed tomography (CT). The transmigration study of magneto-plasmonic nanoparticles using an in vitro blood–brain barrier (BBB) model proved enhanced transmigration efficiency without disrupting integrity of the BBB, and showed potential to be used for brain diseases and neurological disorders.