Decrease In Specific Absorption Rate Research Articles

A nudge over the relaxation plateau: effect of pH, particle concentration, and medium viscosity on the AC induction heating efficiency of biocompatible chitosan-coated Fe3O4 nanoparticles

The effects of pH, MNP concentration, and medium viscosity on the magnetic fluid hyperthermia (MFH) properties of chitosan-coated superparamagnetic Fe3O4 nanoparticles (MNPs) are probed here. Due to the protonation of the amide groups, the MNPs are colloidally stable at lower pH (∼2), but form aggregates at higher pH (∼8). The increased aggregate size at higher pH causes the Brownian relaxation time (τ B) to increase, leading to a decrease in specific absorption rate (SAR). For colloidal conditions ensuring Brownian-dominated relaxation dynamics, an increase in MNP concentrations or medium viscosity is found to increase the τ B. SAR decreases with increasing MNP concentration, whereas it exhibits a non-monotonic variation with increasing medium viscosity. Dynamic hysteresis loop-based calculations are found to be in agreement with the experimental results. The findings provide a greater understanding of the variation of SAR with the colloidal properties and show the importance of relaxation dynamics on MFH efficiency, where variations in the frequency-relaxation time product across the relaxation plateau cause significant variations in SAR. Further, the in vitro cytotoxicity studies show good bio-compatibility of the chitosan-coated Fe3O4 MNPs. Higher SAR at acidic pH for bio-medically acceptable field parameters makes the bio-compatible chitosan-coated Fe3O4 MNPs suitable for MFH applications.

Size-controlled heating ability of CoFe 2 O 4 nanoparticles for hyperthermia applications

Abstract The magnetic properties and heating capacity of cobalt ferrite (CoFe2O4) nanoparticles 13–24 nm in size were studied. Results showed that the specific absorption rate of the nanoparticles strongly depended on their magnetic properties and particle size. Specific absorption rate values decreased with increased particle size, and the smallest CoFe2O4 nanoparticles (13.5 nm) exhibited the highest specific absorption rate. The mechanism underlying the decrease in specific absorption rate of the CoFe2O4 nanoparticles with increased particle size was also discussed.

Modulation of Interparticle Interactions and Specific Absorption Rate in Magnetomicelles through Changes in the Molecular Weight of the Hydrophobic Polymer Block

Magnetomicelles are amphiphilic block copolymer micelles, which contain magnetic nanoparticles in the core. Magnetomicelles have been proposed as magnetic fluid hyperthermia agents for cancer treatment. Magnetic interactions between nanoparticles within a micelle affect the amount of heat that they dissipate. Here, magnetomicelles are prepared varying the molecular weight of the core‐forming polymer block. The magnetomicelles are magnetically characterized in liquid suspensions and embedded in a polymer matrix. The results show that as the molecular weight of the core‐forming polymer block increases, both the interparticle magnetic interactions and specific absorption rate decrease. This is probably due to mixing between the polymer and the magnetic nanoparticles, which increases the interparticle distance.