Iron Oxide Nanorings and Nanotubes for Magnetic Hyperthermia: The Problem of Intraparticle Interactions.

Raja Das,Javier Alonso Masa,Manh-Huong Phan,José Ángel García,Eneko Garaio,Irati Rodrigo,Zohreh Nemati,Vijaysankar Kalappattil,Hariharan Srikanth

doi:10.3390/nano11061380

Abstract

Magnetic interactions can play an important role in the heating efficiency of magnetic nanoparticles. Although most of the time interparticle magnetic interactions are a dominant source, in specific cases such as multigranular nanostructures intraparticle interactions are also relevant and their effect is significant. In this work, we have prepared two different multigranular magnetic nanostructures of iron oxide, nanorings (NRs) and nanotubes (NTs), with a similar thickness but different lengths (55 nm for NRs and 470 nm for NTs). In this way, we find that the NTs present stronger intraparticle interactions than the NRs. Magnetometry and transverse susceptibility measurements show that the NTs possess a higher effective anisotropy and saturation magnetization. Despite this, the AC hysteresis loops obtained for the NRs (0–400 Oe, 300 kHz) are more squared, therefore giving rise to a higher heating efficiency (maximum specific absorption rate, SARmax = 110 W/g for the NRs and 80 W/g for the NTs at 400 Oe and 300 kHz). These results indicate that the weaker intraparticle interactions in the case of the NRs are in favor of magnetic hyperthermia in comparison with the NTs.

Highlights

Cancer treatment through magnetic hyperthermia relies on delivering magnetic nanoparticles (MNPs) to a tumor area in order to deactivate cancer cells by locally raising the temperature while avoiding collateral damage to healthy tissues [1,2,3,4]
The NRs seemed to consist of semispherical nanograins of around 17 nm while the NTs were composed of nanorod-like units, 70 ± 20 nm long and 7 ± 3 nm wide, bound together as we already described in [39]
We found that the lower concentration of NaH2 PO4 ·2H2 O promoted the growth of the NTs and the higher concentration of NaH2 PO4 ·2H2 O promoted the growth of the NRs

Summary

Introduction

Cancer treatment through magnetic hyperthermia relies on delivering magnetic nanoparticles (MNPs) to a tumor area in order to deactivate cancer cells by locally raising the temperature while avoiding collateral damage to healthy tissues [1,2,3,4] Since it was proposed by Gilchrist et al in 1957 [5], the technique has progressively advanced and nowadays there are already a few clinical trials being carried out in different hospitals around the world [3,6]. Concerning this last issue, one of the most complex problems that arises in the effort of increasing the SAR is the problem of magnetic interactions [16,17]. Interparticle magnetic interactions appear when the separation between the individual MNPs is small enough

Methods

Results

Conclusion