Unraveling viscosity effects on the hysteresis losses of magnetic nanocubes

Abstract

Hysteresis losses in magnetic nanoparticles constitute the basis of magnetic hyperthermia for delivering a local thermal stress. Nevertheless, this therapeutic modality is only to be realised through a careful appraisal of the best possible intrinsic and extrinsic conditions to the nanoparticles for which they maximise and preserve their heating capabilities. Low frequency (100 kHz) hysteresis loops accurately probe the dynamical magnetic response of magnetic nanoparticles in a more reliable manner than calorimetry measurements, providing conclusive quantitative data under different experimental conditions. We consider here a set of iron oxide or cobalt ferrite nanocubes of different sizes, through which we experimentally and theoretically study the influence of the viscosity of the medium on the low frequency hysteresis loops of magnetic colloids, and hence their ability to produce and dissipate heat to the surroundings. We analyse the role of nanoparticle size, size distribution, chemical composition, and field intensity in making the magnetisation dynamics sensitive to viscosity. Numerical simulations using the stochastic Landau-Lifshitz-Gilbert equation model the experimental observations in excellent agreement. These results represent an important contribution towards predicting viscosity effects and hence to maximise heat dissipation from magnetic nanoparticles regardless of the environment.

Nanoclusters of crystallographically aligned nanoparticles for magnetic thermotherapy: aqueous ferrofluid, agarose phantoms andex vivomelanoma tumour assessment

“…Our experiment only sense the ex vivo heating arising from the NCs distributed in tumour tissue as result from its interaction with living tissue. Results indicate a suppression of magnetic material effective heating efficiency which is not due to a change in viscosity and Brown mechanism inhibitions nor to aggregation phenomena inside endosomes as proposed in cell cultures 20,29,59 . As it was previously demonstrated in cancer cell cultures 23,24,26,27 we hypothesized that the irregular distribution of NC inside an heterogeneous tumour generates hot spots that are responsible for a local heating but no for a global temperature increase.…”

Dynamical Magnetic Response of Iron Oxide Nanoparticles Inside Live Cells

“…These different SAR values depending on particle size can be understood in terms of IONP volume (V), 9 or in other words: different magnetic anisotropy energy barrier KV, where K is the magnetic anisotropy. 38 In order to assess the dynamical magnetic response in live cells, we incubated IONPs with a breast cancer cell line (MCF-7), following a standard cell culture protocol 41 IONPs, respectively ( Fig. S1 f, g).…”

Interplay of cell death signaling pathways mediated by alternating magnetic field gradient

“…In addition, MNPs with engineered magnetic properties and high biocompatibility have been shown to be a promising candidate for cancer treatment. A well-established method for treating cancerous tumors is magnetic hyperthermia, which uses localized heat generation by the interaction of the MNPs in a high-frequency alternating magnetic field, to trigger cancer cell apoptosis and tumor regression 7 – 10 . The magnetic hysteresis of the MNPs result in energy dissipated as thermal energy that induces a rise in temperature to a range of 41‒43 °C.…”