Size-Dependent Mechanisms in AC Magnetic Hyperthermia Response of Iron-Oxide Nanoparticles

Graphene/cobalt nanocarrier for hyperthermia therapy and MRI diagnosis

“…Brownian relaxation is the mechanical rotation of the nanocomposites in the suspention, and hystersis loss is the movement of domain walls while the NPs are multidomain [17][18][19][20][21]31]. While graphene/cobalt nanocomposites disperse in aqueous media, minor contribution comes from Brownian loss and the thermal activity is mainly correspondant to the Neel loss [20][21][22][23][24][25]. In addition, as the cobalt NPs are ferromagnetic in nature, there is also contribution in the thermal activity from the hystresis loss [31,25].…”

“…Based on relaxation losses of magnetic nanomaterials in alternating magnetic fields, MFH is employed as a non-invasive way for thermal ablation of deep tumor tissues at temperatures 5-7 o C higher than body temperature [17][18][19][20][21][22][23][24][25]. The application of hyperthermia therapy was first introduced in 1993 by Jordan [18].…”

Computational study on superparamagnetic hyperthermia with biocompatible SPIONs to destroy the cancer cells

“…The results for Fe 3 O 4 -CDs are shown in figure 3 for two values of the magnetic field, considering biological accessibility limit, Hf  5×10 9 Am -1 Hz [7]. In this case, two magnetic relaxation processes contribute to the SAR, both Néel and Brown, for magnetic diameters greater than 15 nm.…”

“…The study focused on finding the optimum diameter of the nanoparticles, which is a critical parameter, and on the way in which the thickness of the biological membrane of the Ls and of the layer determined by the CDs at the surface of the biocompatible nanoparticles, when dispersed in water, influence the contribution of the Neel-Brown relaxation processes in obtaining the maximum SAR. Furthermore, for this study, we took into consideration a very small volume fraction of the nanoparticles, of only 1.7 vol%, which allows the maintenance of the superparamagnetic behavior of nanoparticles [8], without the appearance of the hysteresis loop caused by the interactions between nanoparticles [9], and the application of the Neel-Brown relaxation theory; in static conditions (where the measuring time is ~100 s [10]), in the lack of the interactions between nanoparticles, and as a result of the reduced magnetic anisotropy of the Fe 3 O 4 and -Fe 2 O 3 nanoparticles, the superparamagnetic (SPM) behavior is maintained for rather large diameters (<20 nm), because the Neel-Brown relaxation times (in the order of nano -microseconds) are much lower than the measuring time (tens -hundreds of seconds). Consequently, considering the Neel-Brown magnetic relaxation, we aimed to find the optimum conditions in which the highest maximum SAR is obtained for the nanoparticles of Fe 3 O 4 and -Fe 2 O 3 , when they are encapsulated in Ls or bioconjugated with CDs, without exceeding the biological limit [7].…”

A lock-in-based method to examine the thermal signatures of magnetic nanoparticles in the liquid, solid and aggregated states

“…However, it was shown as well how quickly this situation may deteriorate if the materials are compromised, i.e., if they aggregate. While the consequences of this phenomenon on the heating power, although previously addressed, 14,42,[49][50][51][52][53][54][55] are still not fully understood, they relate to the basic contributions between relaxation mechanisms. With these SPIONs, Néel relaxation seemed to be the dominating relaxation mechanism.…”