Distinguishing between heating power and hyperthermic cell-treatment efficacy in magnetic fluid hyperthermia

Abstract

In the magnetic fluid hyperthermia (MFH) research field, it is usually assumed that achieving a uniform temperature enhancement (ΔT) of the entire tumour is a key-point for treatment. However, various experimental works reported successful cell apoptosis via MFH without a noticeable ΔT of the system. A possible explanation of the success of these negligible-ΔT experiments is that a local ΔT restricted to the particle nanoenvironment (i.e. with no significant effect on the global temperature T) could be enough to trigger cell death. Shedding light on such a possibility requires accurate knowledge of heat dissipation at the local level in relation to the usually investigated global (average) one. Since size polydispersity is inherent to all synthesis techniques and the heat released is proportional to the particle size, heat dissipation spots with different performances - and thus different effects on the cells - will likely exist in every sample. In this work we aim for a double objective: (1) to emphasize the necessity to distinguish between the total dissipated heat and hyperthermia effectiveness, and (2) to suggest a theoretical approach on how to select, for a given size polydispersity, a more adequate average size so that most of the particles dissipate within a desired heating power range. The results are reported in terms of FeO nanoparticles as a representative example.

Comparative Study of Extracellular and Intracellular Magnetic Hyperthermia Treatments Using Magnetic Particle Imaging

“…These results raised some debate in the literature, because it has been usually thought that it is necessary to achieve a homogeneous increase in temperature within the tumor for effective hyperthermia [10]. As a possible explanation for the above results, it has been hypothesized that even an increase in temperature localized in the vicinity of the MNPs could be enough to induce cell death without a significant global increase in temperature [6] [7] [8] [9].…”

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

“…Composition modification comparing with iron oxides entails the problem of increasing cytotoxicity. Regarding to the effects related to the interaction between MNPs and biological entities, SAR values appear highly suppressed when MNPs are located in cells as described in various in vitro assays 20,[23][24][25][26][27] .The pioneering work of Fortin et al 20 related this attenuation to the inhibition of Brown contribution to heat generation, due to abrupt change in media viscosity. Also, significant reductions in cell viability without macroscopic cell cultures temperature rise has been reported for various cancer cells with MNPs internalised and exposed to AMF, like in Hella cells loaded with silica-coated manganese oxide 27 and in dendritic cells loaded with magnetite having either positive (NH+2 ) or negative (COOH−) surface functional groups 28 as well as in the case of nanoparticles engineered for targeted hyperthermia as CMD coated magnetite conjugated with epidermal growth factor (EGF) in MDA-MB-468 and MCF-7 cells 23,26 .…”

“…also expressed the EGFP after being loaded with magnetite MNPs and exposed to RF fields indicating that endocyted MNPs create hot spots inside the cells, even though the amount of heat released was not enough to globally increase the cell culture temperature 24 . The need of distinguishing between global heating and cell-treatment efficacy to improved hyperthermia treatment was later discussed elsewhere 25 . Other explanation referred to aggregation inside cell endosomes 29,30 .…”

Specific Loss Power in Magnetic Hyperthermia: Comparison of Monodispersion and Polydispersion

“…Because not all particles in a certain volume have the same diameter Din the polydisperse case [13], [14], the SLP qss value calculated from Eq. 13should be averaged based on the particle size distribution as…”

“…Furthermore, we have also presented a method for estimating the SLP in the presence of both the AMF and SMF [11], which was based on the numerical solution of the magnetization relaxation equation of Shliomis [12].In our previous papers [8], [11], however, the particle size distribution was assumed to be monodisperse. As pointed out by Munoz-Menendez et al [13], [14], the existence of some size polydispersity of MNPs is experimentally unavoidable, resulting in a different hyperthermia performance depending on the size of each MNP. Thus, the size polydispersity of MNPs is one of the important issues to achieve an accurate control of the heating performance of MNPs.…”