Simulation and experimental studies on magnetic hyperthermia with use of superparamagnetic iron oxide nanoparticles

Physical mechanism and modeling of heat generation and transfer in magnetic fluid hyperthermia through Néelian and Brownian relaxation: a review

Current clinically accepted technologies for cancer treatment still have limitations which lead to the exploration of new therapeutic methods. Since the past few decades, the hyperthermia treatment has attracted the attention of investigators owing to its strong biological rationales in applying hyperthermia as a cancer treatment modality. Advancement of nanotechnology offers a potential new heating method for hyperthermia by using nanoparticles which is termed as magnetic fluid hyperthermia (MFH). In MFH, superparamagnetic nanoparticles dissipate heat through Néelian and Brownian relaxation in the presence of an alternating magnetic field. The heating power of these particles is dependent on particle properties and treatment settings. A number of pre-clinical and clinical trials were performed to test the feasibility of this novel treatment modality. There are still issues yet to be solved for the successful transition of this technology from bench to bedside. These issues include the planning, execution, monitoring and optimization of treatment. The modeling and simulation play crucial roles in solving some of these issues. Thus, this review paper provides a basic understanding of the fundamental and rationales of hyperthermia and recent development in the modeling and simulation applied to depict the heat generation and transfer phenomena in the MFH.

Determining iron oxide nanoparticle heating efficiency and elucidating local nanoparticle temperature for application in agarose gel-based tumor model

Magnetic iron oxide nanoparticles (MNPs) have been developed for magnetic fluid hyperthermia (MFH) cancer therapy, where cancer cells are treated through the heat generated by application of a high frequency magnetic field. This heat has also been proposed as a mechanism to trigger release of chemotherapy agents. In each of these cases, MNPs with optimal heating performance can be used to maximize therapeutic effect while minimizing the required dosage of MNPs. In this study, the heating efficiencies (or specific absorption rate, SAR) of two types of MNPs were evaluated experimentally and then predicted from their magnetic properties. MNPs were also incorporated in the core of poly(ethylene glycol-b-caprolactone) micelles, co-localized with rhodamine B fluorescent dye attached to polycaprolactone to monitor local, nanoscale temperatures during magnetic heating. Despite a relatively high SAR produced by these MNPs, no significant temperature rise beyond that observed in the bulk solution was measured by fluorescence in the core of the magnetic micelles. MNPs were also incorporated into a macro-scale agarose gel system that mimicked a tumor targeted by MNPs and surrounded by healthy tissues. The agarose-based tumor models showed that targeted MNPs can reach hyperthermia temperatures inside a tumor with a sufficient MNP concentration, while causing minimal temperature rise in the healthy tissue surrounding the tumor.

Impact of magnetic field parameters and iron oxide nanoparticle properties on heat generation for use in magnetic hyperthermia

Heating of nanoparticles (NPs) using an AC magnetic field depends on several factors, and optimization of these parameters can improve the efficiency of heat generation for effective cancer therapy while administering a low NP treatment dose. This study investigated magnetic field strength and frequency, NP size, NP concentration, and solution viscosity as important parameters that impact the heating efficiency of iron oxide NPs with magnetite (Fe3O4) and maghemite (γ-Fe2O3) crystal structures. Heating efficiencies were determined for each experimental setting, with specific absorption rates (SARs) ranging from 3.7 to 325.9 W/g Fe. Magnetic heating was conducted on iron oxide NPs synthesized in our laboratories (with average core sizes of 8, 11, 13, and 18 nm), as well as commercially-available iron oxides (with average core sizes of 8, 9, and 16 nm). The experimental magnetic coil system made it possible to isolate the effect of magnetic field parameters and independently study the effect on heat generation. The highest SAR values were found for the 18 nm synthesized particles and the maghemite nanopowder. Magnetic field strengths were applied in the range of 15.1 to 47.7 kA/m, with field frequencies ranging from 123 to 430 kHz. The best heating was observed for the highest field strengths and frequencies tested, with results following trends predicted by the Rosensweig equation. An increase in solution viscosity led to lower heating rates in nanoparticle solutions, which can have significant implications for the application of magnetic fluid hyperthermia in vivo.

In vivo monitoring of rat macrophages labeled with poly(l-lysine)-iron oxide nanoparticles

Coprecipitation of FeCl2 and FeCl3 with aqueous ammonia was used to prepare iron oxide nanoparticles dispersible in aqueous medium. Oxidation of the particles with sodium hypochlorite then yielded maghemite (γ-Fe2 O3 ) nanoparticles which were coated with two types of coating -d-mannose or poly(l-lysine) (PLL) as confirmed by FTIR analysis. The particles were <10 nm according to transmission electron microscopy. Their hydrodynamic particle size was ∼180 nm (by dynamic light scattering). The d-mannose-, PLL-coated, and neat γ-Fe2 O3 particles as well as commercial Resovist® were used to label rat macrophages. The viability and contrast properties of labeled macrophages were compared. PLL-coated γ-Fe2 O3 nanoparticles were found optimal. The labeled macrophages were injected to rats monitored in vivo by magnetic resonance imaging up to 48 h. Transport of macrophages labeled with PLL-γ-Fe2 O3 nanoparticles in rats was confirmed. Tracking of macrophages using the developed particles can be used for monitoring of inflammations and cell migration in cell therapy.

Hyperthermia generated with ferucarbotran (Resovist®) in an alternating magnetic field enhances cisplatin-induced apoptosis of cultured human oral cancer cells

Hyperthermia is a promising anti-cancer treatment in which the tissue temperature is increased to 42-45 °C, and which is often used in combination with chemotherapy or radiation therapy. Our aim in the present work was to examine the feasibility of combination therapy for oral cancer with cisplatin and hyperthermia generated with ferucarbotran (Resovist(®); superparamagnetic iron oxide) in an alternating magnetic field (AMF). First, we established that administration of ferucarbotran at the approved dosage for magnetic resonance imaging provides an iron concentration sufficient to increase the temperature to 42.5 °C upon exposure to AMF. Then, we examined the effect of cisplatin combined with ferucarbotran/AMF-induced hyperthermia on cultured human oral cancer cells (HSC-3 and OSC-19). Cisplatin alone induced apoptosis of cancer cells in a dose-dependent manner, as is well known. However, the combination of cisplatin with ferucarbotran/AMF was significantly more effective than cisplatin alone. This result suggests that it might be possible to reduce the clinically effective dosage of cisplatin by administering it in combination with ferucarbotran/AMF-induced hyperthermia, thereby potentially reducing the incidence of serious cisplatin-related side effects. Further work seems justified to evaluate simultaneous thermo-chemotherapy as a new approach to anticancer therapy.

The migration of synthetic magnetic nanoparticle labeled dendritic cells into lymph nodes with optical imaging

Background

The successful biotherapy of carcinoma with dendritic cell (DC) vaccines pivotally relies on DCs’ migratory capability into lymph tissues and activation of T cells. Accurate imaging and evaluation of DC migration in vivo have great significance during antitumor treatment with DC vaccine. We herein examined the behavior of DCs influenced by synthetic superparamagnetic iron oxide (SPIO) nanoparticle labeling.

Methods

γ-Fe₂O₃ nanoparticles were prepared and DCs, which were induced from bone marrow monocytes of enhanced green fluorescent protein (EGFP) transgenic mice, were labeled. The endocytosis of the SPIO, surface molecules, cell apoptosis and fluorescence intensity of EGFP-DCs were displayed by Prussian blue staining and flow cytometry (FCM), respectively. After EGFP-DCs, labeled with SPIO, were injected into footpads (n = 5) for 24 hours, the mice were examined in vivo by optical imaging (OPI). Meanwhile, confocal imaging and FCM were applied, respectively, to detect the migration of labeled DCs into draining lymph nodes.

Results

Nearly 100% of cells were labeled by the SPIO, in which the intracellular blue color gradually deepened and the iron contents rose with the increase of labeling iron concentrations. In addition, cell apoptosis and the surface molecules on DCs were at similar levels after SPIO labeling. After confirming that the fluorescence intensity of EGFP on DCs was not influenced by SPIO, the homing ability of EGFP-DCs labeled with SPIO displayed that the fluorescence intensity and the ratios of EGFP-DCs in draining lymph nodes were gradually decreased with the increase of labeling iron concentrations.

Conclusion

The synthetic SPIO nanoparticles possess perfect labeling ability and biocompatibility. Moreover, DCs labeled with a low dose of SPIO showed stronger migratory capability in vivo.

Simple and rapid synthesis of magnetite/hydroxyapatite composites for hyperthermia treatments via a mechanochemical route

This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments.

Antitumor effects of inductive hyperthermia using magnetic ferucarbotran nanoparticles on human lung cancer xenografts in nude mice

BACKGROUND

The effects of inductive hyperthermia on lung cancer have yet to be fully investigated. Magnetic nanoparticles used in inductive hyperthermia are made-to-order and expensive. This study was performed to investigate the use of ferucarbotran in inductive hyperthermia and to clarify whether inductive hyperthermia using ferucarbotran promotes antitumor effects in vivo using a lung cancer cell line.

METHODS

We injected A549 cells subcutaneously into the right thighs of BALB/c nu/nu nude mice. Forty mice with A549 xenografts were then classified into three groups. Group 1 was the control group. All mice in groups 2 and 3 had ferucarbotran injected into their tumors, and mice in group 3 were then subjected to alternating magnetic field irradiation. We evaluated tumor temperature during the hyperthermic procedure, the time course of tumor growth, histologic findings in tumors after hyperthermic treatment, and adverse events.

RESULTS

Intratumor temperature rose rapidly and was maintained at 43°C-45°C for 20 minutes in an alternating magnetic field. Tumor volumes in groups 1 and 2 increased exponentially, but tumor growth in group 3 was significantly suppressed. No severe adverse events were observed. Histologic findings for the tumors in group 3 revealed mainly necrosis.

CONCLUSION

Inductive hyperthermia using ferucarbotran is a beneficial and promising approach in the treatment of lung cancer. Ferucarbotran is a novel tool for further development of inductive hyperthermia.

Impact of surface coating and particle size on the uptake of small and ultrasmall superparamagnetic iron oxide nanoparticles by macrophages

PURPOSE

Magnetic resonance imaging (MRI) using contrast agents like superparamagnetic iron oxide (SPIO) is an extremely versatile technique to diagnose diseases and to monitor treatment. This study tested the relative importance of particle size and surface coating for the optimization of MRI contrast and labeling efficiency of macrophages migrating to remote inflammation sites.

MATERIALS AND METHODS

We tested four SPIO and ultrasmall superparamagnetic iron oxide (USPIO), alkali-treated dextran magnetite (ATDM) with particle sizes of 28 and 74 nm, and carboxymethyl dextran magnetite (CMDM) with particle sizes of 28 and 72 nm. Mouse macrophage RAW264 cells were incubated with SPIOs and USPIOs, and the labeling efficiency of the cells was determined by the percentage of Berlin blue-stained cells and by measuring T(2) relaxation times with 11.7-T MRI. We used trypan blue staining to measure cell viability.

RESULTS

Analysis of the properties of the nanoparticles revealed that ATDM-coated 74 nm particles have a lower T(2) relaxation time than the others, translating into a higher ability of MRI negative contrast agent. Among the other three candidates, CMDM-coated particles showed the highest T(2) relaxation time once internalized by macrophages. Regarding labeling efficiency, ATDM coating resulted in a cellular uptake higher than CMDM coating, independent of nanoparticle size. None of these particle formulations affected macrophage viability.

CONCLUSION

This study suggests that coating is more critical than size to optimize the SPIO labeling of macrophages. Among the formulations tested in this study, the best MRI contrast and labeling efficiency are expected with ATDM-coated 74 nm nanoparticles.

Control of the temperature rise in magnetic hyperthermia with use of an external static magnetic field

Our purpose in this study was to investigate the usefulness of a method for controlling the temperature rise in magnetic hyperthermia (MH) using an external static magnetic field (SMF), and to derive an empirical equation for describing the energy dissipation of magnetic nanoparticles (MNPs) in the presence of both the alternating magnetic field (AMF) and SMF through phantom experiments. We made a device that allows for MH in the presence of an SMF with a field-free point (FFP) using a Maxwell coil pair. We measured the temperature rise of MNPs under various conditions of AMF and SMF and various distances from the FFP (d), and calculated the specific absorption rate (SAR) from the initial slope of the temperature curve. The SAR values decreased with increasing strength of SMF (Hs) and d. The extent of their decrease with d increased with an increase of the gradient of SMF (Gs). The relationships between SAR and Hs and between SAR and d could be well approximated by Rosensweig's equation in which the amplitude of AMF (Hac) is replaced by √[Hac(2)]/√[Hac(2)+Hs(2)], except for the case when Gs was small. In conclusion, the use of an external SMF with an FFP will be effective for controlling the temperature rise in MH in order to reduce the risk of heating surrounding healthy tissues, and our empirical equation will be useful for estimating SAR in the presence of both the AMF and SMF and for designing an effective local heating system for MH.