Nanoparticle-mediated magnetic hyperthermia in the treatment of neurological disorders.

Targeted nanoscale magnetic hyperthermia: challenges and potentials of peptide-based targeting.

Magnetic hyperthermia (MHT) is an oncological therapy that uses magnetic nanoparticles (MNPs) to generate localized heat under a low-frequency alternating magnetic field (AMF). Recently, trapezoidal pulsed alternating magnetic fields (TPAMFs) have proven their efficacy in enhancing the efficiency of heating in MHT as compared to the sinusoidal one. Our study aims to compare the TPAMF waveform's killing effect against the sinusoidal waveform in B16F10 and CT2A cell lines to determine more efficient waveforms in causing cell death. For that purpose, we used MNPs and different AMF waveforms: trapezoidal (TP), almost-square (TS), triangular (TR), and sinusoidal signal (SN). MNPs at 1 and 4 mg/mL did not affect cell viability during treatment. The exposition of B16F10 and CT2A cells to only AMF showed nonsignificant mortality. Hence, the synergetic effect of the AMF and MNPs causes the observed cell death. Among the explored cases, the nonharmonic signals demonstrated better efficacy than the SN one as an MHT treatment. This study has revealed that the application of TP, TS, or TR waveforms is more efficient and has considerable capability to increase cancer cell death compared to the traditional sinusoidal treatment. Overall, we can conclude that the application of nonharmonic signals enhances MHT treatment efficiency against tumor cells.

Background: Magnetic drug targeting (MDT) uses magnetic fields to localize magnetic nanoparticles (MNP) to tumor. Once localized, applying an alternating magnetic field (AMF) to the MNPs generates heat energy. Poly-N-isopropylacrylamide (PNIPA) is a thermosensitive polymer that contracts when heated, releasing any drugs which are bound to it. Utilizing these properties, MNP coated with PNIPA polymer on to which doxorubicin is loaded can be localized to hepatocellular carcinoma (HCC) with an external magnetic field. Application of an AMF will then generate localized magnetic hyperthermia (MH) within the tumor, thus releasing bound doxorubicin. This study explores this novel drug delivery model which can be used for targeted dual therapy (MDT and MH) of HCC. Aim: To demonstrate that doxorubicin-loaded-PNIPA-coated-MNP can be delivered intra-arterially to target HCC in a rat model and that heat is generated and doxorubicin is released when an AMF is applied. Methods: Morris hepatoma cells are implanted into the livers of buffalo rats. HCC development is confirmed on MRI using a specially-constructed rat-MRI coil. 0.5 ml of doxorubicin-loaded-PNIPA-coated-MNP solution is injected into the hepatic artery and localization of MNP in HCC is confirmed with MRI. Rats are sacrificed for histology of liver and other organs. AMF is applied to doxorubicin-loaded-PNIPA-coated-MNP solution and the temperature measured to demonstrate local hyperthermia in vitro. The amount of doxorubicin released is measured by spectrophotometry. Results: Successful intra-arterial delivery of MNP was confirmed on post-injection MRI. On histology, iron particles were seen in HCC but not in normal liver or other organs. When AMF was applied, temperature of the suspension reached the target temperature of 42°C within 5 minutes and remained within hyperthermia range(42°C-48°C) for 15 minutes. During this period of hyperthermia, 4.7% (~71 μg) of loaded doxorubicin was released. Conclusions: We have demonstrated in a rat model the feasibility of intra-arterial doxorubicin-loaded-PNIPA-coated-MNP for synergistic dual therapy of HCC using targeted hyperthermia and doxorubicin.

The principle of magnetic hyperthermia is to generate localized heating on target proteins, cells and tissue that are targeted by magnetic nanoparticles (MNPs) upon stimulation by remotely applied high frequency alternating magnetic field (AMF). Beyond its traditional applications in hyperthermia therapy, recent studies demonstrated the feasibility of magnetic hyperthermia as a new strategy for neural stimulation. The objective of this study is to examine the feasibility of localized magnetic hyperthermia (i.e. MNP/AMF hyperthermia) as a new strategy for brain stimulation, especially in modulating microglia activity and behaviors in vivo. This was examined by correlating a varying degree of MNP/AMF-induced thermal dose with the extent of microglial activation in the mouse brain. The MNP/AMF hyperthermia stimulation applied at a mild thermal dose to the mouse hippocampus significantly increased the infiltration of microglia and altered their morphology towards reactive and ameboid-like phenotypes in a thermal dose-dependent manner. Importantly, these responses were associated with increased expression of heat shock protein 70 (HSP70), a molecular chaperon protein, and LC3II, a marker of autophagic activity. Our findings support the feasibility of developing mild magnetic hyperthermia as a new strategy for localized stimulation of brain tissue.

Background: Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor in humans. In spite of advances in treatment strategies, survival rate of GBM remains poor. We have recently reported a novel anti-cancer compound with intrinsic magnetism(EI236). In addition to its anti-cancer effect, EI236 generates a large amount of heat upon an alternating magnetic field (AMF) application because of its magnetism, i.e., hyperthermic effect. In this study, we have examined the effect of EI236 on human GBM in vitroand vivo. Materials and Methods: Human GBM cell lines, U251MG, YKG-1, and U87, were used in this study. Cell proliferation was assessed by methyl thiazolyl tetrazorium (MTT) assays in the presence of EI236, in comparison to temozolomide (TMZ) and calmustine (BCNU), i.e. the clinical standard drugs for GBM. Apoptosis was analyzed by fluorescence activated cells sorting. In addition, we have examined whether EI236 inhibited the tumor growth with/without AMF application in animal models. Tumors were induced by implantation of U251MG cells into the hip of female Balb-c mice. Seven days after the implantation of GBM cells, EI236, BCNU or normal saline (control) was injected respectively into the tumors and mice were exposed to an AMF application(330.8A, 280kHz) for 30 minutes. Therefore, we calculated the tumor volume and the regression rate of tumors twice a week. Result: EI236 inhibited the proliferation of all cell lines and increased apoptosis in a dose dependent manner. Moreover, we found that EI236 had much greater anti-cancer effect than the clinical standard drugs. Mice bearing GBM cancer cells in their hip were then subjected to a double combination therapy, consisting of local injection of EI236 and hyperthermic treatment by AMF application. Tumor sizes in both drug stimulation groups were reduced, especially that in EI236 with AMF application group was highly reduced, while that in control group was increased. Conclusion: EI236 has greater anti-cancer effect than TMZ and BCNU, i.e. the clinical standard drugs. Besides this strong anti-cancer effect, EI236 has hyperthermic effect upon an AMF application because of heat generation. Accordingly, EI236 may enable us to develop novel strategies in GBM treatment, i.e. hyperthermic-chemotherapy with a single-drug compound. Note: This abstract was not presented at the meeting. Citation Format: Makoto Ohtake, Masanari Umemura, Itaru Sato, Kayoko Oda, Akane Nagasako, Ayako Makino, Haruki Aoyama, Mayumi Katsumata, Haruki Eguchi, Nobutaka Kawahara, Yoshihiro Ishikawa. Simultaneous hyperthermic-chemotherapy for glioblastoma using a single anti-cancer compound with intrinsic magnetism. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4548. doi:10.1158/1538-7445.AM2015-4548

Prostate cancer is the leading cause of cancer death in American men. The high mortality rate is attributable to current treatments not providing a cure for hormone-refractory prostate cancer. The main goal of this project is to provide a novel therapeutic approach based on nanoparticle-mediated magnetic hyperthermia for efficient treatment of this cancer. Magnetic hyperthermia is a form of thermal therapy where magnetic nanoparticles delivered to cancer sites generate heat after exposure to an external alternating magnetic field (AMF). Many studies suggest that it has significant potential to kill cancer cells directly or enhance their susceptibility to radiation, chemotherapy and immunotherapy. Magnetic hyperthermia, however, is restricted to the treatment of localized and accessible tumors because therapeutic temperatures above 40 Celsius have only been achieved by intratumoral injection of magnetic nanoparticles. This is due to the low heating efficiency of conventional iron oxide nanoparticles combined with low tumor accumulation of these nanoparticles following systemic delivery. To employ this therapy for primary and metastatic prostate cancer tumors that are difficult to access for intratumoral injection, we have designed novel biocompatible nanoclusters with high heating efficiency that efficiently accumulate in prostate cancer tumors after intravenous injection at clinically relevant doses and generate the desirable intratumoral temperatures upon exposure to AMF. Our nanoclusters are built on hydrophobic iron oxide nanoparticles doped with zinc and manganese. To overcome challenges associated with poor water solubility of the synthesized nanoparticles, the solvent evaporation approach was employed to encapsulate and cluster them within the hydrophobic core of PEG-PCL-based polymeric nanoparticles. The amphiphilic PEG-PCL (methoxy poly(ethylene glycol)-b-poly(ϵ-caprolactone)) molecules, composed of hydrophobic 10 kDa PCL and hydrophilic 5 kDa PEG blocks, self-assemble in aqueous solution upon evaporation of the organic solvent to form nanoparticles with a hydrophilic PEG outer shell and hydrophobic PCL core. The transmission electron microscope images reveal that iron oxide nanoparticles form clusters within a single PEG-PCL nanoparticle. It is validated that the clustering of iron oxide nanoparticles enhances their heating efficiency. Animal studies demonstrate that following intravenous injection into mice bearing prostate cancer grafts the nanoclusters efficiently accumulate in cancer tumors and increase the intratumoral temperature up to 42 Celsius upon exposure to AMF. Finally, the systemically delivered magnetic hyperthermia significantly inhibits prostate cancer growth and does not exhibit any sign of toxicity. In summary, this discovery will allow to realize the true therapeutic potential of magnetic hyperthermia alone and in combination with other therapies for inaccessible primary and metastatic prostate cancer tumors. Citation Format: Oleh Taratula, Olena Taratula. Intravascular delivery of nanoclusters for treatment of prostate cancer with magnetic hyperthermia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2875.

Magnetic hyperthermia (MHT), which combines magnetic nanoparticles (MNPs) with an alternating magnetic field (AMF), holds promise as a cancer therapy. There have been many studies about hyperthermia, most of which have been performed by direct injection of MNPs into tumor tissues. However, there have been no reports of treating peritoneal disseminated disease with MHT to date. In the present study, we treated peritoneal metastasis of gastric cancer with MHT using superparamagnetic iron oxide (Fe3O4) nanoparticle (SPION) coated with carboxydextran as an MNP, in an orthotopic mouse model mimicking early peritoneal disseminated disease of gastric cancer. SPIONs of an optimal size were intraperitoneally administered, and an AMF (390 kHz, 28 kAm−1) was applied for 10 minutes, four times every three days. Three weeks after the first MHT treatment, the peritoneal metastases were significantly inhibited compared with the AMF-alone group or the untreated-control group. The results of the present study show that MHT can be applied as a new treatment option for disseminated peritoneal gastric cancer. Abbreviations: AMF: alternating magnetic field; Cy1: cytology-positive; DMEM: Dulbecco’s Modified Eagle’s Medium; FBS: fetal bovine serum; H&E: hematoxylin and eosin; HIPEC: hyperthermic intraperitoneal chemotherapy; MEM: Minimum Essential Medium; MHT: magnetic hyperthermia; MNPs: magnetic nanoparticles; P0: macroscopic peritoneal dissemination; RFP: red fluorescent protein; SPION: superparamagnetic iron oxide (Fe3O4) nanoparticle

Hyperthermia has been used for cancer therapy for a long period of time, but has shown limited clinical efficacy. Induction-heating hyperthermia using the combination of magnetic nanoparticles (MNPs) and an alternating magnetic field (AMF), termed magnetic hyperthermia (MHT), has previously shown efficacy in an orthotopic mouse model of disseminated gastric cancer. In the present study, superparamagnetic iron oxide nanoparticles (SPIONs), a type of MNP, were conjugated with an anti-HER2 antibody, trastuzumab and termed anti-HER2-antibody-linked SPION nanoparticles (anti-HER2 SPIONs). Anti-HER2 SPIONs selectively targeted HER2-expressing cancer cells co-cultured along with normal fibroblasts and HER2-negative cancer cells and caused apoptosis only in the HER2-expressing individual cancer cells. The results of the present study show proof-of-concept of a novel hyperthermia technology, immuno-MHT for selective cancer therapy, that targets individual cancer cells. Abbreviations: AMF: alternating magnetic field; DDW: double distilled water; DMEM: Dulbecco’s Modified Eagle’s; Medium; f: frequency; FBS: fetal bovine serum; FITC: Fluorescein isothiocyanate; GFP: green fluorescent protein; H: amplitude; Hsp: heat shock protein; MHT: magnetic hyperthermia; MNPs: magnetic nanoparticles; PI: propidium iodide; RFP: red fluorescent protein; SPION: superparamagnetic iron oxide (Fe3O4) nanoparticle.

Magnetic nanoparticle-mediated hyperthermia (MNHT) can heat tumor tissue to the desired temperature without damaging surrounding normal tissue. The MNHT system consists of targeting tumor with functional magnetic nanoparticles (MNPs) and then applying an external alternating magnetic field (AMF) to generate heat in the MNPs. Temperature in the tumor tissue is increased to above 43 °C, which causes necrosis of cancer cells but does not damage surrounding normal tissue. Among available MNPs, magnetite has been extensively studied. Recent years have seen remarkable advances in MNHT; both functional MNPs and AMF generators have been developed. By applying MNHT, heat shock proteins (HSPs) are highly expressed within and around tumor tissue, which causes intriguing biological responses such as tumor-specific immune response. These results suggest that MNHT is able to kill not only tumors exposed to heat treatment, but also unheated metastatic tumors at distant sites. Currently, some researchers have started clinical trials, suggesting that the time has come for clinical applications.

Purpose Magnetic particle hyperthermia is an approved cancer treatment that harnesses thermal energy generated by magnetic nanoparticles when they are exposed to an alternating magnetic field (AMF). Thermal stress is either directly cytotoxic or increases the susceptibility of cancer cells to standard therapies, such as radiation. As with other thermal therapies, the challenge with nanoparticle hyperthermia is controlling energy delivery. Here, we describe the design and implementation of a prototype pre-clinical device, called HYPER, that achieves spatially confined nanoparticle heating within a user-selected volume and location. Design Spatial control of nanoparticle heating was achieved by placing an AMF generating coil (340 kHz, 0–15 mT), between two opposing permanent magnets. The relative positions between the magnets determined the magnetic field gradient (0.7 T/m–2.3 T/m), which in turn governed the volume of the field free region (FFR) between them (0.8–35 cm3). Both the gradient value and position of the FFR within the AMF ([−14, 14]x, [−18, 18]y, [−30, 30]z) mm are values selected by the user via the graphical user interface (GUI). The software then controls linear actuators that move the static magnets to adjust the position of the FFR in 3D space based on user input. Within the FFR, the nanoparticles generate hysteresis heating; however, outside the FFR where the static field is non-negligible, the nanoparticles are unable to generate hysteresis loss power. Verification We verified the performance of the HYPER to design specifications by independently heating two nanoparticle-rich areas of a phantom placed within the volume occupied by the AMF heating coil.

Our purpose in this study was to present three methods for estimating specific loss power (SLP) in magnetic hyperthermia with use of an alternating magnetic field (AMF) and magnetic nanoparticles (MNPs) and to compare the SLP values estimated by the three methods using simulation studies under various diameters of MNPs (D), amplitudes (H0) and frequencies of AMF (f). In the first method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically (SLP1). In the second method, the SLP was obtained by solving Shliomis’ relaxation equation using the complex susceptibility (SLP2). The third method was based on Rosensweig’s model (SLP3). The SLP3 value changed largely depending on the magnetic field strength (H) in the Langevin parameter (§) and it became maximum (SLP3max) and minimum (SLP3min) when H was 0 and ±H0, respectively. The relative difference between SLP1 and SLP2 was the largest and increased with increasing D and H0, whereas that between SLP1 and was the smallest and was almost constant regardless of D and H0, suggesting that H in ξ should be taken as H0 in estimating the SLP using Rosensweig’s model. In conclusion, this study will be useful for optimizing the parameters of AMF in magnetic hyperthermia and for the optimal design of MNPs for magnetic hyperthermia.

Simple SummaryA novel human-sized alternating magnetic field (AMF) coil is researched, designed and evaluated using numerical methods to achieve magnetic nanoparticle hyperthermia therapy in deep-seated tumors while avoiding damage to normal tissues. This is achieved by utilizing a circular current’s electric and magnetic field spatial distributions. The studies are done for pancreatic cancer. Computational electromagnetic and temperature distributions are presented for a full-body, 3D human model. The results showed that the proposed human-sized coil could provide clinically relevant AMF to cancerous regions while causing negligible Joule heating to normal tissue, compared to commonly used AMF coils.Magnetic nanoparticle (MNP) hyperthermia therapy is a treatment technique that can be used alone or as an adjunct to radiation and/or chemotherapies for killing cancer cells. During treatment, MNPs absorb a part of electromagnetic field (EMF) energy and generate localized heat when subjected to an alternating magnetic field (AMF). The MNP-absorbed EMF energy, which is characterized by a specific absorption rate (SAR), is directly proportional to AMF frequency and the magnitude of transmitting currents in the coil. Furthermore, the AMF penetrates inside tissue and induces eddy currents in electrically conducting tissues, which are proportional to the electric field (J = σE). The eddy currents produce Joule heating (<J·E> = 0.5·σ·E2) in the normal tissue, the rate of energy transfer to the charge carriers from the applied electric fields. This Joule heating contains only the electric field because the magnetic field is always perpendicular to the velocity of the conduction charges, i.e., it does not produce work on moving charge. Like the SAR due to MNP, the electric field produced by the AMF coil is directly proportional to AMF frequency and the magnitude of transmitting currents in the coil. As a result, the Joule heating is directly proportional to the square of the frequency and transmitter current magnitude. Due to the fast decay of magnetic fields from an AMF coil over distance, MNP hyperthermia treatment of deep-seated tumors requires high-magnitude transmitting currents in the coil for clinically achievable MNP distributions in the tumor. This inevitably produces significant Joule heating in the normal tissue and becomes more complicated for a standard MNP hyperthermia approach for deep-seated tumors, such as pancreatic, prostate, liver, lung, ovarian, kidney, and colorectal cancers. This paper presents a novel human-sized AMF coil and MNP hyperthermia system design for safely and effectively treating deep-seated cancers. The proposed design utilizes the spatial distribution of electric and magnetic fields of circular coils. Namely, it first minimizes the SAR due to eddy currents in the normal tissue by moving the conductors away from the tissue (i.e., increasing coils’ radii), and second, it increases the magnetic field at the targeted area (z = 0) due to elevated coils (|z| > 0) by increasing the radius of the elevated coils (|z| > 0). This approach is a promising alternative aimed at overcoming the limitation of standard MNP hyperthermia for deep-seated cancers by taking advantage of the transmitter coil’s electric and magnetic field distributions in the human body for maximizing AMF in tumor regions and avoiding damage to normal tissue. The human-sized coil’s AMF, MNP activation, and eddy current distribution characteristics are investigated for safe and effective treatment of deep-seated tumors using numerical models. Namely, computational results such as AMF, Joule heating SAR, and temperature distributions are presented for a full-body, 3D human model. The SAR and temperature distributions clearly show that the proposed human-sized AMF coil can provide clinically relevant AMF to the region occupied by deep-seated cancers for the application of MNP hyperthermia therapy while causing less Joule heating in the normal tissues than commonly used AMF techniques.

Magnetically responsive peptide coacervates for dual hyperthermia and chemotherapy treatments of liver cancer

Alternating magnetic field (AMF) configurable at a range of frequencies is a critical need for optimization of magnetic nanoparticle based hyperthermia, and for their application in targeted drug delivery. Currently, most commercial AMF devices including induction heaters operate at one factory-fixed frequency, thereby limiting customized frequency configuration required for triggered drug release at mild hyperthermia (40-42&deg;C) and ablations (&gt;55&deg;C). Most AMF devices run as an inductor-capacitor resonance network that could allow AMF frequencies to be changed by changing the capacitor bank or the coil looped with it. When developing AMF inhouse, the most expensive component is usually the RF power amplifier, and arguably the most critical step of building a strong AMF field is impedance-matched coupling of RF power to the coolant-cooled AMF coil. AMF devices running at 10KA/m strength are quite common, but generating AMF at that level of field strength using RF power less than 1KW has remained challenging. We practiced a few techniques for building 10KA/m AMFs at different frequencies, by utilizing a 0.5KW 80-800KHz RF power amplifier. Among the techniques indispensable to the functioning of these AMFs, a simple cost-effective technique was the tapping methods for discretely or continuously adjusting the position of an RF-input-tap on a single-layer or the outer-layer of a multi-layer AMF coil for maximum power coupling into the AMF coil. These in-house techniques when combined facilitated 10KA/m AMF at frequencies of 88.8 KHz and higher as allowed by the inventory of capacitors using 0.5KW RF power, for testing heating of 10-15nm size magnetic particles and on-going evaluation of drug-release by low-level temperature-sensitive liposomes loaded with 15nm magnetic nanoparticles.

Magnetic drug carriers: bright insights from light-responsive magnetic liposomes.