Apoptosis selectively induced in BEL-7402 cells by folic acid-modified magnetic nanoparticles combined with 100 Hz magnetic field

Progressive Study on the Non-thermal Effects of Magnetic Field Therapy in Oncology

Cancer is one of the most common causes of death worldwide. Although the existing therapies have made great progress and significantly improved the prognosis of patients, it is undeniable that these treatment measures still cause some serious side effects. In this context, a new treatment method is needed to address these shortcomings. In recent years, the magnetic fields have been proposed as a novel treatment method with the advantages of less side effects, high efficiency, wide applications, and low costs without forming scars. Previous studies reported that static magnetic fields (SMFs) and low-frequency magnetic fields (LF-MFs, frequency below 300 Hz) exert anti-tumor function, independent of thermal effects. Magnetic fields (MFs) could inhibit cell growth and proliferation; induce cell cycle arrest, apoptosis, autophagy, and differentiation; regulate the immune system; and suppress angiogenesis and metastasis via various signaling pathways. In addition, they are effective in combination therapies: MFs not only promote the absorption of chemotherapy drugs by producing small holes on the surface of cell membrane but also enhance the inhibitory effects by regulating apoptosis and cell cycle related proteins. At present, MFs can be used as drug delivery systems to target magnetic nanoparticles (MNPs) to tumors. This review aims to summarize and analyze the current knowledge of the pre-clinical studies of anti-tumor effects and their underlying mechanisms and discuss the prospects of the application of MF therapy in cancer prevention and treatment.

Iron oxide nanoparticles as nanocarriers to improve chlorin e6-based sonosensitivity in sonodynamic therapy

Background

Compared to the excitation light in photodynamic therapy, ultrasound in sonodynamic therapy (SDT) could easily penetrate into the deep tumor in liver. However, the photosensitizer chlorin e6 (E6) activated by ultrasound has been limited in its application in clinics for the poor water solubility of E6 and poor effect of SDT. Nanoparticles as cavitation promotors may be able to amplify the E6-mediated SDT effect and also improve its water solubility.

Objective

The objective of the study was to develop an E6-based sonosensitizer with improved SDT effect and good water solubility using nanotechnology.

Materials and methods

Polyethylene glycol (PEG)ylated iron oxide nanoparticles coated with E6 (PION@E6) was prepared by means of pyrolysis and phase transfer. Characterization of PION@E6 was performed by means of transmission electron microscopy, hydrate particle size analysis, and absorption and fluorescence spectra analysis. Uptake of PION@E6 by H22 cells (a murine hepatoma cell line) was measured by inductively coupled plasma atomic emission spectroscopy. The effect of SDT on H22 cells was studied by the combination of ultrasound treatment with PION@E6 incubation. Cell viability was measured using cell counting kit-8 assay. Cell apoptosis was analyzed by flow cytometry. ROS generation was measured using DCFH-DA (2',7'-dichlorodihydrofluorescein diacetate) probing kit.

Results

Absorption spectra of PION@E6 revealed successful loading of E6 onto the PIONs. It showed excellent water solubility and stability with a size of 37.86±12.90 nm in diameter. The fluorescence spectra of PION@E6 revealed a red-shift compared with free E6. When combined with ultrasound treatment, it showed a significantly better inhibitory effect on H22 cells and correspondingly higher level of intracellular ROS generation compared with free E6. Furthermore, either higher dose of PION@E6 or higher power intensity of ultrasound initiated significantly better SDT effect and correspondingly higher level of intracellular ROS generation compared with lower dose of PION@E6 or ultrasound, respectively.

Conclusion

PION@E6 is a superior potential sonosensitizer to E6 to treat tumors by SDT.

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We demonstrate that further research focusing on the accurate manipulation of the aforementioned magnetic field exposure parameters could lead to the development of successful non-invasive therapeutic anticancer approaches.

Targeted Magnetic Nanotheranostics of Cancer

Current advances in targeted magnetic nanotheranostics are summarized in this review. Unique structural, optical, electronic and thermal properties of magnetic materials in nanometer scale are attractive in the field of biomedicine. Magnetic nanoparticles functionalized with therapeutic molecules, ligands for targeted delivery, fluorescent and other chemical agents can be used for cancer diagnostic and therapeutic purposes. High selectivity, small size, and low immunogenicity of synthetic nucleic acid aptamers make them attractive delivery agents for therapeutic purposes. Properties, production and functionalization of magnetic nanoparticles and aptamers as ligands for targeted delivery are discussed herein. In recent years, magnetic nanoparticles have been widely used in diagnostic methods, such as scintigraphy, single photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), and Raman spectroscopy. Therapeutic purposes of magnetic nanoconstructions are also promising. They are used for effective drug delivery, magnetic mediated hypertermia, and megnetodynamic triggering of apoptosis. Thus, magnetic nanotheranostics opens a new venue for complex differential diagnostics, and therapy of metastatic cancer.

Remote Actuation of Magnetic Nanoparticles For Cancer Cell Selective Treatment Through Cytoskeletal Disruption

Motion of micron and sub-micron size magnetic particles in alternating magnetic fields can activate mechanosensitive cellular functions or physically destruct cancer cells. However, such effects are usually observed with relatively large magnetic particles (>250 nm) that would be difficult if at all possible to deliver to remote sites in the body to treat disease. Here we show a completely new mechanism of selective toxicity of superparamagnetic nanoparticles (SMNP) of 7 to 8 nm in diameter to cancer cells. These particles are coated by block copolymers, which facilitates their entry into the cells and clustering in the lysosomes, where they are then magneto-mechanically actuated by remotely applied alternating current (AC) magnetic fields of very low frequency (50 Hz). Such fields and treatments are safe for surrounding tissues but produce cytoskeletal disruption and subsequent death of cancer cells while leaving healthy cells intact.

The antitumor effect of magnetic nanodisks and DNA aptamer conjugates

Here we describe a method of forming large arrays (up to 10(9) pieces) of free magnetic Ni-nanodisks 50 nm thick coated on both sides with layers of 5 nm thick Au. The antitumor effect of the magnetic nickel gold-coated nanodisks and DNA aptamer conjugates was evaluated in vivo and in vitro. Under the influence of rotating magnetic field, the studied nanodisks can cause the death of Ehrlich ascites carcinoma cells.

Effects of magnetic nanoparticles of Fe3O4 combinated with gambogic acid on apoptosis of SMMC-7721 cells

Objective

This study aims to investigate the potential benefit of combination therapy with magnetic nanoparticles of Fe₃O₄ (Fe₃O₄-MNP) and gambogic acid (GA) on SMMC-7721 cells.

Methods

The inhibition of proliferation of SMMC-7721 cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was calculated and analyzed by flow cytometry, and the expressions of the apoptosis-related protein were detected by Western blot.

Results

GA enhanced the cytotoxicity of SMMC-7721 cells in a dose-dependent manner. The Fe₃O₄-MNP itself had no obviously inhibitory effect, but it could enhance the effect of GA on proliferation of SMMC-7721 cells. The apoptotic rate of SMMC-7721 cells induced by combination of GA with Fe₃O₄-MNP was higher than that by GA alone. The expression levels of caspase-3 and caspase-8 after co-treatment of GA and Fe₃O₄-MNP were higher than that exposed to either GA or Fe₃O₄-MNP alone, while the levels of bcl-2 were downregulated.

Conclusion

Fe₃O₄-MNP can promote GA-induced apoptosis of SMMC-7721 cells, which may be related to the downregulation of Bcl-2 and upregulation of caspase-3.

Folate-conjugated nanoparticles as a potent therapeutic approach in targeted cancer therapy

The selective and efficient drug delivery to tumor cells can remarkably improve different cancer therapeutic approaches. There are several nanoparticles (NPs) which can act as a potent drug carrier for cancer therapy. However, the specific drug delivery to cancer cells is an important issue which should be considered before designing new NPs for in vivo application. It has been shown that cancer cells over-express folate receptor (FR) in order to improve their growth. As normal cells express a significantly lower levels of FR compared to tumor cells, it seems that folate molecules can be used as potent targeting moieties in different nanocarrier-based therapeutic approaches. Moreover, there is evidence which implies folate-conjugated NPs can selectively deliver anti-tumor drugs into cancer cells both in vitro and in vivo. In this review, we will discuss about the efficiency of different folate-conjugated NPs in cancer therapy.