Thermo-chemotherapeutic effects of magnetic nanoparticles on cancer cells

Abstract

Magnetic nanoparticle-based hyperthermia has garnered significant attention as a promising approach in cancer treatment. This study presents the synthesis and comprehensive evaluation of polyethylene glycol (PEG)-coated Fe₃O₄ nanoparticles, designed specifically for magnetic hyperthermia applications. The Fe₃O₄ nanoparticles were synthesized using the chemical coprecipitation method, followed by surface modification with PEG coating to enhance their biocompatibility and stability in biological systems. To characterize the synthesized nanoparticles, various advanced techniques were employed. X-ray powder diffraction (XRD) confirmed the crystalline structure of the Fe₃O₄ nanoparticles, revealing an inverse-spinel configuration with a crystallite size of 9.1 nm. Fourier-transform infrared spectroscopy (FTIR) further confirmed the successful coating of the nanoparticles with PEG, as evidenced by characteristic absorption bands. The magnetic properties were analysed by vibrating sample magnetometer (VSM), which indicated that both the uncoated Fe₃O₄ nanoparticles and the PEG-coated variants exhibited superparamagnetic behaviour, a key attribute for magnetic hyperthermia. The physical size of the uncoated Fe₃O₄ nanoparticles was determined using high-resolution transmission electron microscopy which showed an average size of 9.5 ± 0.12 nm. Upon PEG coating, dynamic light scattering (DLS) measurements revealed that the hydrodynamic size of the PEG-coated nanoparticles increased to 118 ± 0.25 nm from 87 ± 0.31 nm (bare Fe₃O₄), reflecting the successful addition of the PEG layer and its impact on particle size in solution. The magnetic hyperthermia efficiency of PEG-coated Fe₃O₄ nanoparticles was systematically evaluated by varying several key parameters: magnetic field frequency (ranging from 162 to 935.6 kHz), field strength (from 5 to 12 mT), and nanoparticle concentration (between 1 to 100 mg/mL). To assess their performance, the temperature rise in an aqueous dispersion of the nanoparticles as monitored over a 20 minutes time period. This temperature increase reflects the nanoparticle’s ability to generate heat when subjected to an alternating magnetic field, a critical factor for effective hyperthermia treatment in cancer therapy. The specific loss power (SLP), a measure of the nanoparticle’s heat-generating capacity, was calculated by using the corrected slope method. The analysis revealed a clear relationship between the SLP values and the tested parameters. Specifically, the SLP of the PEG-coated Fe₃O₄ nanoparticles increased linearly with both the frequency and strength of the magnetic field, meaning that higher frequencies and stronger fields led to greater heat generation. Conversely, the SLP values vii decreased exponentially as the concentration of nanoparticles increased, indicating that more diluted nanoparticle dispersions were more efficient at converting electromagnetic energy into heat. The conditions for magnetic hyperthermia efficiency were identified at a magnetic field frequency of 580.8 kHz, a field strength of 10 mT, and a nanoparticle concentration of 25 mg/mL. These findings demonstrate that the synthesized PEG-coated Fe₃O₄ nanoparticles exhibit strong potential as candidates for magnetic hyperthermia-based cancer treatment. Their ability to efficiently convert electromagnetic energy into heat under optimal conditions makes them promising for use in targeted, localized hyperthermia therapy, where precise heat delivery is essential for effective tumour cell destruction without harming surrounding healthy tissue. Magnetic nanoparticle-based hyperthermia, combined with chemotherapy, represents a promising and innovative strategy for cancer treatment. In this study, a targeted drug delivery system was developed, consisting of a doxorubicin (DOX)-loaded magnetic core, coated with polyethylene glycol (PEG), and functionalized with the targeting ligand [D-Trp6] luteinizing hormone-releasing hormone (LHRH) or Triptorelin. This system was designed to enhance the effectiveness of cancer therapy by selectively delivering DOX to cancer cells while simultaneously employing magnetic hyperthermia to further induce cell death. Fourier transform infrared (FTIR) spectroscopy confirmed the successful conjugation of the LHRH ligand to the PEG-coated magnetite (Fe₃O₄) nanoparticles, as evidenced by characteristic peaks in the spectrum. The drug loading efficiency of the LHRH-targeted PEG-coated Fe₃O₄ nanoparticles was analysed using UV–vis spectroscopy, revealing a 66 % loading efficiency for DOX, indicating that a substantial amount of the drug was successfully incorporated into the nanoparticles. To assess the therapeutic potential of these synthesized nanoparticles, their effects were tested on human lung cancer cells (A549) and human breast cancer cells (MCF-7) using an MTT cell viability assay. The LHRH-targeted PEG-coated Fe₃O₄ nanoparticles, loaded with DOX, were evaluated for cytotoxicity under three different treatment conditions: thermotherapy (magnetic hyperthermia), chemotherapy (DOX alone), and a combination of thermotherapy and chemotherapy (thermo-chemotherapy). In the A549 lung cancer cells, thermo-chemotherapy where both DOX and magnetic hyperthermia were applied resulted in an 88 % reduction in cell viability at the highest DOX concentration tested (10 µg/mL). This was a notable improvement over chemotherapy alone, which reduced cell viability of 62 %, and thermotherapy alone, viii which caused a 47 % reduction. A similar trend was observed in MCF-7 breast cancer cells, where thermo-chemotherapy led to a 91 % reduction in cell viability at highest DOX concentration (8 µg/mL), surpassing chemotherapy (57%) and thermotherapy (45 %) when used as standalone treatments. In addition to assessing cell viability, the study also explored the immune response generated by the treatment, specifically focusing on the production of interferon-gamma (IFN-γ), a cytokine known for its role in immune-mediated cancer cell inhibition. IFN-γ production was measured in A549 lung cancer cells using both targeted and non-targeted drug-loaded nanoparticle conjugates, with and without the application of an alternating magnetic field. The findings demonstrated that the use of targeted, DOX-loaded magnetic nanoparticles led to a significant increase in IFN-γ production, regardless of magnetic field application, compared to non-targeted nanoparticles. This suggests that the targeted delivery of DOX, coupled with the magnetic hyperthermia, not only enhances direct cell killing but may also stimulate a more robust immune response against the cancer cells. Overall, this study highlights the potential of targeted magnetic hyperthermia approach in combination with chemotherapy to significantly enhance the effectiveness of cancer treatment. The dual action of the therapy inducing direct cancer cell death through hyperthermia while delivering cytotoxic drugs like DOX along with the stimulation of an immune response through increased IFN-γ production, provides a compelling case for the use of this strategy in treating cancers such as lung and breast cancer. By leveraging the advantages of magnetic fields to focus treatment on tumour cells and increase drug efficacy, this combined thermo chemotherapy approach could offer a promising and more effective method for combating cancer.