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

Differential intracellular influence of cancer cells and normal cells on magnetothermal properties and magnetic hyperthermal effects of magnetic nanoparticles

Magnetic hyperthermia using heat locally generated by magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF) to ablate cancer cells has attracted enormous attention. The high accumulation of MNPs and slow heat dissipation generated in tumors are considered the dominant factors involved in magnetic hyperthermia. However, the influence of intracellular microenvironment on magnetic hyperthermia has been ignored. This study unveiled for the first time the critical role of intracellular microenvironment on magnetic hyperthermia. The intracellular microenvironments of cancer cells and normal cells showed different influence on the magnetothermal properties and magnetic hyperthermia effects of MNPs. The MNPs in cancer cells could generate higher temperatures and induce higher rates of apoptosis than those in normal cells. Compared with that of normal cells, the intracellular microenvironment of cancer cells was more conducive to Brownian relaxation and the dynamic magnetic response of internalized MNPs. The cancerous intracellular microenvironment had a discriminative effect on the magnetic hyperthermal effect of MNPs due to the low viscoelasticity of cancer cells, which was verified by the softening or stiffening of cells and simulation models created using viscous liquids or elastic hydrogels. These findings suggest that the intracellular microenvironment should be considered another critical factor of the magnetic hyperthermal effect of MNPs.

Effect of a Constant Magnetic Field on Cell Morphology and Migration Mediated by Cytoskeleton-Bound Magnetic Nanoparticles

Cell migration, shape maintenance, and intracellular signaling are closely linked to dynamic changes in cell morphology and the cytoskeleton. These processes involve the reorganization of the cytoskeleton within the cytoplasm, affecting all its key components: intermediate filaments, microtubules, and microfilaments. A promising strategy for remotely controlling cellular functions is the use of magnetic nanoparticles, which can influence cellular physiology. This approach, known as magnetogenetics, has been applied in various areas of cell and molecular biology. Applying a magnetic field allows for the non-invasive modulation of biochemical processes, cell migration, and morphological changes in cells containing magnetic nanoparticles. In our study, magnetic nanoparticles were conjugated with antibodies targeting cytoskeletal components, enabling the magnetically induced manipulation and deformation of the cell cytoskeleton. Our research introduces a novel approach to manipulating specific cytoskeletal components and altering cell polarity with spatial precision in vitro using magnetic nanoparticles associated with the cytoskeleton.

Antitumor activity of functionalized iron oxide nanoparticles in Ehrlich tumor carcinoma-bearing mice enhanced by magnetic field

Iron oxide nanoparticles show an intrinsic therapeutic effect on cancer growth. In vivo, the combination of iron oxide nanoparticles as magnetic particles and a low-frequency magnetic field significantly decreases the growth of Ehrlich tumor carcinoma in mice. Magnetic fields can vibrate and enhance iron oxide nanoparticles movement inside of cells, affecting their structure. In this study, iron oxide nanoparticles were synthesized and assessed by UV-visible spectrophotometer, dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The damage effects of iron oxide nanoparticles and low-frequency magnetic fields (0.5 T, 50 Hz) on tumor tissues were evaluated by assessment of DNA comet assay, and Fourier transformed infrared (FTIR), oxidative stress, assessment of inflammatory biomarkers, and histopathology studies. Also, the effect on the heart, liver, and kidney organs was studied. Our results suggest that iron oxide nanoparticles and magnetic fields could be applied to help in cancer treatment.

Preclinical Development of Magnetic Nanoparticles for Hyperthermia Treatment of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a very challenging disease with a very poor prognosis. It is characterized by a dense desmoplastic stroma that hampers drug penetration and limits the effectiveness of conventional chemotherapy (CT). As an alternative, the combination of CT with hyperthermia (HT) has been proposed as an innovative treatment modality for PDAC. In previous works, we reported on the development of iron oxide magnetic nanoparticles (MNPs) that, when exposed to time-varying magnetic fields, exhibit strong HT responses that inhibited the growth of pancreatic cancers. We report here on advances toward the clinical use of these MNPs as an intratumorally administered sterile magnetic fluid (the "NoCanTher ThermoTherapy" or "NTT" Agent) alongside intravenous standard-of-care drugs (gemcitabine and nab-paclitaxel) for the treatment of PDAC. In vitro cell viability assays show that the combination of low doses of CT and HT is highly synergistic, particularly in the BxPC-3 cell line. In vivo, biodistribution assays showed that the NTT Agent MNPs remained mainly within the tumor, concentrated around areas with a high stromal component. Moreover, the combined CT/HT treatment shows clear advantages over CT alone in terms of drug penetration and reduction of the tumor volume, suggesting a potential direct effect of HT in the disruption of the interstitial stroma to facilitate the access of the drugs to malignant cells. These studies have led to the approval and commencement of a clinical investigational study at the Vall d'Hebron University Hospital (Barcelona, Spain) of the NTT Agent alongside CT in patients with locally advanced PDAC.

Combination Using Magnetic Iron Oxide Nanoparticles and Magnetic Field for Cancer Therapy

Iron oxide nanoparticles (MNPs) demonstrate notable benefits in magnetic induction, attributed to their distinctive physical and chemical attributes. Emerging cancer treatment utilizing magnetic fields have also gathered increasing attention in the biomedical field. However, the defects of difficult dispersion and poor biocompatibility of MNPs seriously hinder their application. In order to overcome its inherent defects and maximize the therapeutic potential of MNPs, various functionalized MNPs have been developed, and numerous combined treatment methods based on MNPs have been widely studied. In this review, we compare and analyze the common nanoparticles based on MNPs with different sizes, shapes, and functional modifications. Additionally, we introduced the therapeutic mechanisms of the strategies, such as magnetically controlled targeting, magnetic hyperthermia, and magneto-mechanical effect, which based on the unique magnetic induction capabilities of MNPs. Finally, main challenges of MNPs as smart nanomaterials were also discussed. This review seeks to offer a thorough overview of MNPs in biomedicine and a new sight for their application in tumor treatment.

Comprehensive Analysis of the Potential Toxicity of Magnetic Iron Oxide Nanoparticles for Medical Applications: Cellular Mechanisms and Systemic Effects

Owing to recent advancements in nanotechnology, magnetic iron oxide nanoparticles (MNPs), particularly magnetite (Fe3O4) and maghemite (γ-Fe2O3), are currently widely employed in the field of medicine. These MNPs, characterized by their large specific surface area, potential for diverse functionalization, and magnetic properties, have found application in various medical domains, including tumor imaging (MRI), radiolabelling, internal radiotherapy, hyperthermia, gene therapy, drug delivery, and theranostics. However, ensuring the non-toxicity of MNPs when employed in medical practices is paramount. Thus, ongoing research endeavors are essential to comprehensively understand and address potential toxicological implications associated with their usage. This review aims to present the latest research and findings on assessing the potential toxicity of magnetic nanoparticles. It meticulously delineates the primary mechanisms of MNP toxicity at the cellular level, encompassing oxidative stress, genotoxic effects, disruption of the cytoskeleton, cell membrane perturbation, alterations in the cell cycle, dysregulation of gene expression, inflammatory response, disturbance in ion homeostasis, and interference with cell migration and mobility. Furthermore, the review expounds upon the potential impact of MNPs on various organs and systems, including the brain and nervous system, heart and circulatory system, liver, spleen, lymph nodes, skin, urinary, and reproductive systems.

Polyhedral magnetic nanoparticles induce apoptosis in gastric cancer stem cells and suppressing tumor growth through magnetic force generation

Gastric cancer is a prevalent malignant tumor worldwide, posing challenges due to its poor prognosis and limited treatment options. Cancer stem cells (CSCs) were demonstrated as a subset of cancer cells responsible for tumor initiation and progression, and their inherent resistance to conventional chemotherapy and radiotherapy critically contributes to tumor recurrence and metastasis. Promoting the eradication of cancer stem cells is crucial for enhancing the efficacy of cancer treatments. This study introduces a novel therapeutic strategy utilizing polyhedral magnetic nanoparticles (PMNPs) functionalized with CD44 antibodies and cell-penetrating peptides (CPPs) to improve uptake by gastric cancer stem cells (MCSCs). PMNPs, synthesized via thermal decomposition, exhibited a diameter of 90 nm ± 9 nm and a saturation magnetization of 79.9 emu/g. Functionalization enhanced their uptake capabilities. Under a rotating magnetic field (RMF) of 15 Hz, PMNPs disrupted cellular structure, leading to apoptosis and ferroptosis in MCSCs. The in vitro studies showed significant reduction in MCSCs viability, while in vivo studies demonstrated tumor growth suppression with minimal side effects and high biocompatibility. This work presents a novel strategy for designing magnetic nanoparticles to mechanically destroy cancer stem cells, offering a more efficient and safety treatment option for gastric cancer.

Cytoskeleton-modulating nanomaterials and their therapeutic potentials

The cytoskeleton, an intricate network of protein fibers within cells, plays a pivotal role in maintaining cell shape, enabling movement, and facilitating intracellular transport. Its involvement in various pathological states, ranging from cancer proliferation and metastasis to the progression of neurodegenerative disorders, underscores its potential as a target for therapeutic intervention. The exploration of nanotechnology in this realm, particularly the use of nanomaterials for cytoskeletal modulation, represents a cutting-edge approach with the promise of novel treatments. Inorganic nanomaterials, including those derived from gold, metal oxides, carbon, and black phosphorus, alongside organic variants such as peptides and proteins, are at the forefront of this research. These materials offer diverse mechanisms of action, either by directly interacting with cytoskeletal components or by influencing cellular signaling pathways that, in turn, modulate the cytoskeleton. Recent advancements have introduced magnetic field-responsive and light-responsive nanomaterials, which allow for targeted and controlled manipulation of the cytoskeleton. Such precision is crucial in minimizing off-target effects and enhancing therapeutic efficacy. This review explores the importance of research into cytoskeleton-targeting nanomaterials for developing therapeutic interventions for a range of diseases. It also addresses the progress made in this field, the challenges encountered, and future directions for using nanomaterials to modulate the cytoskeleton. The continued exploration of nanomaterials for cytoskeleton modulation holds great promise for advancing therapeutic strategies against a broad spectrum of diseases, marking a significant step forward in the intersection of nanotechnology and medicine.

Magnetic modulation of lysosomes for cancer therapy

Lysosomes play a central role in biochemical signal transduction and oxidative stress in cells. Inducing lysosome membrane penetration (LMP) to cause lysosomal-dependent cell death (LCD) in tumor cells is an effective strategy for cancer therapy. Chemical drugs can destroy the stability of lysosomes by neutralizing protons within the lysosomes or enhancing the fragility of the lysosomal membranes. However, there remain several unsolved problems of traditional drugs in LMP induction due to insufficient lysosomal targeting, fast metabolism, and toxicity in normal cells. With the development of nanotechnology, magnetic nanoparticles have been demonstrated to target lysosomes naturally, providing a versatile tool for lysosomal modulation. Combined with excellent tissue penetration and spatiotemporal manipulability of magnetic fields, magnetic modulation of lysosomes progresses rapidly in inducing LMP and LCD for cancer therapy. This review comprehensively discussed the strategies of magnetic modulation of lysosomes for cancer therapy. The intrinsic mechanisms of LMP-induced LCD were first introduced. Then, the modulation of lysosomes by diverse physical outputs of magnetic fields was emphatically discussed. Looking forward, this review will shed the light on the prospect of magnetic modulation of lysosomes, inspiring future research of magnetic modulation strategy in cancer therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

The efficient magneto-mechanical actuation of cancer cells using a very low concentration of non-interacting ferrimagnetic hexaferrite nanoplatelets

Magneto-mechanical actuation (MMA) using the low-frequency alternating magnetic fields (AMFs) of magnetic nanoparticles internalized into cancer cells can be used to irreparably damage these cells. However, nanoparticles in cells usually agglomerate, thus greatly augmenting the delivered force compared to single nanoparticles. Here, we demonstrate that MMA also decreases the cell viability, with the MMA mediated by individual, non-interacting nanoparticles. The effect was demonstrated with ferrimagnetic (i.e., permanently magnetic) barium-hexaferrite nanoplatelets (NPLs, ∼50 nm wide and 3 nm thick) with a unique, perpendicular orientation of the magnetization. Two cancer-cell lines (MDA-MB-231 and HeLa) are exposed to the NPLs in-vitro under different cell-culture conditions and actuated with a uniaxial AMF. TEM analyses show that only a small number of NPLs internalize in the cells, always situated in membrane-enclosed compartments of the endosomal-lysosomal system. Most compartments contain 1-2 NPLs and only seldom are the NPLs found in small groups, but never in close contact or mutually oriented. Even at low concentrations, the single NPLs reduce the cell viability when actuated with AMFs, which is further increased when the cells are in starvation conditions. These results pave the way for more efficient in-vivo MMA at very low particle concentrations.

Magneto-Mechanical Actuation Induces Endothelial Permeability

Cancer treatment is one of the major health problems that burden our society. According to the American Cancer Society, over 1.9 million new cancer cases and ∼0.6 million deaths from cancer are expected in the US in 2023. Therapeutic targeting is considered to be the gold standard in cancer treatment. However, when a tumor grows beyond a critical size, its vascular system differentiates abnormally and erratically, creating a heterogeneous endothelial barrier that further restricts drug delivery into tumors. While several methods exist, these prompt tumor migration and the appearance of new metastatic sites. Herein, we propose an innovative method based on magneto-mechanical actuation (MMA) to induce endothelial permeability. This method employs FDA-approved PEGylated superparamagnetic iron oxide nanoparticles (PEG-SPIONs) and alternating nonheating magnetic fields. MMA lies in the translation of magnetic forces into mechanical agitation. As a proof of concept, we developed a 2D cell culture model based on human umbilical vein endothelial cells (HUVEC), which were incubated with PEG-SPIONs and then exposed to different magnetic doses. After adjusting the particle concentration, incubation times, and parameters (amplitude, frequency, and exposure time) of the magnetic field generator, we induced actin filament remodeling and subsequent vascular endothelial-cadherin junction disruption. This led to transient gaps in cell monolayers, through which fluorescein isothiocyanate-dextran was translocated. We observed no cell viability reduction for 3 h of particle incubation up to a concentration of 100 μg/mL in the presence and absence of magnetic fields. For optimal permeability studies, the magnetic field parameters were adjusted to 100 mT, 65 Hz, and 30 min in a pulse mode with 5 min OFF intervals. We found that the endothelial permeability reached the highest value (33%) when 2 h postmagnetic field treatment was used. To explain these findings, a magneto-mechanical transduced stress mechanism mediated by intracellular forces was proposed. This method can open new avenues for targeted drug delivery into anatomic regions within the body for a broad range of disease interventions.

Disturbing cytoskeleton by engineered nanomaterials for enhanced cancer therapeutics

Cytoskeleton plays a significant role in the shape change, migration, movement, adhesion, cytokinesis, and phagocytosis of tumor cells. In clinical practice, some anti-cancer drugs achieve cytoskeletal therapeutic effects by acting on different cytoskeletal protein components. However, in the absence of cell-specific targeting, unnecessary cytoskeletal recombination in organisms would be disastrous, which would also bring about severe side effects during anticancer process. Nanomedicine have been proven to be superior to some small molecule drugs in cancer treatment due to better stability and targeting, and lower side effects. Therefore, this review summarized the recent developments of various nanomaterials disturbing cytoskeleton for enhanced cancer therapeutics, including carbon, noble metals, metal oxides, black phosphorus, calcium, silicon, polymers, peptides, and metal-organic frameworks, etc. A comprehensive analysis of the characteristics of cytoskeleton therapy as well as the future prospects and challenges towards clinical application were also discussed. We aim to drive on this emerging topic through refreshing perspectives based on our own work and what we have also learnt from others. This review will help researchers quickly understand relevant cytoskeletal therapeutic information to further advance the development of cancer nanomedicine.

Unveiling the Role of the Properties of Magnetic Nanoparticles for Highly Efficient Low-Frequency Magneto-Mechanical Actuation of Biomolecules

The role of the properties of magnetic nanoparticles in the remote magneto-mechanical actuation of biomolecules under the influence of external magnetic fields is still of particular interest. Here, a specially designed strategy based on the mechanical destruction of short oligonucleotide duplexes is used to demonstrate the effect of magnetic nanoparticles with different sizes (5-99 nm) on the magnitude of the magneto-mechanical actuations in a low-frequency alternating magnetic field. The results show that the mechanical destruction of complementary chains of duplexes, caused by the rotational-vibrational movements of nanoparticles upon exposure to a magnetic field, has a nonmonotonic dependence on the nanoparticle core size. The main hypothesis of this phenomenon is associated with a key role of magneto-dipole interactions between individual nanoparticles, which blocks the movements of nanoparticles in dense clusters. This result will allow fine-tuning of the magnetic nanoparticle properties for addressing specific magneto-mechanical tasks.

Magnetic Control of Protein Expression via Magneto-mechanical Actuation of ND-PEGylated Iron Oxide Nanocubes for Cell Therapy

Engineered cells used as smart vehicles for delivery of secreted therapeutic proteins enable effective treatment of cancer and certain degenerative, autoimmune, and genetic disorders. However, current cell-based therapies use mostly invasive tools for tracking proteins and do not allow for controlled secretion of therapeutic proteins, which could result in unconstrained killing of surrounding healthy tissues or ineffective killing of host cancer cells. Regulating the expression of therapeutic proteins after success of therapy remains elusive. In this study, a noninvasive therapeutic approach mediated by magneto-mechanical actuation (MMA) was developed to remotely regulate the expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein, which is secreted by transduced cells. Stem cells, macrophages, and breast cancer cells were transduced with a lentiviral vector encoding the SGpL2TR protein. SGpL2TR comprises TRAIL and GpLuc domains optimized for cell-based applications. Our approach relies on the remote actuation of cubic-shape highly magnetic field responsive superparamagnetic iron oxide nanoparticles (SPIONs) coated with nitrodopamine PEG (ND-PEG), which are internalized within the cells. Cubic ND-PEG-SPIONs actuated by superlow frequency alternating current magnetic fields can translate magnetic forces into mechanical motion and in turn spur mechanosensitive cellular responses. Cubic ND-PEG-SPIONs were artificially designed to effectively operate at low magnetic field strengths (<100 mT) retaining approximately 60% of their saturation magnetization. Compared to other cells, stems cells were more sensitive to the interaction with actuated cubic ND-PEG-SPIONs, which clustered near the endoplasmic reticulum (ER). Luciferase, ELISA, and RT-qPCR analyses revealed a marked TRAIL downregulation (secretion levels were depleted down to 30%) when intracellular particles at 0.100 mg/mL Fe were actuated by magnetic fields (65 mT and 50 Hz for 30 min). Western blot studies indicated actuated, intracellular cubic ND-PEG-SPIONs can cause mild ER stress at short periods (up to 3 h) of postmagnetic field treatment thus leading to the unfolded protein response. We observed that the interaction of TRAIL polypeptides with ND-PEG can also contribute to this response. To prove the applicability of our approach, we used glioblastoma cells, which were exposed to TRAIL secreted from stem cells. We demonstrated that in the absence of MMA treatment, TRAIL essentially killed glioblastoma cells indiscriminately, but when treated with MMA, we were able to control the cell killing rate by adjusting the magnetic doses. This approach can expand the capabilities of stem cells to serve as smart vehicles for delivery of therapeutic proteins in a controlled manner without using interfering and expensive drugs, while retaining their potential to regenerate damaged tissue after treatment. This approach brings forth new alternatives to regulate protein expression noninvasively for cell therapy and other cancer therapies.

Mechanical stimuli-driven cancer therapeutics

Mechanical stimulation utilizing deep tissue-penetrating and focusable energy sources, such as ultrasound and magnetic fields, is regarded as an emerging patient-friendly and effective therapeutic strategy to overcome the limitations of conventional cancer therapies based on fundamental external stimuli such as light, heat, electricity, radiation, or microwaves. Recent efforts have suggested that mechanical stimuli-driven cancer therapy (henceforth referred to as "mechanical cancer therapy") could provide a direct therapeutic effect and intelligent control to augment other anti-cancer systems as a synergistic combinational cancer treatment. This review article highlights the latest advances in mechanical cancer therapy to present a novel perspective on the fundamental principles of ultrasound- and magnetic field-mediated mechanical forces, including compression, tension, shear force, and torque, that can be generated in a cellular microenvironment using mechanical stimuli-activated functional materials. Additionally, this article will shed light on mechanical cancer therapy and inspire future research to pursue the development of ultrasound- and magnetic-field-activated materials and their applications in this field.

Combinatorial physical methods for cellular therapy: Towards the future of cellular analysis?

The physical energy activated techniques for cellular delivery and analysis is one of the most rapidly expanding research areas for a variety of biological and biomedical discoveries. These methods, such as electroporation, optoporation, sonoporation, mechanoporation, magnetoporation, etc., have been widely used in delivering different biomolecules into a range of primary and patient-derived cell types. However, the techniques when used individually have had limitations in delivery and co-delivery of diverse biomolecules in various cell types. In recent years, a number of studies have been performed by combining the different membrane disruption techniques, either sequentially or simultaneously, in a single study. The studies, referred to as combinatorial, or hybrid techniques, have demonstrated enhanced transfection, such as efficient macromolecular and gene delivery and co-delivery, at lower delivery parameters and with high cell viability. Such studies can open up new and exciting avenues for understanding the subcellular structure and consequently facilitate the development of novel therapeutic strategies. This review consequently aims at summarising the different developments in hybrid therapeutic techniques. The different methods discussed include mechano-electroporation, electro-sonoporation, magneto-mechanoporation, magnetic nanoparticles enhanced electroporation, and magnetic hyperthermia studies. We discuss the clinical status of the different methods and conclude with a discussion on the future prospects of the combinatorial techniques for cellular therapy and diagnostics.

Bifunctional Magnetite–Gold Nanoparticles for Magneto-Mechanical Actuation and Cancer Cell Destruction

Magnetite–gold dumbbell nanoparticles are essential for biomedical applications due to the presence of two surfaces with different chemical natures and the potential combination of magnetic and plasmonic properties. Here, the remote actuation of Fe3O4-Au hybrid particles in a rotating (1 Hz, 7 mT), static (7 mT) or pulsed low-frequency (31 Hz, 175 mT, 30 s pulse/30 s pause) magnetic field was studied. The particles were synthesized by a high-temperature wet chemistry protocol and exhibited superparamagnetic properties with the saturation magnetization of 67.9 ± 3.0 Am2 kg−1. We showcased the nanoparticles’ controlled aggregation in chains (rotating/static magnetic field) in an aqueous solution and their disaggregation when the field was removed. The investigation of nanoparticle uptake by LNCaP and PC-3 cancer cells demonstrated that Fe3O4-Au hybrids mainly escaped endosomes and accumulated in the cytoplasm. A significant fraction of them still responded to a rotating magnetic field, forming short chains. The particles were not toxic to cells at concentrations up to 210 μg (Fe3O4) mL−1. However, cell viability decrease after incubation with the nanoparticles (≥70 μg mL−1) and exposure to a pulsed low-frequency magnetic field was found. We ascribe this effect to mechanically induced cell destruction. Overall, this makes Fe3O4-Au nanostructures promising candidates for intracellular actuation for future magneto-mechanical cancer therapies.

Magneto-Mechanical Approach in Biomedicine: Benefits, Challenges, and Future Perspectives

The magneto-mechanical approach is a powerful technique used in many different applications in biomedicine, including remote control enzyme activity, cell receptors, cancer-selective treatments, mechanically-activated drug releases, etc. This approach is based on the use of a combination of magnetic nanoparticles and external magnetic fields that have led to the movement of such nanoparticles with torques and forces (enough to change the conformation of biomolecules or even break weak chemical bonds). However, despite many theoretical and experimental works on this topic, it is difficult to predict the magneto-mechanical effects in each particular case, while the important results are scattered and often cannot be translated to other experiments. The main reason is that the magneto-mechanical effect is extremely sensitive to changes in any parameter of magnetic nanoparticles and the environment and changes in the parameters of the applied magnetic field. Thus, in this review, we (1) summarize and propose a simplified theoretical explanation of the main factors affecting the efficiency of the magneto-mechanical approach; (2) discuss the nature of the MNP-mediated mechanical forces and their order of magnitude; (3) show some of the main applications of the magneto-mechanical approach in the control over the properties of biological systems.

Magneto-Endosomalytic Therapy for Cancer

A remarkably simple yet effective mode of cancer treatment is reported by repurposing clinically approved magnetic nanoparticles (MNPs). Intracellular nanoparticle self-assembly directed by static parallel magnetic fields leads to cell death in targeted tissues while leaving other cells and organs intact. This simple concept opens a new avenue to treat cancer, capitalizing on nanosciences and the nanoparticle (NP) design principles accumulated in the past decades.

Spatial Manipulation of Particles and Cells at Micro- and Nanoscale via Magnetic Forces

The importance of magnetic micro- and nanoparticles for applications in biomedical technology is widely recognised. Many of these applications, including tissue engineering, cell sorting, biosensors, drug delivery, and lab-on-chip devices, require remote manipulation of magnetic objects. High-gradient magnetic fields generated by micromagnets in the range of 103–105 T/m are sufficient for magnetic forces to overcome other forces caused by viscosity, gravity, and thermal fluctuations. In this paper, various magnetic systems capable of generating magnetic fields with required spatial gradients are analysed. Starting from simple systems of individual magnets and methods of field computation, more advanced magnetic microarrays obtained by lithography patterning of permanent magnets are introduced. More flexible field configurations can be formed with the use of soft magnetic materials magnetised by an external field, which allows control over both temporal and spatial field distributions. As an example, soft magnetic microwires are considered. A very attractive method of field generation is utilising tuneable domain configurations. In this review, we discuss the force requirements and constraints for different areas of application, emphasising the current challenges and how to overcome them.

Real-Time Observation and Analysis of Magnetomechanical Actuation of Magnetic Nanoparticles in Cells

The origin of cell death in the magnetomechanical actuation of cells induced by magnetic nanoparticle motion under low-frequency magnetic fields is still elusive. Here, a miniaturized electromagnet fitted under a confocal microscope is used to observe in real time cells specifically targeted by superparamagnetic nanoparticles and exposed to a low-frequency rotating magnetic field. Our analysis reveals that the lysosome membrane is permeabilized in only a few minutes after the start of magnetic field application, concomitant with lysosome movements toward the nucleus. Those events are associated with disorganization of the tubulin microtubule network and a change in cell morphology. This miniaturized electromagnet will allow a deeper insight into the physical, molecular, and biological process occurring during the magnetomechanical actuation of magnetic nanoparticles.

Cell Behavioral Changes after the Application of Magneto-Mechanical Activation to Normal and Cancer Cells

In vitro cell exposure to nanoparticles, depending on the applied concentration, can help in the development of theranostic tools to better detect and treat human diseases. Recent studies have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the behavior of cancer cells. In this work, the viability rate of MNP’s-manipulated cancerous (MCF-7, MDA-MB-231) and non-cancerous (MCF-10A) cells was investigated in three different types of low-frequency magnetic fields: static, pulsed, and rotating field mode. In the non-cancerous cell line, the cell viability decreased mostly in cells with internalized MNPs and those treated with the pulsed field mode. In both cancer cell lines, the pulsed field mode was again the optimum magnetic field, which together with internalized MNPs caused a large decrease in cells’ viability (50–55% and 70% in MCF-7 and MDA-MB-231, respectively) while the static and rotating field modes maintained the viability at high levels. Finally, F-actin staining was used to observe the changes in the cytoskeleton and DAPI staining was performed to reveal the apoptotic alterations in cells’ nuclei before and after magneto-mechanical activation. Subsequently, reduced cell viability led to a loss of actin stress fibers and apoptotic nuclear changes in cancer cells subjected to MNPs triggered by a pulsed magnetic field.

Magneto-mechanical destruction of cancer-associated fibroblasts using ultra-small iron oxide nanoparticles and low frequency rotating magnetic fields

The destruction of cells using the mechanical activation of magnetic nanoparticles with low-frequency magnetic fields constitutes a recent and interesting approach in cancer therapy. Here, we showed that superparamagnetic iron oxide nanoparticles as small as 6 nm were able to induce the death of pancreatic cancer-associated fibroblasts, chosen as a model. An exhaustive screening of the amplitude, frequency, and type (alternating vs. rotating) of magnetic field demonstrated that the best efficacy was obtained for a rotating low-amplitude low-frequency magnetic field (1 Hz and 40 mT), reaching a 34% ratio in cell death induction; interestingly, the cell death was not maximized for the largest amplitudes of the magnetic field. State-of-the-art kinetic Monte-Carlo simulations able to calculate the torque undergone by assemblies of magnetic nanoparticles explained these features and were in agreement with cell death experiments. Simulations showed that the force generated by the nanoparticles once internalized inside the lysosome was around 3 pN, which is in principle not large enough to induce direct membrane disruption. Other biological mechanisms were explored to explain cell death: the mechanical activation of magnetic nanoparticles induced lysosome membrane permeabilization and the release of the lysosome content and cell death was mediated through a lysosomal pathway depending on cathepsin-B activity. Finally, we showed that repeated rotating magnetic field exposure halted drastically the cell proliferation. This study established a proof-of-concept that ultra-small nanoparticles can disrupt the tumor microenvironment through mechanical forces generated by mechanical activation of magnetic nanoparticles upon low-frequency rotating magnetic field exposure, opening new opportunities for cancer therapy.

Poly(2-oxazoline)-magnetite NanoFerrogels: Magnetic field responsive theranostic platform for cancer drug delivery and imaging

Combining diagnosis and treatment approaches in one entity is the goal of theranostics for cancer therapy. Magnetic nanoparticles have been extensively used as contrast agents for nuclear magnetic resonance imaging as well as drug carriers and remote actuation agents. Poly(2-oxazoline)-based polymeric micelles, which have been shown to efficiently solubilize hydrophobic drugs and drug combinations, have high loading capacity (above 40% w/w) for paclitaxel. In this study, we report the development of novel theranostic system, NanoFerrogels, which is designed to capitalize on the magnetic nanoparticle properties as imaging agents and the poly(2-oxazoline)-based micelles as drug loading compartment. We developed six formulations with magnetic nanoparticle content of 0.3%-12% (w/w), with the z-average sizes of 85-130 nm and ξ-potential of 2.7-28.3 mV. The release profiles of paclitaxel from NanoFerrogels were notably dependent on the degree of dopamine grafting on poly(2-oxazoline)-based micelles. Paclitaxel loaded NanoFerrogels showed efficacy against three breast cancer lines which was comparable to free paclitaxel. They also showed improved tumor and lymph node accumulation and signal reduction in vivo (2.7% in tumor; 8.5% in lymph node) compared to clinically approved imaging agent ferumoxytol (FERAHEME®) 24 h after administration. NanoFerrogels responded to super-low frequency alternating current magnetic field (50 kA m-1, 50 Hz) which accelerated drug release from paclitaxel-loaded NanoFerrogels or caused death of cells loaded with NanoFerrogels. These proof-of-concept experiments demonstrate that NanoFerrogels have potential as remotely actuated theranostic platform for cancer diagnosis and treatment.

Magneto-mechanical treatment of human glioblastoma cells with engineered iron oxide powder microparticles for triggering apoptosis

In nanomedicine, treatments based on physical mechanisms are more and more investigated and are promising alternatives for challenging tumor therapy. One of these approaches, called magneto-mechanical treatment, consists in triggering cell death via the vibration of anisotropic magnetic particles, under a low frequency magnetic field. In this work, we introduce a new type of easily accessible magnetic microparticles (MMPs) and study the influence of their surface functionalization on their ability to induce such an effect, and its mechanism. We prepared anisotropic magnetite microparticles by liquid-phase ball milling of a magnetite powder. These particles are completely different from the often-used SPIONs: they are micron-size, ferromagnetic, with a closed-flux magnetic structure reminiscent of that of vortex particles. The magnetic particles were covered with a silica shell, and grafted with PEGylated ligands with various physicochemical properties. We investigated both bare and coated particles' in vitro cytotoxicity, and compared their efficiency to induce U87-MG human glioblastoma cell apoptosis under a low frequency rotating magnetic field (RMF). Our results indicated that (1) the magneto-mechanical treatment with bare MMPs induces a rapid decrease in cell viability whereas the effect is slower with PEGylated particles; (2) the number of apoptotic cells after magneto-mechanical treatment is higher with PEGylated particles; (3) a lower frequency of RMF (down to 2 Hz) favors the apoptosis. These results highlight a difference in the cell death mechanism according to the properties of particles used - the rapid cell death observed with the bare MMPs indicates a death pathway via necrosis, while PEGylated particles seem to favor apoptosis.

Magnetic Particle Imaging: An Emerging Modality with Prospects in Diagnosis, Targeting and Therapy of Cancer

BACKGROUND

Magnetic Particle Imaging (MPI) is an emerging imaging modality for quantitative direct imaging of superparamagnetic iron oxide nanoparticles (SPION or SPIO). With different physics from MRI, MPI benefits from ideal image contrast with zero background tissue signal. This enables clear visualization of cancer with image characteristics similar to PET or SPECT, but using radiation-free magnetic nanoparticles instead, with infinite-duration reporter persistence in vivo. MPI for cancer imaging: demonstrated months of quantitative imaging of the cancer-related immune response with in situ SPION-labelling of immune cells (e.g., neutrophils, CAR T-cells). Because MPI suffers absolutely no susceptibility artifacts in the lung, immuno-MPI could soon provide completely noninvasive early-stage diagnosis and treatment monitoring of lung cancers. MPI for magnetic steering: MPI gradients are ~150 × stronger than MRI, enabling remote magnetic steering of magneto-aerosol, nanoparticles, and catheter tips, enhancing therapeutic delivery by magnetic means. MPI for precision therapy: gradients enable focusing of magnetic hyperthermia and magnetic-actuated drug release with up to 2 mm precision. The extent of drug release from the magnetic nanocarrier can be quantitatively monitored by MPI of SPION's MPS spectral changes within the nanocarrier.

CONCLUSION

MPI is a promising new magnetic modality spanning cancer imaging to guided-therapy.

Advances in Magnetic Nanoparticles Engineering for Biomedical Applications-A Review

Magnetic iron oxide nanoparticles (MNPs) have been developed and applied for a broad range of biomedical applications, such as diagnostic imaging, magnetic fluid hyperthermia, targeted drug delivery, gene therapy and tissue repair. As one key element, reproducible synthesis routes of MNPs are capable of controlling and adjusting structure, size, shape and magnetic properties are mandatory. In this review, we discuss advanced methods for engineering and utilizing MNPs, such as continuous synthesis approaches using microtechnologies and the biosynthesis of magnetosomes, biotechnological synthesized iron oxide nanoparticles from bacteria. We compare the technologies and resulting MNPs with conventional synthetic routes. Prominent biomedical applications of the MNPs such as diagnostic imaging, magnetic fluid hyperthermia, targeted drug delivery and magnetic actuation in micro/nanorobots will be presented.

Assessing the Biocompatibility of Multi-Anchored Glycoconjugate Functionalized Iron Oxide Nanoparticles in a Normal Human Colon Cell Line CCD-18Co

We have previously demonstrated that iron oxide nanoparticles with dopamine-anchored heterobifunctional polyethylene oxide (PEO) polymer, namely PEO-IONPs, and bio-functionalized with sialic-acid specific glycoconjugate moiety (Neu5Ac(α2-3)Gal(β1-4)-Glcβ-sp), namely GM3-IONPs, can be effectively used as antibacterial agents against target Escherichia coli. In this study, we evaluated the biocompatibility of PEO-IONPs and GM3-IONPs in a normal human colon cell line CCD-18Co via measuring cell proliferation, membrane integrity, and intracellular adenosine triphosphate (ATP), glutathione GSH, dihydrorhodamine (DHR) 123, and caspase 3/7 levels. PEO-IONPs caused a significant decrease in cell viability at concentrations above 100 μg/mL whereas GM3-IONPs did not cause a significant decrease in cell viability even at the highest dose of 500 μg/mL. The ATP synthase activity of CCD-18Co was significantly diminished in the presence of PEO-IONPs but not GM3-IONPs. PEO-IONPs also compromised the membrane integrity of CCD-18Co. In contrast, cells exposed to GM3-IONPs showed significantly different cell morphology, but with no apparent membrane damage. The interaction of PEO-IONPs or GM3-IONPs with CCD-18Co resulted in a substantial decrease in the intracellular GSH levels in a time- and concentration-dependent manner. Conversely, levels of DHR-123 increased with IONP concentrations. Levels of caspase 3/7 proteins were found to be significantly elevated in cells exposed to PEO-IONPs. Based on the results, we assume GM3-IONPs to be biocompatible with CCD-18Co and could be further evaluated for selective killing of pathogens in vivo.

Understanding MNPs Behaviour in Response to AMF in Biological Milieus and the Effects at the Cellular Level: Implications for a Rational Design That Drives Magnetic Hyperthermia Therapy toward Clinical Implementation

Simple Summary

Magnetic hyperthermia therapy is an alternative treatment for cancer that complements traditional therapies and that has shown great promise in recent years. In this review, we assess the current applications of this therapy in order to understand why its translation from the laboratory to the clinic has been less smooth than was anticipated, identifying the possible bottlenecks and proposing solutions to the problems encountered.

Abstract

Hyperthermia has emerged as a promising alternative to conventional cancer therapies and in fact, traditional hyperthermia is now commonly used in combination with chemotherapy or surgery during cancer treatment. Nevertheless, non-specific application of hyperthermia generates various undesirable side-effects, such that nano-magnetic hyperthermia has arisen a possible solution to this problem. This technique to induce hyperthermia is based on the intrinsic capacity of magnetic nanoparticles to accumulate in a given target area and to respond to alternating magnetic fields (AMFs) by releasing heat, based on different principles of physics. Unfortunately, the clinical implementation of nano-magnetic hyperthermia has not been fluid and few clinical trials have been carried out. In this review, we want to demonstrate the need for more systematic and basic research in this area, as many of the sub-cellular and molecular mechanisms associated with this approach remain unclear. As such, we shall consider here the biological effects that occur and why this theoretically well-designed nano-system fails in physiological conditions. Moreover, we will offer some guidelines that may help establish successful strategies through the rational design of magnetic nanoparticles for magnetic hyperthermia.

Non-Heating Alternating Magnetic Field Nanomechanical Stimulation of Biomolecule Structures via Magnetic Nanoparticles as the Basis for Future Low-Toxic Biomedical Applications

The review discusses the theoretical, experimental and toxicological aspects of the prospective biomedical application of functionalized magnetic nanoparticles (MNPs) activated by a low frequency non-heating alternating magnetic field (AMF). In this approach, known as nano-magnetomechanical activation (NMMA), the MNPs are used as mediators that localize and apply force to such target biomolecular structures as enzyme molecules, transport vesicles, cell organelles, etc., without significant heating. It is shown that NMMA can become a biophysical platform for a family of therapy methods including the addressed delivery and controlled release of therapeutic agents from transport nanomodules, as well as selective molecular nanoscale localized drugless nanomechanical impacts. It is characterized by low system biochemical and electromagnetic toxicity. A technique of 3D scanning of the NMMA region with the size of several mm to several cm over object internals has been described.

Non-magnetic shell coating of magnetic nanoparticles as key factor of toxicity for cancer cells in a low frequency alternating magnetic field

This work is devoted to studying the effects of non-magnetic shell coating on nanoparticles in a low frequency alternating magnetic field (LF AMF) on tumor cells in vitro. Two types of iron oxide nanoparticles with the same magnetic core with and without silica shells were synthesized. Nanoparticles with silica shells significantly decreased the viability of PC3 cancer cells in a low frequency alternating magnetic field according to the cytotoxicity test, unlike uncoated nanoparticles. We showed that cell death results from the intracellular membrane integrity failure, and the calcium ions concentration increase with the subsequent necrosis. Transmission electron microscopy images showed that the uncoated silica nanoparticles are primarily found in an aggregated form in cells. We believe that uncoated nanoparticles lose their colloidal stability in an acidic endosomal environment after internalization into the cell due to surface etching and the formation of aggregates. As a result, they encounter high endosomal macromolecular viscosity and become unable to rotate efficiently. We assume that effective rotation of nanoparticles causes cell death. In turn, silica shell coating increases nanoparticles stability, preventing aggregation in endosomes. Thus, we propose that the colloidal stability of magnetic nanoparticles inside cells is one of the key factors for effective magneto-mechanical actuation.

Therapeutic strategies of iron-based nanomaterials for cancer therapy

Iron-based nanomaterials have appeared in various cancer treatments owing to their promising functions and safety. Various sophisticated iron-based nanomaterials have been designed to exhibit great therapeutic effects through different strategies. Given the rapid progression, there is a great need to integrate the recent advances to learn about the latest innovation in this field. In this review, we classified the strategies of iron-based nanomaterials for cancer treatment into the following categories: immunotherapy, ferroptosis, magnetic hyperthermia and magneto-mechanical destruction. On the one hand, we discussed the underlining mechanism of iron-based nanomaterials in these therapies and applications; on the other hand, we analyzed the feasible combination of these applications and other therapies. Finally, the current challenges and expectation of iron-based nanomaterials in this field were highlighted.

Magnetic Field-Mediated Control of Whole-Cell Biocatalysis

For decades, scientists have been looking for a way to control catalytic and biocatalytic processes through external physical stimuli. In this Letter, for the first time, we demonstrate the 150 ± 8% increase of the conversion of glucose to ethanol by Saccharomyces cerevisiae due to the application of a low-frequency magnetic field (100 Hz). This effect was achieved by the specially developed magnetic urchin-like particles, consisting of micrometer-sized core coated nanoneedles with high density, which could provide a biosafe permeabilization of cell membranes in a selected frequency and concentration range. We propose an acceleration mechanism based on magnetic field-induced cell membrane permeabilization. The ability to control cell metabolism without affecting their viability is a promising way for industrial biosynthesis to obtain a beneficial product with genetically engineered cells and subsequent improvement of biotechnological processes.

Cancer treatment by magneto-mechanical effect of particles, a review

Cancer treatment by magneto-mechanical effect of particles (TMMEP) is a growing field of research. The principle of this technique is to apply a mechanical force on cancer cells in order to destroy them thanks to magnetic particles vibrations. For this purpose, magnetic particles are injected in the tumor or exposed to cancer cells and a low-frequency alternating magnetic field is applied. This therapeutic approach is quite new and a wide range of treatment parameters are explored to date, as described in the literature. This review explains the principle of the technique, summarizes the parameters used by the different groups and reports the main in vitro and in vivo results.

Fe3O4@SiO2@Au nanoparticles for MRI-guided chemo/NIR photothermal therapy of cancer cells

Novel functionalized (biofunctionalization followed by cisplatin immobilization) Fe3O4@SiO2@Au nanoparticles (NPs) were designed. The encapsulation of Fe3O4 cores inside continuous SiO2 shells preserves their initial structure and strong magnetic properties, while the shell surface can be decorated by small Au NPs, and then cisplatin (cPt) can be successfully immobilized on their surface. The fabricated NPs exhibit very strong T 2 contrasting properties for magnetic resonance imaging (MRI). The functionalized Fe3O4@SiO2@Au NPs are tested for a potential application in photothermal cancer therapy, which is simulated by irradiation of two colon cancer cell lines (SW480 and SW620) with a laser (λ = 808 nm, W = 100 mW cm-2). It is found that the functionalized NPs possess low toxicity towards cancer cells (∼10-15%), which however could be drastically increased by laser irradiation, leading to a mortality of the cells of ∼43-50%. This increase of the cytotoxic properties of the Fe3O4@SiO2@Au NPs, due to the synergic effect between the presence of cPt plus Au NPs and laser irradiation, makes these NPs perspective agents for potential (MRI)-guided stimulated chemo-photothermal treatment of cancer.

Magneto-mechanical actuation of barium-hexaferrite nanoplatelets for the disruption of phospholipid membranes

HYPOTHESIS

The magneto-mechanical actuation (MMA) of magnetic nanoparticles with a low-frequency alternating magnetic field (AMF) can be used to destroy cancer cells. So far, MMA was tested on different cells using different nanoparticles and different field characteristics, which makes comparisons and any generalizations about the results of MMA difficult. In this paper we propose the use of giant unilamellar vesicles (GUVs) as a simple model system to study the effect of MMA on a closed lipid bilayer membrane, i.e., a basic building block of any cell.

EXPERIMENTS

The GUVs were exposed to barium-hexaferrite nanoplatelets (NPLs, ~50 nm wide and 3 nm thick) with unique magnetic properties dominated by a permanent magnetic moment that is perpendicular to the platelet, at different concentrations (1-50 µg/mL) and pH values (4.2-7.4) of the aqueous suspension. The GUVs were observed with an optical microscope while being exposed to a uniaxial AMF (3-100 Hz, 2.2-10.6 mT).

FINDINGS

When the NPLs were electrostatically attached to the GUV membranes, the MMA induced cyclic fluctuations of the GUVs' shape corresponding to the AMF frequency at the low NPL concentration (1 µm/mL), whereas the GUVs were bursting at the higher concentration (10 µg/mL). Theoretical considerations suggested that the bursting of the GUVs is a consequence of the local action of an assembly of several NPLs, rather than a collective effect of all the absorbed NPLs.

Magnetic Nanoparticles for Nanomedicine

The field of nanomedicine has recently emerged as a product of the expansion of a range of nanotechnologies into biomedical science, pharmacology and clinical practice. Due to the unique properties of nanoparticles and the related nanostructures, their applications to medical diagnostics, imaging, controlled drug and gene delivery, monitoring of therapeutic outcomes, and aiding in medical interventions, provide a new perspective for challenging problems in such demanding issues as those involved in the treatment of cancer or debilitating neurological diseases. In this review, we evaluate the role and contributions that the applications of magnetic nanoparticles (MNPs) have made to various aspects of nanomedicine, including the newest magnetic particle imaging (MPI) technology allowing for outstanding spatial and temporal resolution that enables targeted contrast enhancement and real-time assistance during medical interventions. We also evaluate the applications of MNPs to the development of targeted drug delivery systems with magnetic field guidance/focusing and controlled drug release that mitigate chemotherapeutic drugs’ side effects and damage to healthy cells. These systems enable tackling of multiple drug resistance which develops in cancer cells during chemotherapeutic treatment. Furthermore, the progress in development of ROS- and heat-generating magnetic nanocarriers and magneto-mechanical cancer cell destruction, induced by an external magnetic field, is also discussed. The crucial roles of MNPs in the development of biosensors and microfluidic paper array devices (µPADs) for the detection of cancer biomarkers and circulating tumor cells (CTCs) are also assessed. Future challenges concerning the role and contributions of MNPs to the progress in nanomedicine have been outlined.

Remote Actuation of Apoptosis in Liver Cancer Cells via Magneto-Mechanical Modulation of Iron Oxide Nanoparticles

Lysosome-activated apoptosis represents an alternative method of overcoming tumor resistance compared to traditional forms of treatment. Pulsed magnetic fields open a new avenue for controlled and targeted initiation of lysosomal permeabilization in cancer cells via mechanical actuation of magnetic nanomaterials. In this study we used a noninvasive tool; namely, a benchtop pulsed magnetic system, which enabled remote activation of apoptosis in liver cancer cells. The magnetic system we designed represents a platform that can be used in a wide range of biomedical applications. We show that liver cancer cells can be loaded with superparamagnetic iron oxide nanoparticles (SPIONs). SPIONs retained in lysosomal compartments can be effectively actuated with a high intensity (up to 8 T), short pulse width (~15 µs), pulsed magnetic field (PMF), resulting in lysosomal membrane permeabilization (LMP) in cancer cells. We revealed that SPION-loaded lysosomes undergo LMP by assessing an increase in the cytosolic activity of the lysosomal cathepsin B. The extent of cell death induced by LMP correlated with the accumulation of reactive oxygen species in cells. LMP was achieved for estimated forces of 700 pN and higher. Furthermore, we validated our approach on a three-dimensional cellular culture model to be able to mimic in vivo conditions. Overall, our results show that PMF treatment of SPION-loaded lysosomes can be utilized as a noninvasive tool to remotely induce apoptosis.

Magnetic liposome design for drug release systems responsive to super-low frequency alternating current magnetic field (AC MF)

HYPOTHESIS

Magnetic liposomes are shown to release the entrapped dye once modulated by low frequency AC MF. The mechanism and effectiveness of MF application should depend on lipid composition, magnetic nanoparticles (MNPs) properties, temperature and field parameters.

EXPERIMENTS

The study was performed using liposomes of various lipid composition and embedded hydrophobic MNPs. The liposomes structural changes were studied by the transmission electron microscopy (TEM) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and the leakage was monitored by the fluorescent dye release.

FINDINGS

Magnetic liposomes exposure to the AC MF resulted in the clustering of the MNPs in the membranes and disruption of the lipid packaging. Addition of cholesterol diminished the dye release from the saturated lipid-based liposomes. Replacement of the saturated lipid for unsaturated one also decreased the dye release. The dye release depended on the strength, but not the frequency of the field. Thus, the oscillating motion of MNPs in AC MF ruptures the gel phase membranes of saturated lipids. As the temperature increases the disruption also increases. In the liquid crystalline membranes formed by unsaturated lipids the deformations and defects created by mechanical motion of the MNPs are more likely to heal and results in decreased release.

Cell-Promoted Nanoparticle Aggregation Decreases Nanoparticle-Induced Hyperthermia under an Alternating Magnetic Field Independently of Nanoparticle Coating, Core Size, and Subcellular Localization

Magnetic hyperthermia has a significant potential to be a new breakthrough for cancer treatment. The simple concept of nanoparticle-induced heating by the application of an alternating magnetic field has attracted much attention, as it allows the local heating of cancer cells, which are considered more susceptible to hyperthermia than healthy cells, while avoiding the side effects of traditional hyperthermia. Despite the potential of this therapeutic approach, the idea that local heating effects due to the application of alternating magnetic fields on magnetic nanoparticle-loaded cancer cells can be used as a treatment is controversial. Several studies indicate that the heating capacity of magnetic nanoparticles is largely reduced in the cellular environment because of increased viscosity, aggregation, and dipolar interactions. However, an increasing number of studies, both in vitro and in vivo, show evidence of successful magnetic hyperthermia treatment on several different types of cancer cells. This apparent contradiction might be due to the use of different experimental conditions. Here, we analyze the effects of several parameters on the cytotoxic efficiency of magnetic nanoparticles as heat inductors under an alternating magnetic field. Our results indicate that the cell-nanoparticle interaction reduces the cytotoxic effects of magnetic hyperthermia, independent of nanoparticle coating and core size, the cell line used, and the subcellular localization of nanoparticles. However, there seems to occur a synergistic effect between the application of an external source of heat and the presence of magnetic nanoparticles, leading to higher toxicities than those induced by heat alone or the accumulation of nanoparticles within cells.

Size-selected Fe3O4-Au hybrid nanoparticles for improved magnetism-based theranostics

Size-selected Fe₃O₄-Au hybrid nanoparticles with diameters of 6-44 nm (Fe₃O₄) and 3-11 nm (Au) were prepared by high temperature, wet chemical synthesis. High-quality Fe₃O₄ nanocrystals with bulk-like magnetic behavior were obtained as confirmed by the presence of the Verwey transition. The 25 nm diameter Fe₃O₄-Au hybrid nanomaterial sample (in aqueous and agarose phantom systems) showed the best characteristics for application as contrast agents in magnetic resonance imaging and for local heating using magnetic particle hyperthermia. Due to the octahedral shape and the large saturation magnetization of the magnetite particles, we obtained an extraordinarily high r ₂-relaxivity of 495 mM^-1·s^-1 along with a specific loss power of 617 W·g_Fe ^-1 and 327 W·g_Fe ^-1 for hyperthermia in aqueous and agarose systems, respectively. The functional in vitro hyperthermia test for the 4T1 mouse breast cancer cell line demonstrated 80% and 100% cell death for immediate exposure and after precultivation of the cells for 6 h with 25 nm Fe₃O₄-Au hybrid nanomaterials, respectively. This confirms that the improved magnetic properties of the bifunctional particles present a next step in magnetic-particle-based theranostics.