How a High-Gradient Magnetic Field Could Affect Cell Life

The Review of Bioeffects of Static Magnetic Fields on the Oral Tissue-Derived Cells and Its Application in Regenerative Medicine

Magnets have been widely used in dentistry for orthodontic tooth movement and denture retention. Nevertheless, criticisms have arisen regarding the biosafety of static magnetic field (SMF) effects on surrounding tissues. Various controversial pieces of evidence have been discussed regarding SMFs on cellular biophysics, but little consensus has been reached, especially in the field of dentistry. Thus, the present paper will first review the safe use of SMFs in the oral cavity and as an additive therapy to orthodontic tooth movement and periodontium regeneration. Then, studies regarding SMF-incorporated implants are reviewed to investigate the advantageous effects of SMFs on osseointegration and the underlying mechanisms. Finally, a review of current developments in dentistry surrounding the combination of magnetic nanoparticles (MNPs) and SMFs is made to clarify potential future clinical applications.

Intravenous SPION-labeled adipocyte-derived stem cells targeted to the brain by magnetic attraction in a rat stroke model: An ultrastructural insight into cell fate within the brain

Mesenchymal stem cell therapy after stroke is a promising option investigated in animal models and clinical trials. The intravenous route is commonly used in clinical settings guaranteeing an adequate safety profile although low yields of engraftment. In this report, rats subjected to ischemic stroke were injected with adipose-derived stem cells (ADSCs) labeled with superparamagnetic iron oxide nanoparticles (SPIONs) applying an external magnetic field in the skull to retain the cells. Although most published studies demonstrate viability of ADSCs, only a few have used ultrastructural techniques. In our study, the application of a local magnetic force resulted in a tendency for higher yields of SPION-ADSCs targeting the brain. However, grafted cells displayed morphological signs of death, one day after administration, and correlative microscopy showed active microglia and astrocytes associated in the process of scavenging. Thus, we conclude that, although successfully targeted within the brain, SPION-ADSCs viability was rapidly compromised.

Response to Static Magnetic Field-Induced Stress in Scenedesmus obliquus and Nannochloropsis gaditana

Magnetic fields in biological systems is a promising research field; however, their application for microalgae has not been fully exploited. This work aims to measure the enzymatic activity and non-enzymatic activity of two microalgae species in terms of superoxide dismutase (SOD), catalase (CAT), and carotenoids, respectively, in response to static magnetic fields-induced stress. Two magnet configurations (north and south) and two exposure modes (continuous and pulse) were applied. Two microalgae species were considered, the Scenedesmus obliquus and Nannochloropsis gaditana. The SOD activity increased by up to 60% in S. obliquus under continuous exposure. This trend was also found for CAT in the continuous mode. Conversely, under the pulse mode, its response was hampered as the SOD and CAT were reduced. For N. gaditana, SOD increased by up to 62% with the south configuration under continuous exposure. In terms of CAT, there was a higher activity of up to 19%. Under the pulsed exposure, SOD activity was up to 115%. The CAT in this microalga was increased by up to 29%. For N. gaditana, a significant increase of over 40% in violaxanthin production was obtained compared to the control, when the microalgae were exposed to SMF as a pulse. Depending on the exposure mode and species, this methodology can be used to produce oxidative stress and obtain an inhibitory or enhanced response in addition to the significant increase in the production of antioxidant pigments.

Innovative technique for patterning Nd-Fe-B arrays and development of a microfluidic device with high trapping efficiency

Trapping/separating bio-entities via magnetic field gradients created a vast number of possibilities to develop biosensors for the early detection of diseases without the need for expensive equipment or physician/lab technicians. Thus, opening a window for at-home disposable rapid test kits. In the scope of the current work, an innovative and cost-effective technique to form well-organized arrays of Nd-Fe-B patterns was successfully developed. High aspect ratio Nd-Fe-B flakes were synthesized by surfactant-assisted ball milling technique. Nd-Fe-B flakes were distributed and patterned into a PDMS matrix by the aforementioned technique. A microfluidic channel was integrated on the fabricated Nd-Fe-B/PDMS patch with a high magnetic field gradient to form a microfluidic device. Fe nanoparticles, suspended in hexane, were flowed through the microfluidic channel, and trapping of the magnetic nanoparticles was observed. More experiments would be needed to quantitatively study efficiency. Ergo, the microfluidic device with high trapping efficiency was developed. The established technique has the potential to outperform the precedents in trapping efficiency, cost, and ease of production. The developed device could be integrated into disposable test kits for the early detection of various diseases.

Effect of High Static Magnetic Field (2 T-12 T) Exposure on the Mineral Element Content in Mice

Relative stability of mineral elements in tissues is necessary for health. High static magnetic fields (HiSMFs) have been widely used in biomedical research and industry. However, the bioeffect of HiSMFs on animals is still unclear. In this study, we investigated the effects of HiSMF exposure on the levels of Mg, Fe, Zn, Ca, and Cu in the main organs of mice. The 8-week male C57BL/6 mice were treated by 2-4 T, 6-8 T, 10-12 T HiSMFs for 28 days. The mass fractions of Mg, Fe, Zn, Ca, and Cu in the liver, brain, kidney, and heart in mice were respectively measured by atomic absorption spectroscopy, and used to evaluate mineral element content in tissues. The 2-4 T HiSMF exposure has increased the Mg, Fe, and Ca content in the kidney, as well as the Zn content in the brain. The 6-8 T HiSMF exposure has increased the Zn level in the liver; Mg, Fe, and Ca levels in the kidney; and Fe level in the heart, while the Zn in the kidney, and Zn and Ca in the heart was decreased by 6-8 T HiSMF exposure. For the 10-12 T HiSMF exposure, the Mg in the kidney, the Fe in the liver and kidney, and Cu in the brain have been increased significantly. However, the Zn in the kidney and the Ca in the brain and the heart were reduced by 10-12 T HiSMF exposure. The HiSMF exposure for 28 days can alter the Mg, Fe, Zn, Ca, and Cu content in mice, and change with the different magnetic flux density of HiSMFs (2-4 T, 6-8 T, 10-12 T), elements, and organ types.

Effect of magnetic field on the growth of the cultured Entamoeba histolytica isolated from patients in Palestine

Static magnetic field (SMF) is generated in vicinity of moving charge or current passing through conductor. In this study, we aimed to investigate the effect of SMF on the growth of the cultured Entamoeba histolytica (E. histolytica) trophozoites. Different SMF strengths with maximum value equals 30 mT (mT) was applied on the E.histolytica for different periods of times: 0 h, 24 h, 48 h, and 72 h. A modified diphasic liver infusion agar medium was used for culturing E. histolytica in vitro. The results showed the successful stabilization of culture of E. histolytica trophozoites. If we kept the sample for longer time, e. g. 14 days, the growth rate decreases to zero. When applying 10 mT and 15 mT SMF on the sample, it is found that the cultivated E. histolytica trophozoites dies after 4 and 2 days respectively. The experiments suggested that the SMF inhibited the growth and the propagation of E. histolytica cells. In addition, it completely killed all the cells in a short time interval which depend on the SMF strength. It is concluded that the SMFs inhibits the growth of E. histolytica and change the morphology of these cells. Thus, we recommend to use SMF as treatment to mitigate the growth of E. histolytica.

Neurobiophysics and Strategies in Neural Stimulation

Collapse

Design and operation of magnetophoretic systems at microscale: Device and particle approaches

Combining both device and particle designs are the essential concepts to be considered in magnetophoretic system development. Researcher efforts are often dedicated to only one of these design aspects and neglecting the interplay between them. Herein, to bring out importance of the idea of integration between device and particle, we reviewed the working principle of magnetophoretic system (includes both device and particle design concepts). Since, the magnetophoretic force is influenced by both field gradient and magnetization volume, hence, accurate prediction of the magnetophoretic force is relying on the availability of information on both parameters. In device design, we focus on the different strategies used to create localized high-field gradient. For particle design, we emphasize on the scaling between hydrodynamic size and magnetization volume. Moreover, we also briefly discussed the importance of magnetoshape anisotropy related to particle design aspect of magnetophoretic systems. Next, we illustrated the need for integration between device and particle design using microscale applications of magnetophoretic systems, include magnetic tweezers and microfluidic systems, as our working example. On the basis of our discussion, we highlighted several promising examples of microscale magnetophoretic systems which greatly utilized the interplay between device and particle design. Further, we concluded the review with several factors that possibly resulted in the lack of research efforts related to device and particle design integration.

Cell transmembrane potential in contactless permeabilization by time-varying magnetic fields

BACKGROUND

Although experimental results proved the feasibility of using time-varying magnetic field as a contactless cells permeabilization method, the underlying mechanism is still poorly understood. In this study a numerical analysis of the time-dependent transmembrane potential (TMP) at cell membranes during permeabilization by time-varying magnetic fields was proposed, and a first quantification of mechanical stress induced by the magnetic and electric fields, hypothesized to play an important role in the permeabilization mechanism, was carried out.

METHODS

Starting from the simulation of real in vitro experimental conditions, the analysis was widened quantifying the influence of pulse frequency, cell dimension and distance of the cell from the magnetic field source. The mechanical pressure on cell membrane due to the interaction between free charges and induced electric field and due to the gradient of the magnetic field was quantified in all those conditions in which the TMP values were not high enough to cause membrane permeabilization.

RESULTS

TMP values induced by typical in-vitro experimental conditions were far below the values needed for membrane permeabilization, with a strong dependence on pulse frequency and distance of the cell from the coil.

CONCLUSION

The preliminary assessment of the mechanical pressure on cell membrane showed that stress values evaluated in conditions in which TMP values were too low to cause membrane permeabilization were comparable to those known to influence the pores opening mechanisms. Results represent a significant step towards a better comprehension of the mechanism underlying cell membrane permeabilization by time-varying magnetic fields.

Dosimetry of pulsed magnetic field towards attaining bacteriostatic effect on Enterococcus faecalis: Implications for endodontic therapy

AIM

To examine in a laboratory setting the efficacy of moderate to high strength magnetic fields, as a potential bacteriostatic stimulus, against Enterococcus faecalis, one of the causative agents for infection during root canal treatments.

METHODOLOGY

Four different strengths (1, 2, 3 and 4 T) of the pulsed magnetic field (PMF) were applied in thirty repetitions to bacterial suspension. A pickup coil setup was used to measure the electromotive force induced inside the bacterial suspensions. The optical density (OD) was monitored over time (for 16 h 40 min) during the post-treatment period to assess bacterial growth. Along with the change in OD values, live/dead assay, membrane depolarization study, atomic force microscopy (AFM), scanning electron microscopy (SEM) and reactive oxygen species (ROS) assay on selected samples were studied to evaluate the effect of PMFs. All results were analysed using one-way ANOVA followed by post hoc Tukey test and considered significant at p < .05. Regression analysis (at a confidence of 95%, α = 0.05) was performed on the bacterial growth and membrane depolarization studies to determine progressive changes of the outcomes.

RESULTS

The peak value of the induced electromotive force was recorded as 0.25 V, for the 4 T magnetic field pulse with a pulse width of 16 ms. There was a significant arrest of bacterial cell growth after an exposure to PMFs of 1 T, 3 T and 4 T (ANOVA score: F (4, 495) =395.180 at p = .05). The image-based qualitative results of the live/dead assay using fluorescence microscopy techniques indicated that an exposure to higher PMFs (3 T/ 4 T) induced a bacteriostatic effect in a longer post-exposure timescale. Evidence of altered membrane potential within the 2 h of exposure to 4 T PMF was supported by the incidence of elevated ROS. For the ROS assay, a significant difference occurred for 4 T exposed samples (ANOVA score: calculated F (1, 3) =20.2749 at p = .05). SEM and AFM observations corroborated with the outcomes, by portraying significant membrane damage.

CONCLUSION

In a laboratory setting, PMFs with higher magnitudes (3 T and 4 T) were capable of inducing bacteriostatic effects on E. faecalis.

Nonviral Locally Injected Magnetic Vectors for In Vivo Gene Delivery: A Review of Studies on Magnetofection

Magnetic nanoparticles have been widely used in nanobiomedicine for diagnostics and the treatment of diseases, and as carriers for various drugs. The unique magnetic properties of "magnetic" drugs allow their delivery in a targeted tumor or tissue upon application of a magnetic field. The approach of combining magnetic drug targeting and gene delivery is called magnetofection, and it is very promising. This method is simple and efficient for the delivery of genetic material to cells using magnetic nanoparticles controlled by an external magnetic field. However, magnetofection in vivo has been studied insufficiently both for local and systemic routes of magnetic vector injection, and the relevant data available in the literature are often merely descriptive and contradictory. In this review, we collected and systematized the data on the efficiency of the local injections of magnetic nanoparticles that carry genetic information upon application of external magnetic fields. We also investigated the efficiency of magnetofection in vivo, depending on the structure and coverage of magnetic vectors. The perspectives of the development of the method were also considered.

Tracking of Zinc Ferrite Nanoparticle Effects on Pea (Pisum sativum L.) Plant Growth, Pigments, Mineral Content and Arbuscular Mycorrhizal Colonization

Important gaps in knowledge remain regarding the potential of nanoparticles (NPs) for plants, particularly the existence of helpful microorganisms, for instance, arbuscular mycorrhizal (AM) fungi present in the soil. Hence, more profound studies are required to distinguish the impact of NPs on plant growth inoculated with AM fungi and their role in NP uptake to develop smart nanotechnology implementations in crop improvement. Zinc ferrite (ZnFe₂O₄) NPs are prepared via the citrate technique and defined by X-ray diffraction (XRD) as well as transmission electron microscopy for several physical properties. The analysis of the XRD pattern confirmed the creation of a nanocrystalline structure with a crystallite size equal to 25.4 nm. The effects of ZnFe₂O₄ NP on AM fungi, growth and pigment content as well as nutrient uptake of pea (Pisum sativum) plants were assessed. ZnFe₂O₄ NP application caused a slight decrease in root colonization. However, its application showed an augmentation of 74.36% and 91.89% in AM pea plant shoots and roots’ fresh weights, respectively, compared to the control. Moreover, the synthesized ZnFe₂O₄ NP uptake by plant roots and their contents were enhanced by AM fungi. These findings suggest the safe use of ZnFe₂O₄ NPs in nano-agricultural applications for plant development with AM fungi.

Effects of modulation on sodium and potassium channel currents by extremely low frequency electromagnetic fields stimulation on hippocampal CA1 pyramidal cells

To investigate the effects of extremely low-frequency electromagnetic fields (ELF-EMFs) stimulation on sodium channel currents (I_Na), transient outward potassium channel currents (I_A) and delayed rectifier potassium channel currents (I_K) on hippocampal CA1 pyramidal neurons of young Sprague-Dawley rats. CA1 pyramidal neurons of rat hippocampal slices were subjected to ELF-EMFs stimulation with different frequencies (15 and 50 Hz), intensities (0.5, 1 and 2 mT) and durations (10, 20 and 30 min). The I_Na, I_A and I_K of neurons were recorded by a whole-cell patch-clamp method. ELF-EMFs stimulation enhanced I_Na densities, and depressed I_A and I_K densities. In detail, I_Na was more sensitive to the variation of intensities and frequencies of ELF-EMFs, whereas I_A and I_K were mainly affected by the variation of the duration of ELF-EMFs. ELF-EMFs stimulation altered activation and deactivation properties of I_Na, I_A and I_K. ELF-EMFs stimulation plays a role as a regulator rather than an inducer for ion channels. It might change the transition probability of ion channel opening or closing, and might also change the structure and function of the ion channel which need to be proved by the further technical method.

Magnetic Field Induced Changes in the Shoot and Root Proteome of Barley (Hordeum vulgare L.)

The geomagnetic field (GMF) has been present since the beginning of plant evolution. Recently, some researchers have focused their efforts on employing magnetic fields (MFs) higher than GMF to improve the seed germination, growth, and harvest of agriculturally important crop plants, as the use of MFs is an inexpensive and environment-friendly technique. In this study, we have employed different treatments of MF at 7 mT (milliTesla) at different time points of exposure, including 1, 3, and 6 h. The extended exposure was followed by five consecutive days at 6 h per day in barley seeds. The results showed a positive impact of MF on growth characteristics for 5-day-old seedlings, including seed germination rate, root and shoot length, and biomass weight. Furthermore, ~5 days of delay of flowering in pre-treated plants was also observed. We used a shotgun proteomics approach to identify changes in the protein signatures of root and shoot tissues under MF effects. In total, we have identified 2,896 proteins. Thirty-eight proteins in the shoot and 15 proteins in the root showed significant changes under the MF effect. Proteins involved in primary metabolic pathways were increased in contrast to proteins with a metal ion binding function, proteins that contain iron ions in their structure, and proteins involved in electron transfer chain, which were all decreased significantly in the treated tissues. The upregulated proteins' overall biological processes included carbohydrate metabolic process, oxidation-reduction process, and cell redox homeostasis, while down-regulated processes included translation and protein refolding. In general, shoot response was more affected by MF effect than root tissue, leading to the identification of 41 shoot specific proteins. This study provides an initial insight into the proteome regulation response to MF during barley's seedling stage.

Advantages and Limitations of Current Microgravity Platforms for Space Biology Research

Human Space exploration has created new challenges and new opportunities for science. Reaching beyond the Earth’s surface has raised the issue of the importance of gravity for the development and the physiology of biological systems, while giving scientists the tools to study the mechanisms of response and adaptation to the microgravity environment. As life has evolved under the constant influence of gravity, gravity affects biological systems at a very fundamental level. Owing to limited access to spaceflight platforms, scientists rely heavily on on-ground facilities that reproduce, to a different extent, microgravity or its effects. However, the technical constraints of counterbalancing the gravitational force on Earth add complexity to data interpretation. In-flight experiments are also not without their challenges, including additional stressors, such as cosmic radiation and lack of convection. It is thus extremely important in Space biology to design experiments in a way that maximizes the scientific return and takes into consideration all the variables of the chosen setup, both on-ground or on orbit. This review provides a critical analysis of current ground-based and spaceflight facilities. In particular, the focus was given to experimental design to offer the reader the tools to select the appropriate setup and to appropriately interpret the results.

Innate Immune Regulation Under Magnetic Fields With Possible Mechanisms and Therapeutic Applications

With the wide applications of magnetic fields (MFs) in medicine, researchers from different disciplines have gained interest in understanding the effect of various types of MFs on living cells and organisms. In this paper, we mainly focus on the immunological and physical aspects of the immune responses and their mechanisms under different types of MFs. Immune cells were slightly affected by low-frequency alternating MFs but were strongly influenced by moderate-intensity MFs and high-gradient MFs (HGMFs). Larger immune cells, such as macrophages, were more sensitive to HGMFs, which biased the cell polarization into the anti-inflammatory M2 phenotype. Subject to the gradient forces of varying directions and strength, the elongated M2 macrophage also remodeled the cytoskeleton with actin polymerization and changed the membrane receptors and ion channel gating. These alterations were very similar to changes caused by the small GTPase RhoA interference in macrophage. Regulation of iron metabolism may also contribute to the MF effects in macrophages. High MFs were found to regulate the iron content in monocyte-/macrophage-derived osteoclasts by affecting the expression of iron-regulation genes. On the other hand, paramagnetic nanoparticles (NPs) combined with external MFs play an important role in T-cell immunity. Paramagnetic NP-coated T-cells can cluster their T-cell receptors (TCRs) by using an external MF, thus increasing the cell–cell contact and communication followed by enhanced tumor killing capacity. The external MF can also guide the adoptively transferred magnetic NP-coated T-cells to their target sites in vivo, thus dramatically increasing the efficiency of cell therapy. Additionally, iron oxide NPs for ferroptosis-based cancer therapy and other MF-related therapeutic applications with obstacles were also addressed. Furthermore, for a profound understanding of the effect of MFs on immune cells, multidisciplinary research involving both experimental research and theoretical modeling is essential.

Designer nanocarriers for navigating the systemic delivery of oncolytic viruses

Nanotechnology is paving the way for new carrier systems designed to overcome the greatest challenges of oncolytic virotherapy; systemic administration and subsequent implications of immune responses and specific cell binding and entry. Systemic administration of oncolytic agents is vital for disseminated neoplasms, however transition of nanoparticles (NP) to virotherapy has yielded modest results. Their success relies on how they navigate the merry-go-round of often-contradictory phases of NP delivery: circulatory longevity, tissue permeation and cellular interaction, with many studies postulating design features optimal for each phase. This review discusses the optimal design of NPs for the transport of oncolytic viruses within these phases, to determine whether improved virotherapeutic efficacy lies in the pharmacokinetic/pharmacodynamics characteristics of the NP-oncolytic viruses complexes rather than manipulation of the virus and targeting ligands.

A Novel In Vitro Device to Deliver Induced Electromagnetic Fields to Cell and Tissue Cultures

We have developed a novel, to our knowledge, in vitro instrument that can deliver intermediate-frequency (100-400 kHz), moderate-intensity (up to and exceeding 6.5 V/cm pk-pk) electric fields (EFs) to cell and tissue cultures generated using induced electromagnetic fields (EMFs) in an air-core solenoid coil. A major application of these EFs is as an emerging cancer treatment modality. In vitro studies by Novocure reported that intermediate-frequency (100-300 kHz), low-amplitude (1-3 V/cm) EFs, which they called "tumor-treating fields (TTFields)," had an antimitotic effect on glioblastoma multiforme (GBM) cells. The effect was found to increase with increasing EF amplitude. Despite continued theoretical, preclinical, and clinical study, the mechanism of action remains incompletely understood. All previous in vitro studies of "TTFields" have used attached, capacitively coupled electrodes to deliver alternating EFs to cell and tissue cultures. This contacting delivery method suffers from a poorly characterized EF profile and conductive heating that limits the duration and amplitude of the applied EFs. In contrast, our device delivers EFs with a well-characterized radial profile in a noncontacting manner, eliminating conductive heating and enabling thermally regulated EF delivery. To test and demonstrate our system, we generated continuous, 200-kHz EMF with an EF amplitude profile spanning 0-6.5 V/cm pk-pk and applied them to exemplar human thyroid cell cultures for 72 h. We observed moderate reduction in cell density (<10%) at low EF amplitudes (<4 V/cm) and a greater reduction in cell density of up to 25% at higher amplitudes (4-6.5 V/cm). Our device can be readily extended to other EF frequency and amplitude regimes. Future studies with this device should contribute to the ongoing debate about the efficacy and mechanism(s) of action of "TTFields" by better isolating the effects of EFs and providing access to previously inaccessible EF regimes.

Modulation of the Cell Membrane Potential and Intracellular Protein Transport by High Magnetic Fields

To explore cellular responses to high magnetic fields (HMF), we present a model of the interactions of cells with a homogeneous HMF that accounts for the magnetic force exerted on paramagnetic/diamagnetic species. There are various chemical species inside a living cell, many of which may have large concentration gradients. Thus, when an HMF is applied to a cell, the concentration-gradient magnetic forces act on paramagnetic or diamagnetic species and can either assist or oppose large particle movement through the cytoplasm. We demonstrate possibilities for changing the machinery in living cells with HMFs and predict two new mechanisms for modulating cellular functions with HMFs via (i) changes in the membrane potential and (ii) magnetically assisted intracellular diffusiophoresis of large proteins. By deriving a generalized form for the Nernst equation, we find that an HMF can change the membrane potential of the cell and thus have a significant impact on the properties and biological functionality of cells. The elaborated model provides a universal framework encompassing current studies on controlling cell functions by high static magnetic fields. Bioelectromagnetics. 2021;42:27-36. © 2020 Bioelectromagnetics Society.

Intrinsically Magnetic Cells: A Review on Their Natural Occurrence and Synthetic Generation

The magnetization of non-magnetic cells has great potential to aid various processes in medicine, but also in bioprocess engineering. Current approaches to magnetize cells with magnetic nanoparticles (MNPs) require cellular uptake or adsorption through in vitro manipulation of cells. A relatively new field of research is "magnetogenetics" which focuses on in vivo production and accumulation of magnetic material. Natural intrinsically magnetic cells (IMCs) produce intracellular, MNPs, and are called magnetotactic bacteria (MTB). In recent years, researchers have unraveled function and structure of numerous proteins from MTB. Furthermore, protein engineering studies on such MTB proteins and other potentially magnetic proteins, like ferritins, highlight that in vivo magnetization of non-magnetic hosts is a thriving field of research. This review summarizes current knowledge on recombinant IMC generation and highlights future steps that can be taken to succeed in transforming non-magnetic cells to IMCs.

Magnetically-driven 2D cells organization on superparamagnetic micromagnets fabricated by laser direct writing

We demonstrate a proof of concept for magnetically-driven 2D cells organization on superparamagnetic micromagnets fabricated by laser direct writing via two photon polymerization (LDW via TPP) of a photopolymerizable superparamagnetic composite. The composite consisted of a commercially available, biocompatible photopolymer (Ormocore) mixed with 4 mg/mL superparamagnetic nanoparticles (MNPs). The micromagnets were designed in the shape of squares with 70 µm lateral dimension. To minimize the role of topographical cues on the cellular attachment, we fabricated 2D microarrays similar with a chessboard: the superparamagnetic micromagnets alternated with non-magnetic areas of identical shape and lateral size as the micromagnets, made from Ormocore by LDW via TPP. The height difference between the superparamagnetic and non-magnetic areas was of ~ 6 µm. In the absence of a static magnetic field, MNPs-free fibroblasts attached uniformly on the entire 2D microarray, with no preference for the superparamagnetic or non-magnetic areas. Under a static magnetic field of 1.3 T, the fibroblasts attached exclusively on the superparamagnetic micromagnets, resulting a precise 2D cell organization on the chessboard-like microarray. The described method has significant potential for fabricating biocompatible micromagnets with well-defined geometries for building skin grafts adapted for optimum tissue integration, starting from single cell manipulation up to the engineering of whole tissues.

Improving Tumor Retention of Effector Cells in Adoptive Cell Transfer Therapies by Magnetic Targeting

Adoptive cell transfer therapy is a promising anti-tumor immunotherapy in which effector immune cells are transferred to patients to treat tumors. However, one of its main limitations is the inefficient trafficking of inoculated effector cells to the tumor site and the small percentage of effector cells that remain activated when reaching the tumor. Multiple strategies have been attempted to improve the entry of effector cells into the tumor environment, often based on tumor types. It would be, however, interesting to develop a more general approach, to improve and facilitate the migration of specific activated effector lymphoid cells to any tumor type. We and others have recently demonstrated the potential for adoptive cell transfer therapy of the combined use of magnetic nanoparticle-loaded lymphoid effector cells together with the application of an external magnetic field to promote the accumulation and retention of lymphoid cells in specific body locations. The aim of this review is to summarize and highlight the recent findings in the field of magnetic accumulation and retention of effector cells in tumors after adoptive transfer, and to discuss the possibility of using this approach for tumor targeting with chimeric antigen receptor (CAR) T-cells.

Static magnetic field-enhanced osteogenic differentiation of human umbilical cord-derived mesenchymal stem cells via matrix vesicle secretion

METHODS

In methodology, WJMSCs were treated with a 0.4-T SMF. The cell viability was tested using the MTT assay. For the osteogenic analysis, the alkaline phosphatase activity assay and alizarin red S staining were performed. The osteogenic-related gene expression of ALP, BMP-2, and Runx2 was examined using real-time polymerase chain reaction. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy was used to analyze matrix vesicle secretion.

RESULTS

The cell viability showed no significant difference between the SMF-treated group and the sham-exposed cells. However, the SMF-treated group exhibited significantly more mineralized nodule formation and higher ALP activity than their control counterparts (p < .05). The expressions of osteogenic-related markers, ALP, BMP-2, and Runx2, were also significantly higher in the SMF-treated WJMSCs. The scanning electron microscopy results showed much more matrix vesicle secretion in the SMF-treated cells than in the sham-treated cells. A mineralized sheath was noted in the SMF-treated cells, along with a sporadic accumulation of spherical mineralized deposits on the cell surface.

CONCLUSIONS

The results suggest that 0.4-T SMF treatment enhances the osteogenesis of WJMSCs at the early-to-middle stage of osteogenic differentiation by increasing the matrix vesicle secretion and mineralization.

Synthesis of niobium substituted cobalt-nickel nano-ferrite (Co0.5Ni0.5NbxFe2-xO4 (x ≤ 0.1) by hydrothermal approach show strong anti-colon cancer activities

The combination of two or more nanoparticles found to be effective strategy to synthesize nanocomposites for better drug delivery and treatment. In the present study, we have combined cobalt (Co), nickel (Ni), niobium (Nb), and iron oxide (Fe₂O₄) and prepared niobium substituted cobalt-nickel nano-ferrite nanocomposites (Co_0.5Ni_0.5Nb_xFe_2-xO₄ (x ≤ 0.1) by using hydrothermal approach. We have characterized the structure and morphology of nanocomposites by using XRD, EDX, TEM and SEM methodologies. We have examined the impact of nanocomposites (Co_0.5Ni_0.5Nb_xFe_2-xO₄ (x ≤ 0.1) on cancerous cells (human colorectal carcinoma cells, HCT-116) by using MTT assay. We have also checked the impact of nanocomposites on normal and non-cancerous cells (human embryonic kidney cells, HEK-293) to confirm the specificity of their actions. Post- 48 h treatment of Co_0.5Ni_0.5Nb_xFe_2-xO₄ (x ≤ 0.1) led to dose-dependent inhibition of cancer cells growth and proliferation. However, no cytotoxic effect was observed on the normal cells (HEK-293). In addition, DAPI stained nuclear DNA staining analysis demonstrates that the Co_0.5Ni_0.5Nb_xFe_2-xO₄ (x ≤ 0.1) treatment also caused nuclear DNA disintegration which is the marker for programmed cell death. These results demonstrate that synthesized nanocomposites Co_0.5Ni_0.5Nb_xFe_2-xO₄ (x ≤ 0.1) selectively target the colon cancer cells and induce cancer cell death.Communicated by Ramaswamy H. Sarma.

Effect of static magnetic field on DNA synthesis: The interplay between DNA chirality and magnetic field left-right asymmetry

Interactions between magnetic fields (MFs) and living cells may stimulate a large variety of cellular responses to a MF, while the underlying intracellular mechanisms still remain a great puzzle. On a fundamental level, the MF - cell interaction is affected by the two broken symmetries: (a) left-right (LR) asymmetry of the MF and (b) chirality of DNA molecules carrying electric charges and subjected to the Lorentz force when moving in a MF. Here we report on the chirality-driven effect of static magnetic fields (SMFs) on DNA synthesis. This newly discovered effect reveals how the interplay between two fundamental features of symmetry in living and inanimate nature-DNA chirality and the inherent features of MFs to distinguish the left and right-manifests itself in different DNA synthesis rates in the upward and downward SMFs, consequently resulting in unequal cell proliferation for the two directions of the field. The interplay between DNA chirality and MF LR asymmetry will provide fundamental knowledge for many MF-induced biological phenotypes.

MRI safety considerations during pregnancy

The use of magnetic resonance imaging (MRI) during pregnancy is on the rise due its ability to provide detailed cross-sectional anatomy without ionizing radiation. Despite the favorable radiation profile, theoretically concerns regarding the safety of MRI and gadolinium-based contrast agent (GBCA) administration have been raised. Currently there are no studies that have shown any attributable harms of MRI during any trimester of pregnancy although prospective and longitudinal studies are lacking. GBCA administration may be associated with a slightly higher rate of neonatal death, although this is based on a single, large cohort study. Understanding the available evidence regarding MRI safety during pregnancy in the context of current society guidelines will help the radiologist serve as a valuable resource to patients and referring providers.

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.

3D Superparamagnetic Scaffolds for Bone Mineralization under Static Magnetic Field Stimulation

We reported on three-dimensional (3D) superparamagnetic scaffolds that enhanced the mineralization of magnetic nanoparticle-free osteoblast cells. The scaffolds were fabricated with submicronic resolution by laser direct writing via two photons polymerization of Ormocore/magnetic nanoparticles (MNPs) composites and possessed complex and reproducible architectures. MNPs with a diameter of 4.9 ± 1.5 nm and saturation magnetization of 30 emu/g were added to Ormocore, in concentrations of 0, 2 and 4 mg/mL. The homogenous distribution and the concentration of the MNPs from the unpolymerized Ormocore/MNPs composite were preserved after the photopolymerization process. The MNPs in the scaffolds retained their superparamagnetic behavior. The specific magnetizations of the scaffolds with 2 and 4 mg/mL MNPs concentrations were of 14 emu/g and 17 emu/g, respectively. The MNPs reduced the shrinkage of the structures from 80.2 ± 5.3% for scaffolds without MNPs to 20.7 ± 4.7% for scaffolds with 4 mg/mL MNPs. Osteoblast cells seeded on scaffolds exposed to static magnetic field of 1.3 T deformed the regular architecture of the scaffolds and evoked faster mineralization in comparison to unstimulated samples. Scaffolds deformation and extracellular matrix mineralization under static magnetic field (SMF) exposure increased with increasing MNPs concentration. The results are discussed in the frame of gradient magnetic fields of ~3 × 10⁻⁴ T/m generated by MNPs over the cells bodies.

Possible magneto-mechanical and magneto-thermal mechanisms of ion channel activation in magnetogenetics

The palette of tools for perturbation of neural activity is continually expanding. On the forefront of this expansion is magnetogenetics, where ion channels are genetically engineered to be closely coupled to the iron-storage protein ferritin. Initial reports on magnetogenetics have sparked a vigorous debate on the plausibility of physical mechanisms of ion channel activation by means of external magnetic fields. The criticism leveled against magnetogenetics as being physically implausible is based on the specific assumptions about the magnetic spin configurations of iron in ferritin. I consider here a wider range of possible spin configurations of iron in ferritin and the consequences these might have in magnetogenetics. I propose several new magneto-mechanical and magneto-thermal mechanisms of ion channel activation that may clarify some of the mysteries that presently challenge our understanding of the reported biological experiments. Finally, I present some additional puzzles that will require further theoretical and experimental investigation.

Molecular orbitals of delocalized electron clouds in neuronal domains

We have further developed the two-brains hypothesis as a form of complementarity (or complementary relationship) of endogenously induced weak magnetic fields in the electromagnetic brain. The locally induced magnetic field between electron magnetic dipole moments of delocalized electron clouds in neuronal domains is complementary to the exogenous electromagnetic waves created by the oscillating molecular dipoles in the electro-ionic brain. In this paper, we mathematically model the operation of the electromagnetic grid, especially in regard to the functional role of atomic orbitals of dipole-bound delocalized electrons. A quantum molecular dynamic approach under quantum equilibrium conditions is taken to illustrate phase differences between quasi-free electrons tethered to an oscillating molecular core. We use a simplified version of the many-body problem to analytically solve the macro-quantum wave equation (equivalent to the Kohn-Sham equation). The resultant solution for the mechanical angular momentum can be used to approximate the molecular orbital of the dipole-bound delocalized electrons. In addition to non-adiabatic motion of the molecular core, 'guidance waves' may contribute to the delocalized macro-quantum wave functions in generating nonlocal phase correlations. The intrinsic magnetic properties of the origins of the endogenous electromagnetic field are considered to be a nested hierarchy of electromagnetic fields that may also include electromagnetic patterns in three-dimensional space. The coupling between the two-brains may involve an 'anticipatory affect' based on the conceptualization of anticipation as potentiality, arising either from the macro-quantum potential energy or from the electrostatic effects of residual charges in the quantum and classical subsystems of the two-brains that occurs through partitioning of the potential energy of the combined quantum molecular dynamic system.

Magnetic Silicium Hydroxyapatite Nanorods for Enhancing Osteoblast Response in Vitro and Biointegration in Vivo

Osteoblast behavior playing an important role in the biointegration of the Ti implant with host bone in vivo can be regulated by surface properties and magnetic field. In order to endow the Ti surface with good osteogenesis activity, Si monosubstituted and Fe and Si cosubstituted hydroxyapatite (HAp) nanorods were fabricated on microporous TiO₂ by microarc oxidation (MAO) followed with hydrothermal treatment (HT). The surface properties including microstructure, microroughness, hydrophilicity, ion release, magnetic property, cytocompatibility, and biointegration of substituted HAp nanorods were observed and evaluated, together with pure HAp nanorods and microarc oxidated (MAOed) TiO₂ as controls. After being doped with Fe, MAOed TiO₂ has no changes in phase composition and microroughness, whereas it displays weakly ferromagnetic behavior and can enhance osteoblast differentiation in vitro and formation of new bone in vivo, compared with the undoped one. The substituted HAp nanorods adhere firmly to TiO₂ and have almost the same wettability and microroughness but additional Si, Fe, and/or Ca released into the medium, compared with pure HAp nanorods. Moreover, the cosubstituted HAp has a small ferromagnetic signal, while its saturation magnetization value is less than that of the MAOed doped with Fe. Compared to pure HA nanorods, the substituted HAp nanorods not only improve cell proliferation and differentiation in vitro, but also enhance the ability of bone integration in vivo, especially for the cosubstituted one, which should be ascribed to the combined effect of microstructure, magnetic property, and released ions.

Efficacy of pulsed electromagnetic fields and electromagnetic fields tuned to the ion cyclotron resonance frequency of Ca2+ on chondrogenic differentiation

Previous studies provide strong evidence for the therapeutic effect of electromagnetic fields (EMFs) on different tissues including cartilage. Diverse exposure parameters applied in scientific reports and the unknown interacting mechanism of EMF with biological systems make EMF studies challenging. In 1985, Liboff proposed that when magnetic fields are tuned to the cyclotron resonance frequencies of critical ions, the motion of ions through cell membranes is enhanced, and thus biological effects appear. Such exposure system consists of a weak alternating magnetic field (B₁ ) in the presence of a static magnetic field (B₀ ) and depends on the relationship between the magnitudes of B₀ and B₁ and the angular frequency Ω. The purpose of the present study is to determine the chondrogenic potential of EMF with regards to pulsed EMF (PEMF) and the ion cyclotron resonance (ICR) theory. We used different stimulating systems to generate EMFs in which cells are either stimulated with ubiquitous PEMF parameters, frequently reported, or parameters tuned to satisfy the ICR for Ca²⁺ (including negative and positive control groups). Chondrogenesis was analysed after 3 weeks of treatment. Cell stimulation under the ICR condition showed positive results in the context of glycosaminoglycans and type II collagen synthesis. In contrast, the other electromagnetically stimulated groups showed no changes compared with the control groups. Furthermore, gene expression assays revealed an increase in the expression of chondrogenic markers (COL2A1, SOX9, and ACAN) in the ICR group. These results suggest that the Ca²⁺ ICR condition can be an effective factor in inducing chondrogenesis.

Effects of extremely low-frequency electromagnetic fields on B16F10 cancer cells

This paper presents a method to inhibit B16F10 cancer cells using extremely low-frequency electromagnetic fields (ELF-EMFs) and to evaluate cell viability using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The study examined the effect of a natural EMF resonance frequency (7.83 Hz) and a power line frequency (60 Hz) on B16F10 cancer cells for 24 and 48 h. The B16F10 cancer cells were also exposed to sweep frequencies in several sweep intervals to quantitatively analyze the viability of cancer cells. The results yielded a 17% inhibition rate under 7.83 Hz compared with that of the control group. Moreover, sweep frequencies in narrow intervals (7.83 ± 0.1 Hz for the step 0.05 Hz) caused an inhibition rate of 26.4%, and inhibitory effects decreased as frequency sweep intervals increased. These results indicate that a Schumann resonance frequency of 7.83 Hz can inhibit the growth of cancer cells and that using a specific frequency type can lead to more effective growth inhibition.

T cells loaded with magnetic nanoparticles are retained in peripheral lymph nodes by the application of a magnetic field

Background

T lymphocytes are highly dynamic elements of the immune system with a tightly regulated migration. T cell-based transfer therapies are promising therapeutic approaches which in vivo efficacy is often limited by the small proportion of administered cells that reaches the region of interest. Manipulating T cell localisation to improve specific targeting will increase the effectiveness of these therapies. Nanotechnology has been successfully used for localized release of drugs and biomolecules. In particular, magnetic nanoparticles (MNPs) loaded with biomolecules can be specifically targeted to a location by an external magnetic field (EMF). The present work studies whether MNP-loaded T cells could be targeted and retained in vitro and in vivo at a site of interest with an EMF.

Results

T cells were unable to internalize the different MNPs used in this study, which remained in close association with the cell membrane. T cells loaded with an appropriate MNP concentration were attracted to an EMF and retained in an in vitro capillary flow-system. MNP-loaded T cells were also magnetically retained in the lymph nodes after adoptive transfer in in vivo models. This enhanced in vivo retention was in part due to the EMF application and to a reduced circulating cell speed within the organ. This combined use of MNPs and EMFs did not alter T cell viability or function.

Conclusions

These studies reveal a promising approach to favour cell retention that could be implemented to improve cell-based therapy.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0440-z) contains supplementary material, which is available to authorized users.

Role of nuclear mechanosensitivity in determining cellular responses to forces and biomaterials

Tissue engineers use biomaterials or apply forces to alter cell behaviors and cure damaged/diseased tissues. The external physical cues perceived by cells are transduced intracellularly along the mechanosensitive machineries, including subcellular adhesion molecules and cytoskeletons. The signals are further channeled to a nucleus through the physical links of nucleoskeleton and cytoskeleton or the biochemical translocation of transcription factors. Thus, the external cues are thought to affect directly or indirectly the nucleus and the genetic transcriptional process, ultimately determining cell fate. Here we communicate the importance of such mechanotransductory processes in cell and tissue engineering where external forces- or biomaterials-related physical cues essentially regulate cellular behaviors, with an emphasis on the mechanosensing and signaling along the road to a nucleus.

Biomechanical studies on biomaterial degradation and co-cultured cells: mechanisms, potential applications, challenges and prospects

This review provides a comprehensive overview of biomechanical studies on biomaterial degradation and co-cultured cells as well as valuable biomechanical ideas on how to design or optimize cell biomaterial co-culture system.

A superparamagnetic Fe3O4–TiO2 composite coating on titanium by micro-arc oxidation for percutaneous implants

The micro-magnetic field induced by the Fe₃O₄ nanoparticles in TiO₂ can efficiently enhance the fibroblast response, reduce bacterial reproduction in vitro, and improve skin integration in vivo.

A Critical Review on Selected External Physical Cues and Modulation of Cell Behavior: Magnetic Nanoparticles, Non-thermal Plasma and Lasers

Physics-based biomedical approaches have proved their importance for the advancement of medical sciences and especially in medical diagnostics and treatments. Thus, the expectations regarding development of novel promising physics-based technologies and tools are very high. This review describes the latest research advances in biomedical applications of external physical cues. We overview three distinct topics: using high-gradient magnetic fields in nanoparticle-mediated cell responses; non-thermal plasma as a novel bactericidal agent; highlights in understanding of cellular mechanisms of laser irradiation. Furthermore, we summarize the progress, challenges and opportunities in those directions. We also discuss some of the fundamental physical principles involved in the application of each cue. Considerable technological success has been achieved in those fields. However, for the successful clinical translation we have to understand the limitations of technologies. Importantly, we identify the misconceptions pervasive in the discussed fields.

Intrinsically ferromagnetic Fe-doped TiO2 coatings on titanium for accelerating osteoblast response in vitro

The microenvironment can regulate osteoblast behavior during integration of implants with host bones. An intrinsically magnetic field induced by an Fe³⁺ doped TiO₂ coating was applied herein to enhance the cytocompatibility of Ti. Porous TiO₂ incorporated with different amounts of Fe (2.27-11.07 wt%) was directly prepared on Ti by micro-arc oxidation. The microstructure, roughness, wettability, ion releasing and magnetic property of TiO₂ coatings were investigated. Cell behavior, including adhesion, proliferation, differentiation, collagen secretion and extracellular matrix mineralization on coating surfaces was evaluated. The results show that incorporation of Fe³⁺ did not significantly alter the phase component, topography, roughness and wettability of coatings, and with increased doses of Fe³⁺, trace amounts of Fe³⁺ were released into the media, whereas the Ca²⁺ accumulation concentration slightly decreased. Fe-Doped TiO₂ displayed a weak ferromagnetic property, and its saturation magnetization value increased initially and then decreased with the increased dose of Fe. Compared with the undoped, proliferation, expression of osteogenesis-related genes, collagen secretion and extracellular matrix mineralization of osteoblasts were enhanced with Fe doped ones, especially for those with 4.25 wt% Fe. By analyzing the structures and properties of different surfaces and their osteoblast responses, it is deduced that the ferromagnetism of Fe doped TiO₂ plays a key role in enhancing osteoblast behavior. Such a result provides a new perspective for the potential application of ferromagnetic coatings in bone repair.

Magnetophoretic lensing by concentric topographic cylinders of perpendicular magnetic anisotropy multilayers

Colloidal magnetophoretic lensing of water suspended micrometer-sized superparamagnetic beads (SPBs) above a topographically patterned magnetic thin film system with perpendicular magnetic anisotropy is demonstrated. The magnetic pattern consisting of concentric annuli of micron-sized widths has been superimposed with a rotating external magnetic field, and it is shown that the trajectories of the SPBs above this structure are similar to light rays in an optical focusing lens. SPB trajectories converge towards the central region and have divergent trajectories while passing the center. The experimental findings are corroborated by a quantitative model for the SPB trajectories. The magnetophoretic lensing effect leads to a high SPB concentration in the center of the pattern and may be useful for applications where SPBs have to approach each other in a controlled way.

Use of 0.4-Tesla static magnetic field to promote reparative dentine formation of dental pulp stem cells through activation of p38 MAPK signalling pathway

AIM

To investigate whether static magnetic fields (SMFs) have a positive effect on the migration and dentinogenesis of dental pulp stem cells (DPSCs) to promote reparative dentine formation.

METHODOLOGY

In vitro scratch assays and a traumatic pulp exposure model were performed to evaluate the effect of 0.4-Tesla (T) SMF on DPSC migration. The cytoskeletons of the DPSCs were identified by fluorescence immunostaining and compared with those of a sham-exposed group. Dentinogenic evaluation was performed by analysing the expressions of DMP-1 and DSPP marker genes using a quantitative real-time polymerase chain reaction (qRT-PCR) process. Furthermore, the formation of calcified deposits was examined by staining the dentinogenic DPSCs with Alizarin Red S dye. Finally, the role played by the p38 MAPK signalling pathway in the migration and dentinogenesis of DPSCs under 0.4-T SMF was investigated by incorporating p38 inhibitor (SB203580) into the in vitro DPSC experiments. The Student's t-test and the Kruskal-Wallis test followed by Dunn's post hoc test with a significance level of P < 0.05 were used for statistical analysis.

RESULTS

The scratch assay results revealed that the application of 0.4-T SMF enhanced DPSCs migration towards the scratch wound (P < 0.05). The cytoskeletons of the SMF-treated DPSCs were found to be aligned perpendicular to the scratch wound. After 20 days of culture, the SMF-treated group had a greater number of out-grown cells than the sham-exposed group (nonmagnetized control). For the SMF-treated group, the DMP-1 (P < 0.05) and DSPP genes (P < 0.05), analysed by qRT-PCR, exhibited a higher expression. The distribution of calcified nodules was also found to be denser in the SMF-treated group when stained with Alizarin Red S dye (P < 0.05). Given the incorporation of p38 inhibitor SB203580 into the DPSCs, cell migration and dentinogenesis were suppressed. No difference was found between the SMF-treated and sham-exposed cells (P > 0.05).

CONCLUSION

0.4-T SMF enhanced DPSC migration and dentinogenesis through the activation of the p38 MAPK-related pathway.

Cells in the Non-Uniform Magnetic World: How Cells Respond to High-Gradient Magnetic Fields

Imagine cells that live in a high-gradient magnetic field (HGMF). Through what mechanisms do the cells sense a non-uniform magnetic field and how such a field changes the cell fate? We show that magnetic forces generated by HGMFs can be comparable to intracellular forces and therefore may be capable of altering the functionality of an individual cell and tissues in unprecedented ways. We identify the cellular effectors of such fields and propose novel routes in cell biology predicting new biological effects such as magnetic control of cell-to-cell communication and vesicle transport, magnetic control of intracellular ROS levels, magnetically induced differentiation of stem cells, magnetically assisted cell division, or prevention of cells from dividing. On the basis of experimental facts and theoretical modeling we reveal timescales of cellular responses to high-gradient magnetic fields and suggest an explicit dependence of the cell response time on the magnitude of the magnetic field gradient.

Effects of large gradient high magnetic field (LG-HMF) on the long-term culture of aquatic organisms: Planarians example

Large gradient high magnetic field (LG-HMF) is a powerful tool to study the effects of altered gravity on organisms. In our study, a platform for the long-term culture of aquatic organisms was designed based on a special superconducting magnet with an LG-HMF, which can provide three apparent gravity levels (µ g, 1 g, and 2 g), along with a control condition on the ground. Planarians, Dugesia japonica, were head-amputated and cultured for 5 days in a platform for head reconstruction. After planarian head regeneration, all samples were taken out from the superconducting magnet for a behavioral test under geomagnetic field and normal gravity conditions. To analyze differences among the four groups, four aspects of the planarians were considered, including head regeneration rate, phototaxis response, locomotor velocity, and righting behavior. Data showed that there was no significant difference in the planarian head regeneration rate under simulated altered gravity. According to statistical analysis of the behavioral test, all of the groups had normal functioning of the phototaxis response, while the planarians that underwent head reconstruction under the microgravity environment had significantly slower locomotor velocity and spent more time in righting behavior. Furthermore, histological staining and immunohistochemistry results helped us reveal that the locomotor system of planarians was affected by the simulated microgravity environment. We further demonstrated that the circular muscle of the planarians was weakened (hematoxylin and eosin staining), and the epithelial cilia of the planarians were reduced (anti-acetylated tubulin staining) under the simulated microgravity environment. Bioelectromagnetics. 2018;39:428-440. © 2018 Wiley Periodicals, Inc.