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To assess cell death pathways in response to magnetic hyperthermia. Human melanoma cells were loaded with citric acid-coated iron-oxide nanoparticles, and subjected to a time-varying magnetic field. Pathways were monitored in suspensions and in monolayers using fluorophores to report on early-stage apoptosis and late-stage apoptosis and/or necrosis. Delayed-onset effects were observed, with a rate and extent proportional to the thermal-load-per-cell. At moderate loads, membranal internal-to-external lipid exchange preceded rupture and death by a few hours (the timeline varying cell-to-cell), without any measurable change in the local environment temperature. Our observations support the proposition that intracellular heating may be a viable, controllable and nonaggressive treatment for human pathological conditions.

Breast cancer staging with sentinel lymph node biopsy relies on the use of radioisotopes, which limits the availability of the procedure worldwide. The use of a magnetic nanoparticle tracer and a handheld magnetometer provides a radiation-free alternative, which was recently evaluated in two clinical trials. The hydrodynamic particle size of the used magnetic tracer differs substantially from the radioisotope tracer and could therefore benefit from optimization. The aim of this study was to assess the performance of three different-sized magnetic nanoparticle tracers for sentinel lymph node biopsy within an in vivo porcine model. Sentinel lymph node biopsy was performed within a validated porcine model using three magnetic nanoparticle tracers, approved for use in humans (ferumoxytol, with hydrodynamic diameter d H =32 nm; Sienna+(®), d H =59 nm; and ferumoxide, d H =111 nm), and a handheld magnetometer. Magnetometer counts (transcutaneous and ex vivo), iron quantification (vibrating sample magnetometry), and histopathological assessments were performed on all ex vivo nodes. Transcutaneous \"hotspots\" were present in 12/12 cases within 30 minutes of injection for the 59 nm tracer, compared to 7/12 for the 32 nm tracer and 8/12 for the 111 nm tracer, at the same time point. Ex vivo magnetometer counts were significantly greater for the 59 nm tracer than for the other tracers. Significantly more nodes per basin were excised for the 32 nm tracer compared to other tracers, indicating poor retention of the 32 nm tracer. Using the 59 nm tracer resulted in a significantly higher iron accumulation compared to the 32 nm tracer. The 59 nm tracer demonstrated rapid lymphatic uptake, retention in the first nodes reached, and accumulation in high concentration, making it the most suitable tracer for intraoperative sentinel lymph node localization.

Magnetic hyperthermia - a potential cancer treatment in which superparamagnetic iron oxide nanoparticles (SPIONs) are made to resonantly respond to an alternating magnetic field (AMF) and thereby produce heat - is of significant current interest. We have previously shown that mesenchymal stem cells (MSCs) can be labeled with SPIONs with no effect on cell proliferation or survival and that within an hour of systemic administration, they migrate to and integrate into tumors in vivo. Here, we report on some longer term (up to 3 weeks) post-integration characteristics of magnetically labeled human MSCs in an immunocompromized mouse model. We initially assessed how the size and coating of SPIONs dictated the loading capacity and cellular heating of MSCs. Ferucarbotran(®) was the best of those tested, having the best like-for-like heating capability and being the only one to retain that capability after cell internalization. A mouse model was created by subcutaneous flank injection of a combination of 0.5 million Ferucarbotran-loaded MSCs and 1.0 million OVCAR-3 ovarian tumor cells. After 2 weeks, the tumors reached ~100 µL in volume and then entered a rapid growth phase over the third week to reach ~300 µL. In the control mice that received no AMF treatment, magnetic resonance imaging (MRI) data showed that the labeled MSCs were both incorporated into and retained within the tumors over the entire 3-week period. In the AMF-treated mice, heat increases of ~4°C were observed during the first application, after which MRI indicated a loss of negative contrast, suggesting that the MSCs had died and been cleared from the tumor. This post-AMF removal of cells was confirmed by histological examination and also by a reduced level of subsequent magnetic heating effect. Despite this evidence for an AMF-elicited response in the SPION-loaded MSCs, and in contrast to previous reports on tumor remission in immunocompetent mouse models, in this case, no significant differences were measured regarding the overall tumor size or growth characteristics. We discuss the implications of these results on the clinical delivery of hyperthermia therapy to tumors and on the possibility that a preferred therapeutic route may involve AMF as an adjuvant to an autologous immune response.

There is a growing interest in exploring the therapeutically mediated modulation of tumor vascularization of pancreatic cancer, which is known for its poorly perfused tumor microenvironment limiting the delivery of therapeutic agents to the tumor site. Here, we assessed how magnetic hyperthermia in combination with chemotherapy selectively affects growth, the vascular compartment of tumors, and the presence of tumor cells expressing key regulators of angiogenesis. To that purpose, a orthotopic PANC-1 (fluorescent human pancreatic adenocarcinoma) mouse tumor model (Rj:Athym-Foxn1nu/nu) was used. Magnetic hyperthermia was applied alone or in combination with systemic chemotherapy (gemcitabine 50 mg per kg body weight, nab-pacitaxel 30 mg/kg body weight) on days 1 and 7 following magnetic nanoparticle application (dose: 1 mg per 100 mm3 of tumor). We used ultrasound imaging, immunohistochemistry, multi-spectral optoacoustic tomography (MSOT), and hematology to assess the biological parameters mentioned above. We found that magnetic hyperthermia in combination with gemcitabine/paclitaxel chemotherapy was able to impact tumor growth (decreased volumes and Ki67 expression) and to trigger neo-angiogenesis (increased small vessel diameter) as a result of the therapeutically mediated cell damages/stress in tumors. The applied stressors activated specific pro-angiogenic mechanisms, which differed from those seen in hypoxic conditions involving HIF-1α, since (a) treated tumors showed a significant decrease of cells expressing VEGF, CD31, HIF-1α, and neuropilin-1; and (b) the relative tumor blood volume and oxygen level remained unchanged. Neo-angiogenesis seems to be the result of the activation of cell stress pathways, like MAPK pathways (high number of pERK-expressing tumor cells). In the long term, the combination of magnetic hyperthermia and chemotherapy could potentially be applied to transiently modulate tumor angiogenesis and to improve drug accessibility during oncologic therapies of pancreatic cancer.

Astrocytes play crucial and diverse roles in brain health and disease. The ability to selectively control astrocytes provides a valuable tool for understanding their function and has the therapeutic potential to correct dysfunction. Existing technologies such as optogenetics and chemogenetics require the introduction of foreign proteins, which adds a layer of complication and hinders their clinical translation. A novel technique, magnetomechanical stimulation (MMS), that enables remote and selective control of astrocytes without genetic modification is described here. MMS exploits the mechanosensitivity of astrocytes and triggers mechanogated Ca2+ and adenosine triphosphate (ATP) signaling by applying a magnetic field to antibody‐functionalized magnetic particles that are targeted to astrocytes. Using purpose‐built magnetic devices, the mechanosensory threshold of astrocytes is determined, a sub‐micrometer particle for effective MMS is identified, the in vivo fate of the particles is established, and cardiovascular responses are induced in rats after particles are delivered to specific brainstem astrocytes. By eliminating the need for device implantation and genetic modification, MMS is a method for controlling astroglial activity with an improved prospect for clinical application than existing technologies. Magnetomechanical stimulation (MMS) is a novel technology that enables remote and selective control of brain cell activity without any need for genetic modification or device implantation. Antibody‐functionalized magnetic particles are targeted to the mechanosensitive astrocytes and a magnetic field is applied to activate Ca2+ and adenosine triphosphate (ATP) signaling that regulate a wide range of physiological, cognitive, and behavioral processes.

Medical therapies achieve their control at expense to the patient in the form of a range of toxicities, which incur costs and diminish quality of life. Magnetic resonance navigation is an emergent technique that enables image‐guided remote‐control of magnetically labeled therapies and devices in the body, using a magnetic resonance imaging (MRI) system. Minimally INvasive IMage‐guided Ablation (MINIMA), a novel, minimally invasive, MRI‐guided ablation technique, which has the potential to avoid traditional toxicities, is presented. It comprises a thermoseed navigated to a target site using magnetic propulsion gradients generated by an MRI scanner, before inducing localized cell death using an MR‐compatible thermoablative device. The authors demonstrate precise thermoseed imaging and navigation through brain tissue using an MRI system (0.3 mm), and they perform thermoablation in vitro and in vivo within subcutaneous tumors, with the focal ablation volume finely controlled by heating duration. MINIMA is a novel theranostic platform, combining imaging, navigation, and heating to deliver diagnosis and therapy in a single device. Minimally invasive image‐guided ablation is a novel therapy that uses a magnetic resonance imaging (MRI) scanner to deliver precise focal ablation therapy. A ferromagnetic thermoseed is navigated to the target using the magnetic field gradients generated by the MRI scanner and then heated using an MR‐compatible radiofrequency coil to deliver localized thermoablation.

Background Sentinel lymph node biopsy (SLNB) in melanoma is currently performed using the standard dual technique (radioisotope and blue dye). The magnetic technique is non-radioactive and provides a brown color change in the sentinel lymph node (SLN) through an intradermal injection of a magnetic tracer, and utilizes a handheld magnetometer. The MELAMAG Trial compared the magnetic technique with the standard technique for SLNB in melanoma. Methods Clinically node-negative patients with primary cutaneous melanoma were recruited from four centers. SLNB was undertaken after intradermal administration of both the standard (blue dye and radioisotope) and magnetic tracers. The SLN identification rate per patient, with the two techniques, was compared. Results A total of 133 patients were recruited, 129 of which were available for final analysis. The sentinel node identification rate was 97.7 % (126/129) with the standard technique and 95.3 % (123/129) with the magnetic technique [2.3 % difference; 95 % upper confidence limit (CL) 6.4; 5.4 % discordance]. With radioisotope alone, the SLN identification rate was 95.3 % (123/129), as with the magnetic technique (0 % difference; 95 % upper CL 4.5; 7.8 % discordance). The lymph node retrieval rate was 1.99 nodes per patient overall, 1.78 with the standard technique and 1.87 with the magnetic technique. Conclusions The magnetic technique is feasible for SLNB in melanoma with a high SLN identification rate, but is associated with skin staining. When compared with the standard dual technique, it did not reach our predefined non-inferiority margin.

Drug delivery to the gastrointestinal (GI) tract is highly challenging due to the harsh environments any drug- delivery vehicle must experience before it releases it’s drug payload. Effective targeted drug delivery systems often rely on external stimuli to effect release, therefore knowing the exact location of the capsule and when to apply an external stimulus is paramount. We present a drug delivery system for the GI tract based on coating standard gelatin drug capsules with a model eicosane- superparamagnetic iron oxide nanoparticle composite coating, which is activated using magnetic hyperthermia as an on-demand release mechanism to heat and melt the coating. We also show that the capsules can be readily detected via rapid X-ray computed tomography (CT) and magnetic resonance imaging (MRI), vital for progressing such a system towards clinical applications. This also offers the opportunity to image the dispersion of the drug payload post release. These imaging techniques also influenced capsule content and design and the delivered dosage form. The ability to easily change design demonstrates the versatility of this system, a vital advantage for modern, patient-specific medicine.

Consider a single agent capable of diagnosing cancer, treating it simultaneously and monitoring response to treatment. Particles of this agent would seek cancer cells accurately and destroy them without harming normal surrounding cells. Science fiction or reality? Nanotechnology and nanomedicine are rapidly growing fields that encompass the creation of materials and devices at atomic, molecular and supramolecular level, for potential clinical use. Advances in nanotechnology are bringing us closer to the development of dual and multi-functional nanoparticles that are challenging the traditional distinction between diagnostic and treatment agents. Examples include contrast agents capable of delivering targeted drugs to specific epithelial receptors. This opens the way for targeted chemotherapy which could minimise systemic side-effects, avoid damage to benign tissues and also reduce the therapeutic treatment dose of a drug required. Most of the current research is still at the pre-clinical stage, with very few instances of bench to bedside research. In order to encourage more translational research, a fundamental change is required to consider the current clinical challenges and then look at ways in which nanotechnology can address these.

Minimally Invasive Image‐Guided Ablation Concept An artist's impression of the minimally invasive image‐guided ablation (MINIMA) concept, whereby the magnetic field gradients generated by an MRI scanner are used to navigate a ferromagnetic thermoseed through tissue to a target, where it is remotely heated to deliver thermal ablation. More details can be found in article number 2105333 by Rebecca R. Baker, Mark F. Lythgoe, and co‐workers.