Optimal Halbach Permanent Magnet Designs for Maximally Pulling and Pushing Nanoparticles

Compact remanence-free permanent magnet-based variable magnetic field source

We demonstrate a simple and compact variable magnetic field source based on the permanent cube magnet array approximating a Halbach cylinder. The large air gap area accommodates standard cryostat tails while providing a high uniformity and magnetic field stability of up to 0.5 T over regions of up to about a centimeter. It eliminates magnetic remanence effects and produces reproducible fields without the need for feedback. Thanks to the low cost and exceptional energy efficiency, it provides an accessible solution for modest magnetic field requirements in a wide range of research applications.

Low-field NMR with multilayer Halbach magnet and NMR selective excitation

This study introduces a low-field NMR spectrometer (LF-NMR) featuring a multilayer Halbach magnet supported by a combined mechanical and electrical shimming system. This setup offers improved field homogeneity and sensitivity compared to spectrometers relying on typical Halbach and dipole magnets. The multilayer Halbach magnet was designed and assembled using three nested cylindrical magnets, with an additional inner Halbach layer that can be rotated for mechanical shimming. The coils and shim-kernel of the electrical shimming system were constructed and coated with layers of zirconia, thermal epoxy, and silver-paste resin to facilitate passive heat dissipation and ensure mechanical and thermal stability. Furthermore, the 7-channel shim coils were divided into two parts connected in parallel, resulting in a reduction of joule heating temperatures from 96.2 to 32.6 °C. Without the shimming system, the Halbach magnet exhibits a field inhomogeneity of approximately 140 ppm over the sample volume. The probehead was designed to incorporate a solenoidal mini coil, integrated into a single planar board. This design choice aimed to enhance sensitivity, minimize [Formula: see text] inhomogeneity, and reduce impedance discrepancies, transmission loss, and signal reflections. Consequently, the resulting linewidth of water within a 3 mm length and 2.4 mm inner diameter sample volume was 4.5 Hz. To demonstrate the effectiveness of spectral editing in LF-NMR applications at 29.934 MHz, we selectively excited hydroxyl and/or methyl protons in neat acetic acid using optimal control pulses calculated through the Krotov algorithm.

3D-Printed Replica and Porcine Explants for Pre-Clinical Optimization of Endoscopic Tumor Treatment by Magnetic Targeting

Simple Summary

Animal models are often needed in cancer research but some research questions may be answered with other models, e.g., 3D replicas of patient-specific data, as these mirror the anatomy in more detail. We, therefore, developed a simple eight-step process to fabricate a 3D replica from computer tomography (CT) data using solely open access software and described the method in detail. For evaluation, we performed experiments regarding endoscopic tumor treatment with magnetic nanoparticles by magnetic hyperthermia and local drug release. For this, the magnetic nanoparticles need to be accumulated at the tumor site via a magnetic field trap. Using the developed eight-step process, we printed a replica of a locally advanced pancreatic cancer and used it to find the best position for the magnetic field trap. In addition, we described a method to hold these magnetic field traps stably in place. The results are highly important for the development of endoscopic tumor treatment with magnetic nanoparticles as the handling and the stable positioning of the magnetic field trap at the stomach wall in close proximity to the pancreatic tumor could be defined and practiced. Finally, the detailed description of the workflow and use of open access software allows for a wide range of possible uses.

Abstract

Background: Animal models have limitations in cancer research, especially regarding anatomy-specific questions. An example is the exact endoscopic placement of magnetic field traps for the targeting of therapeutic nanoparticles. Three-dimensional-printed human replicas may be used to overcome these pitfalls. Methods: We developed a transparent method to fabricate a patient-specific replica, allowing for a broad scope of application. As an example, we then additively manufactured the relevant organs of a patient with locally advanced pancreatic ductal adenocarcinoma. We performed experimental design investigations for a magnetic field trap and explored the best fixation methods on an explanted porcine stomach wall. Results: We describe in detail the eight-step development of a 3D replica from CT data. To guide further users in their decisions, a morphologic box was created. Endoscopies were performed on the replica and the resulting magnetic field was investigated. The best fixation method to hold the magnetic field traps stably in place was the fixation of loops at the stomach wall with endoscopic single-use clips. Conclusions: Using only open access software, the developed method may be used for a variety of cancer-related research questions. A detailed description of the workflow allows one to produce a 3D replica for research or training purposes at low costs.

Magnetic particle targeting for diagnosis and therapy of lung cancers

Over the past decade, the growing interest in targeted lung cancer therapy has guided researchers toward the cutting edge of controlled drug delivery, particularly magnetic particle targeting. Targeting of tissues by magnetic particles has tackled several limitations of traditional drug delivery methods for both cancer detection (e.g., using magnetic resonance imaging) and therapy. Delivery of magnetic particles offers the key advantage of high efficiency in the local deposition of drugs in the target tissue with the least harmful effect on other healthy tissues. This review first overviews clinical aspects of lung morphology and pathogenesis as well as clinical features of lung cancer. It is followed by reviewing the advances in using magnetic particles for diagnosis and therapy of lung cancers: (i) a combination of magnetic particle targeting with MRI imaging for diagnosis and screening of lung cancers, (ii) magnetic drug targeting (MDT) through either intravenous injection and pulmonary delivery for lung cancer therapy, and (iii) computational simulations that models new and effective approaches for magnetic particle drug delivery to the lung, all supporting improved lung cancer treatment. The review further discusses future opportunities to improve the clinical performance of MDT for diagnosis and treatment of lung cancer and highlights clinical therapy application of the MDT as a new horizon to cure with minimal side effects a wide variety of lung diseases and possibly other acute respiratory syndromes (COVID-19, MERS, and SARS).

A bionic shuttle carrying multi-modular particles and holding tumor-tropic features

The systemic delivery of composite nanoparticles remains an outstanding challenge in cancer nanomedicine, and the principal reason is a complex interplay of biological barriers. In this regard, adaptive cell transfer may represent an alternative solution to circumvent these barriers down to the tumor microenvironment. Here, tumor-tropic macrophages are proposed as a tool to draw and vehiculate modular nanoparticles integrating magnetic and plasmonic components. The end result is a bionic shuttle that exhibits a plasmonic band within the so-called therapeutic window arising from as much as 40 pg Au per cell, magnetization in the order of 150 pemu per cell, and more than 90% of the pristine viability and chemotactic activity of its biological component, until at least two days of preparation. Its synergistic combination of plasmonic, magnetic and tumor-tropic functions is assessed in vitro for applications as magnetic guidance or sorting, with a propulsion around 4 μm s^-1 for a magnetic gradient of 0.8 T m^-1, the optical hyperthermia of cancer, with stability of photothermal conversion to temperatures exceeding 50^∘C, and the photoacoustic imaging of cancer under realistic conditions. These results collectively suggest that a bionic design may be a promising roadmap to reconcile the efforts for multifunctionality and targeted delivery, which are both key goals in nanomedicine.

Rotating Magnetic Nanoparticle Clusters as Microdevices for Drug Delivery

BACKGROUND

Magnetic nanoparticles (MNPs) hold promise for enhancing delivery of therapeutic agents, either through direct binding or by functioning as miniature propellers. Fluid-filled conduits and reservoirs within the body offer avenues for MNP-enhanced drug delivery. MNP clusters can be rotated and moved across surfaces at clinically relevant distances in response to a rotating magnet. Limited data are available regarding issues affecting MNP delivery by this mechanism, such as adhesion to a cellular wall. Research reported here was initiated to better understand the fundamental principles important for successful implementation of rotational magnetic drug targeting (rMDT).

METHODS

Translational movements of four different iron oxide MNPs were tested, in response to rotation (3 Hz) of a neodymium-boron-iron permanent magnet. MNP clusters moved along biomimetic channels of a custom-made acrylic tray, by surface walking. The effects of different distances and cellular coatings on MNP velocity were analyzed using videography. Dyes (as drug surrogates) and the drug etoposide were transported by rotating MNPs along channels over a 10 cm distance.

RESULTS

MNP translational velocities could be predicted from magnetic separation times. Changes in distance or orientation from the magnet produced alterations in MNP velocities. Mean velocities of the fastest MNPs over HeLa, U251, U87, and E297 cells were 0.24 ± 0.02, 0.26 ± 0.02, 0.28 ± 0.01, and 0.18 ± 0.03 cm/sec, respectively. U138 cells showed marked MNP adherence and an 87.1% velocity reduction at 5.5 cm along the channel. Dye delivery helped visualize the effects of MNPs as microdevices for drug delivery. Dye delivery by MNP clusters was 21.7 times faster than by diffusion. MNPs successfully accelerated etoposide delivery, with retention of chemotherapeutic effect.

CONCLUSION

The in vitro system described here facilitates side-by-side comparisons of drug delivery by rotating MNP clusters, on a human scale. Such microdevices have the potential for augmenting drug delivery in a variety of clinical settings, as proposed.

Pushing of Magnetic Microdroplet Using Electromagnetic Actuation System

Treatment of certain diseases requires the administration of drugs at specific areas of tissues and/or organs to increase therapy effectiveness and avoid side effects that may harm the rest of the body. Drug targeting is a research field that uses various techniques to administrate therapies at specific areas of the body, including magnetic systems able to drive nano “vehicles”, as well as magnetically labeled molecules, in human body fluids and tissues. Most available actuation systems can only attract magnetic elements in a relatively small workspace, limiting drug target applications to superficial tissues, and leaving no alternative cases where deep targeting is necessary. In this paper, we propose an electromagnetic actuation system able to push and deflect magnetic particles at distance of ~10 cm, enabling the manipulation of magnetic nano- and microparticles, as well as administration of drugs in tissues, which are not eligible for localized drug targeting with state-of-the-art systems. Laboratory experiments and modeling were conducted to prove the effectiveness of the proposed system. By further implementing our device, areas of the human body that previously were impossible to treat with magnetically labeled materials such as drugs, cells, and small molecules can now be accessible using the described system.

Computational simulation of electromagnetic fields on human targets for magnetic targeting applications

In the last few years, the use of nanoparticles for therapeutic applications has attracted the interest of many scientists, who are looking for effective methods to target nanoparticles linked to drugs directly to the diseased organs. Among them, magnetic targeting consists of magnetic systems (magnets or coils) which can impress high gradient magnetic fields and then magnetic forces on the magnetic nanoparticles. Despite some studies have reported an effective improvement in drug delivery by using this technique, there is still a paucity of studies able to quantify and explain the experimental results. In this scenario, "in silico" models allow to analyze and compare different magnetic targeting systems in their ability to generate the required magnetic field gradient for specific human targets.In this paper we then evaluated, by means of computational electromagnetics techniques, the attitude of various ad-hoc designed magnetic systems in targeting the heart tissues of differently aged human anatomical models.

A review of magnet systems for targeted drug delivery

Magnetic drug targeting is a method by which magnetic drug carriers in the body are manipulated by external magnetic fields to reach the target area. This method is potentially promising in applications for treatment of diseases like cancers, nervous system diseases, sudden sensorineural hearing loss, and so on, due to the advantages in that it can improve efficacy, reduce drug dosage and side effects. Therefore, it has received extensive attention in recent years. Successful magnetic drug targeting requires a good magnet system to guide the drug carriers to the target site. Up to date there have been many efforts to design the magnet systems for targeted drug delivery. However, there are few comprehensive reviews on these systems. Here we review the progresses made in this field. We summarized the systems already developed or proposed, and categorized them into two groups: static field magnet systems and varying field magnet systems. Based on the requirements for more powerful targeting performance, the prospects and the future research directions in this field are anticipated.

Magnetically assisted intraperitoneal drug delivery for cancer chemotherapy

Intraperitoneal (IP) chemotherapy has revived hopes during the past few years for the management of peritoneal disseminations of digestive and gynecological cancers. Nevertheless, a poor drug penetration is one key drawback of IP chemotherapy since peritoneal neoplasms are notoriously resistant to drug penetration. Recent preclinical studies have focused on targeting the aberrant tumor microenvironment to improve intratumoral drug transport. However, tumor stroma targeting therapies have limited therapeutic windows and show variable outcomes across different cohort of patients. Therefore, the development of new strategies for improving the efficacy of IP chemotherapy is a certain need. In this work, we propose a new magnetically assisted strategy to elevate drug penetration into peritoneal tumor nodules and improve IP chemotherapy. A computational model was developed to assess the feasibility and predictability of the proposed active drug delivery method. The key tumor pathophysiology, including a spatially heterogeneous construct of leaky vasculature, nonfunctional lymphatics, and dense extracellular matrix (ECM), was reconstructed in silico. The transport of intraperitoneally injected magnetic nanoparticles (MNPs) inside tumors was simulated and compared with the transport of free cytotoxic agents. Our results on magnetically assisted delivery showed an order of magnitude increase in the final intratumoral concentration of drug-coated MNPs with respect to free cytotoxic agents. The intermediate MNPs with the radius range of 200-300 nm yield optimal magnetic drug targeting (MDT) performance in 5-10 mm tumors while the MDT performance remains essentially the same over a large particle radius range of 100-500 nm for a 1 mm radius small tumor. The success of MDT in larger tumors (5-10 mm in radius) was found to be markedly dependent on the choice of magnet strength and tumor-magnet distance while these two parameters were less of a concern in small tumors. We also validated in silico results against experimental results related to tumor interstitial hypertension, conventional IP chemoperfusion, and magnetically actuated movement of MNPs in excised tissue.

Nanomagnetic-mediated drug delivery for the treatment of dental disease

Maintaining the vitality of the dental pulp, the highly innervated and highly vascular, innermost layer of the tooth, is a critical goal of any dental procedure. Upon injury, targeting the pulp with specific therapies is challenging because it is encased in hard tissues. This project describes a method that can effectively deliver therapeutic agents to the pulp. This method relies on the use of nanoparticles that can be actively steered using magnetic forces to the pulp, traveling through naturally occurring channels in the dentin (the middle layer of the tooth). This method can reduce the inflammation of injured pulp and improve the penetration of dental adhesives into dentin. Such a delivery method would be less expensive, and both less painful and less traumatic than existing therapeutic options available for treatment of injured dental pulp. This technique would be simple and could be readily translated to clinical use.

Understanding the dynamics of superparamagnetic particles under the influence of high field gradient arrays

The aim of this study was to characterize the behaviour of superparamagnetic particles in magnetic drug targeting (MDT) schemes. A 3-dimensional mathematical model was developed, based on the analytical derivation of the trajectory of a magnetized particle suspended inside a fluid channel carrying laminar flow and in the vicinity of an external source of magnetic force. Semi-analytical expressions to quantify the proportion of captured particles, and their relative accumulation (concentration) as a function of distance along the wall of the channel were also derived. These were expressed in terms of a non-dimensional ratio of the relevant physical and physiological parameters corresponding to a given MDT protocol. The ability of the analytical model to assess magnetic targeting schemes was tested against numerical simulations of particle trajectories. The semi-analytical expressions were found to provide good first-order approximations for the performance of MDT systems in which the magnetic force is relatively constant over a large spatial range. The numerical model was then used to test the suitability of a range of different designs of permanent magnet assemblies for MDT. The results indicated that magnetic arrays that emit a strong magnetic force that varies rapidly over a confined spatial range are the most suitable for concentrating magnetic particles in a localized region. By comparison, commonly used magnet geometries such as button magnets and linear Halbach arrays result in distributions of accumulated particles that are less efficient for delivery. The trajectories predicted by the numerical model were verified experimentally by acoustically focusing magnetic microbeads flowing in a glass capillary channel, and optically tracking their path past a high field gradient Halbach array.

Superparamagnetic Iron Oxide Nanoparticles in Musculoskeletal Biology

The use of platelet-rich plasma and mesenchymal stem cells has garnered much attention in orthopedic medicine, focusing on the biological aspects of cell function. However, shortly after systemic delivery, or even a local injection, few of the transplanted stem cells or platelets remain at the target site. Improvement in delivery, and the ability to track and monitor injected cells, would greatly improve clinical translation. Nanoparticles can effectively and quickly label most cells in vitro, and evidence to date suggests such labeling does not compromise the proliferation or differentiation of cells. A specific type of nanoparticle, the superparamagnetic iron oxide nanoparticle (SPION), is already employed as a magnetic resonance imaging (MRI) contrast agent. SPIONs can be coupled with cells or bioactive molecules (antibodies, proteins, drugs, etc.) to form an injectable complex for in vivo use. The biocompatibility, magnetic properties, small size, and custom-made surface coatings also enable SPIONs to be used for delivering and monitoring of small molecules, drugs, and cells, specifically to muscle, bone, or cartilage. Because SPIONs consist of cores made of iron oxides, targeting of SPIONs to a specific muscle, bone, or joint in the body can be enhanced with the help of applied gradient magnetic fields. Moreover, MRI has a high sensitivity to SPIONs and can be used for noninvasive determination of successful delivery and monitoring distribution in vivo. Gaps remain in understanding how the physical and chemical properties of nanomaterials affect biological systems. Nonetheless, SPIONs hold great promise for regenerative medicine, and progress is being made rapidly toward clinical applications in orthopedic medicine.

Remote magnetic targeting of iron oxide nanoparticles for cardiovascular diagnosis and therapeutic drug delivery: where are we now?

Magnetic resonance imaging (MRI) allows for an accurate assessment of both functional and structural cardiac parameters, and thereby appropriate diagnosis and validation of cardiovascular diseases. The diagnostic yield of cardiovascular MRI examinations is often increased by the use of contrast agents that are almost exclusively based on gadolinium compounds. Another clinically approved contrast medium is composed of superparamagnetic iron oxide nanoparticles (IONs). These particles may expand the field of contrast-enhanced cardiovascular MRI as recently shown in clinical studies focusing on acute myocardial infarction (AMI) and atherosclerosis. Furthermore, IONs open up new research opportunities such as remote magnetic drug targeting (MDT). The approach of MDT relies on the coupling of bioactive molecules and magnetic nanoparticles to form an injectable complex. This complex, in turn, can be attracted to and retained at a desired target inside the body with the help of applied magnetic fields. In comparison to common systemic drug applications, MDT techniques promise both higher concentrations at the target site and lower concentrations elsewhere in the body. Moreover, concurrent or subsequent MRI can be used for noninvasive monitoring of drug distribution and successful delivery to the desired organ in vivo. This review does not only illustrate the basic conceptual and biophysical principles of IONs, but also focuses on new research activities and achievements in the cardiovascular field, mainly in the management of AMI. Based on the presentation of successful MDT applications in preclinical models of AMI, novel approaches and the translational potential of MDT are discussed.

Polymer-iron oxide composite nanoparticles for EPR-independent drug delivery

Nanoparticle (NP)-based approaches to cancer drug delivery are challenged by the heterogeneity of the enhanced permeability and retention (EPR) effect in tumors and the premature attrition of payload from drug carriers during circulation. Here we show that such challenges can be overcome by a magnetophoretic approach to accelerate NP delivery to tumors. Payload-bearing poly(lactic-co-glycolic acid) NPs were converted into polymer-iron-oxide nanocomposites (PINCs) by attaching colloidal Fe3O4 onto the surface, via a simple surface modification method using dopamine polymerization. PINCs formed stable dispersions in serum-supplemented medium and responded quickly to magnetic field gradients above 1 kG/cm. Under the field gradients, PINCs were rapidly transported across physical barriers and into cells and captured under flow conditions similar to those encountered in postcapillary venules, increasing the local concentration by nearly three orders of magnitude. In vivo magnetophoretic delivery enabled PINCs to accumulate in poorly vascularized subcutaneous SKOV3 xenografts that did not support the EPR effect. In vivo magnetic resonance imaging, ex vivo fluorescence imaging, and tissue histology all confirmed that the uptake of PINCs was higher in tumors exposed to magnetic field gradients, relative to negative controls.

Halbach arrays consisting of cubic elements optimised for high field gradients in magnetic drug targeting applications

A key challenge in the development of magnetic drug targeting (MDT) as a clinically relevant technique is designing systems that can apply sufficient magnetic force to actuate magnetic drug carriers at useful tissue depths. In this study an optimisation routine was developed to generate designs of Halbach arrays consisting of multiple layers of high grade, cubic, permanent magnet elements, configured to deliver the maximum pull or push force at a position of interest between 5 and 50 mm from the array, resulting in arrays capable of delivering useful magnetic forces to depths past 20 mm. The optimisation routine utilises a numerical model of the magnetic field and force generated by an arbitrary configuration of magnetic elements. Simulated field and force profiles of optimised arrays were evaluated, also taking into account the forces required for assembling the array in practice. The resultant selection for the array, consisting of two layers, was then constructed and characterised to verify the simulations. Finally the array was utilised in a set of in vitro experiments to demonstrate its capacity to separate and retain microbubbles loaded with magnetic nanoparticles against a constant flow. The optimised designs are presented as light-weight, inexpensive options for applying high-gradient, external magnetic fields in MDT applications.

Cell-Based Therapy in TBI: Magnetic Retention of Neural Stem Cells In Vivo

Stem cell therapy is under active investigation for traumatic brain injury (TBI). Noninvasive stem cell delivery is the preferred method, but retention of stem cells at the site of injury in TBI has proven challenging and impacts effectiveness. To investigate the effects of applying a magnetic field on cell homing and retention, we delivered human neuroprogenitor cells (hNPCs) labeled with a superparamagnetic nanoparticle into post-TBI animals in the presence of a static magnetic field. We have previously devised a method of loading hNPCs with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles Molday ION Rhodamine B (MIRB™). Labeling of hNPCs (MIRB-hNPCs) does not affect hNPC viability, proliferation, or differentiation. The 0.6 tesla (T) permanent magnet was placed ∼4 mm above the injured parietal cortex prior to intracarotid injection of 4 × 10(4) MIRB-hNPCs. Fluorescence imaging, Perls' Prussian blue histochemistry, immunocytochemistry with SC121, a human-specific antibody, and T2-weighted magnetic resonance imaging ex vivo revealed there was increased homing and retention of MIRB-hNPCs in the injured cortex as compared to the control group in which MIRB-hNPCs were injected in the absence of a static magnetic field. Fluoro-Jade C staining and immunolabeling with specific markers confirmed the viability status of MIRB-hNPCs posttransplantation. These results show that increased homing and retention of MIRB-hNPCs post-TBI by applying a static magnetic field is a promising technique to deliver cells into the CNS for treatment of neurological injuries and neurodegenerative diseases.

Magnetically driven medical devices: a review

A widely accepted definition of a medical device is an instrument or apparatus that is used to diagnose, prevent or treat disease. Medical devices take a broad range of forms and utilize various methods to operate, such as physical, mechanical or thermal. Of particular interest in this paper are the medical devices that utilize magnetic field sources to operate. The exploitation of magnetic fields to operate or drive medical devices has become increasingly popular due to interesting characteristics of magnetic fields that are not offered by other phenomena, such as mechanical contact, hydrodynamics and thermodynamics. Today, there is a wide range of magnetically driven medical devices purposed for different anatomical regions of the body. A review of these devices is presented and organized into two groups: permanent magnetically driven devices and electromagnetically driven devices. Within each category, the discussion will be further segregated into anatomical regions (e.g., gastrointestinal, ocular, abdominal, thoracic, etc.).

Site-specific targeting of platelet-rich plasma via superparamagnetic nanoparticles

Background:

Muscle strains are one of the most common injuries treated by physicians. Standard conservative therapy for acute muscle strains usually involves short-term rest, ice, and nonsteroidal anti-inflammatory medications, but there is no clear consensus regarding treatments to accelerate recovery. Recently, clinical use of platelet-rich plasma (PRP) has gained momentum as an option for therapy and is appealing for many reasons, most notably because it provides growth factors in physiological proportions and it is autologous, safe, easily accessible, and potentially beneficial. Local delivery of PRP to injured muscles can hasten recovery of function. However, specific targeting of PRP to sites of tissue damage in vivo is a major challenge that can limit its efficacy.

Hypothesis:

Location of PRP delivery can be monitored and controlled in vivo with noninvasive tools.

Study Design:

Controlled laboratory study.

Methods:

Superparamagnetic iron oxide nanoparticles (SPIONs) can be visualized by both magnetic resonance imaging (MRI) (in vivo) and fluorescence microscopy (after tissue harvesting). PRP was labeled with SPIONs and administered by intramuscular injections of SPION-containing platelets. MRI was used to monitor the ability to manipulate and retain the location of PRP in vivo by placement of an external magnet. Platelets were isolated from whole blood and incubated with SPIONs. Following SPION incubation with PRP, a magnetic field was used to manipulate platelet location in culture dishes. In vivo, the tibialis anterior (TA) muscles of anesthetized Sprague-Dawley rats were injected with SPION-containing platelets, and MRI was used to track platelet position with and without a magnet worn over the TA muscles for 4 days.

Results:

The method used to isolate PRP yielded a high concentration (almost 4-fold increase) of platelets. In vitro experiments showed that the platelets successfully took up SPIONs and then rapidly responded to an applied magnetic field. Platelets without SPIONs did not respond to the magnetic field. In vivo experiments showed that the SPION-containing platelets can be noninvasively maintained at a specific site with the application of a magnetic field.

Conclusion:

PRP may be a useful product in the clinical treatment of muscle injuries, but one problem with using it as a therapeutic tool is retaining PRP at the site of injury. This study proposes a potential solution, with findings that support this method at the cell, whole muscle, and in vivo levels. Controlling the location of PRP will allow the clustering of PRP to enrich the target area with growth factors and will prevent loss of platelets over time at the site of injury.

Open challenges in magnetic drug targeting

The principle of magnetic drug targeting, wherein therapy is attached to magnetically responsive carriers and magnetic fields are used to direct that therapy to disease locations, has been around for nearly two decades. Yet our ability to safely and effectively direct therapy to where it needs to go, for instance to deep tissue targets, remains limited. To date, magnetic targeting methods have not yet passed regulatory approval or reached clinical use. Below we outline key challenges to magnetic targeting, which include designing and selecting magnetic carriers for specific clinical indications, safely and effectively reaching targets behind tissue and anatomical barriers, real-time carrier imaging, and magnet design and control for deep and precise targeting. Addressing these challenges will require interactions across disciplines. Nanofabricators and chemists should work with biologists, mathematicians, and engineers to better understand how carriers move through live tissues and how to optimize carrier and magnet designs to better direct therapy to disease targets. Clinicians should be involved early on and throughout the whole process to ensure the methods that are being developed meet a compelling clinical need and will be practical in a clinical setting. Our hope is that highlighting these challenges will help researchers translate magnetic drug targeting from a novel concept to a clinically available treatment that can put therapy where it needs to go in human patients.

Update on otitis media - prevention and treatment

Acute otitis media and otitis media with effusion are common childhood disorders, a source of significant morbidity, and a leading cause of antibiotic prescription in primary health care. Although effective treatments are available, some shortcomings remain, and thus better treatments would be welcome. Recent discoveries within the field of otitis media research relating to its etiology and pathogenesis have led to further investigation aimed at developing novel treatments. This article provides a review of the latest evidence relating to the understanding of acute otitis media and otitis media with effusion, current treatment strategies, their limitations, new areas of research, and novel strategies for treatment.

A dynamic magnetic shift method to increase nanoparticle concentration in cancer metastases: a feasibility study using simulations on autopsy specimens

A nanoparticle delivery system termed dynamic magnetic shift (DMS) has the potential to more effectively treat metastatic cancer by equilibrating therapeutic magnetic nanoparticles throughout tumors. To evaluate the feasibility of DMS, histological liver sections from autopsy cases of women who died from breast neoplasms were studied to measure vessel number, size, and spatial distribution in both metastatic tumors and normal tissue. Consistent with prior studies, normal tissue had a higher vascular density with a vessel-to-nuclei ratio of 0.48 ± 0.14 (n = 1000), whereas tumor tissue had a ratio of 0.13 ± 0.07 (n = 1000). For tumors, distances from cells to their nearest blood vessel were larger (average 43.8 μm, maximum 287 μm, n ≈ 5500) than normal cells (average 5.3 μm, maximum 67.8 μm, n ≈ 5500), implying that systemically delivered nanoparticles diffusing from vessels into surrounding tissue would preferentially dose healthy instead of cancerous cells. Numerical simulations of magnetically driven particle transport based on the autopsy data indicate that DMS would correct the problem by increasing nanoparticle levels in hypovascular regions of metastases to that of normal tissue, elevating the time-averaged concentration delivered to the tumor for magnetic actuation versus diffusion alone by 1.86-fold, and increasing the maximum concentration over time by 1.89-fold. Thus, DMS may prove useful in facilitating therapeutic nanoparticles to reach poorly vascularized regions of metastatic tumors that are not accessed by diffusion alone.