Computational simulations of magnetic particle capture in arterial flows

Enhancing capture efficiency of drug-carrier particles in the carotid sinus by utilizing a combination of magnetic fields: A numerical approach

Magnetic drug targeting is a relatively new method to treat vascular occlusion in different body parts. However, the effectiveness of this method can be affected due to the severity and location of the occlusion. This can lead to the injection of high dosages of drugs, which can cause serious side effects due to the deposition of drugs in unwanted parts. To mitigate these effects, this study investigates the potential of a guiding magnetic field in enhancing drug absorption for vascular occlusion treatment. The method relies on guiding magnetic nanoparticles (NPs) loaded with drugs toward the occlusion site using two external magnetic fields. Blood flow was modeled as non-Newtonian, considering shear-rate-dependent viscosity and unsteady at the inlet. To test this idea, a computational fluid dynamic (CFD) coupled with a discrete phase model (DPM) approach has been employed to simulate drug delivery in three-vessel structures with varying degrees of occlusion (45 %, 60 %, and 90 %). To avoid the escape of drug carriers, a secondary magnetic field was applied at the bifurcation point to direct the NPs to the site of blockage where the primary magnetic field acts. Then, the states with or without a guiding source at the bifurcation site are compared based on the capture efficiency of each structure. The simulation demonstrated a significant increase in NP capture at the target site, ranging from 2 % to 15 %, depending on the NP size. However, the severity of occlusion substantially impacted the secondary magnetic field's effectiveness. In the 90 % occlusion scenario, the method's efficiency decreased significantly from 26 % to 16 % for NP sizes exceeding 1.5μm. This study highlights the potential of guiding magnetic fields in improving drug delivery to target sites in vascular occlusion.

Nanoparticles as Drug Delivery Systems for the Targeted Treatment of Atherosclerosis

Atherosclerosis continues to be a leading cause of morbidity and mortality globally. The precise evaluation of the extent of an atherosclerotic plaque is essential for forecasting its likelihood of causing health concerns and tracking treatment outcomes. When compared to conventional methods used, nanoparticles offer clear benefits and excellent development opportunities for the detection and characterisation of susceptible atherosclerotic plaques. In this review, we analyse the recent advancements of nanoparticles as theranostics in the management of atherosclerosis, with an emphasis on applications in drug delivery. Furthermore, the main issues that must be resolved in order to advance clinical utility and future developments of NP research are discussed. It is anticipated that medical NPs will develop into complex and advanced next-generation nanobotics that can carry out a variety of functions in the bloodstream.

Development of high-efficiency superparamagnetic drug delivery system with MPI imaging capability

In this study, a high-efficiency superparamagnetic drug delivery system was developed for preclinical treatment of bladder cancer in small animals. Two types of nanoparticles with magnetic particle imaging (MPI) capability, i.e., single- and multi-core superparamagnetic iron oxide nanoparticles (SPIONs), were selected and coupled with bladder anti-tumor drugs by a covalent coupling scheme. Owing to the minimal particle size, magnetic field strengths of 270 mT with a gradient of 3.2 T/m and 260 mT with a gradient of 3.7 T/m were found to be necessary to reach an average velocity of 2 mm/s for single- and multi-core SPIONs, respectively. To achieve this, a method of constructing an in vitro magnetic field for drug delivery was developed based on hollow multi-coils arranged coaxially in close rows, and magnetic field simulation was used to study the laws of the influence of the coil structure and parameters on the magnetic field. Using this method, a magnetic drug delivery system of single-core SPIONs was developed for rabbit bladder therapy. The delivery system consisted of three coaxially and equidistantly arranged coils with an inner diameter of Φ50 mm, radial height of 85 mm, and width of 15 mm that were positioned in close proximity to each other. CCK8 experimental results showed that the three types of drug-coupled SPION killed tumor cells effectively. By adjusting the axial and radial positions of the rabbit bladder within the inner hole of the delivery coil structure, the magnetic drugs injected could undergo two-dimensional delivery motions and were delivered and aggregated to the specified target location within 12 s, with an aggregation range of about 5 mm × 5 mm. In addition, the SPION distribution before and after delivery was imaged using a home-made open-bore MPI system that could realistically reflect the physical state. This study contributes to the development of local, rapid, and precise drug delivery and the visualization of this process during cancer therapy, and further research on MPI/delivery synchronization technology is planned for the future.

An in silico model of the capturing of magnetic nanoparticles in tumour spheroids in the presence of flow

One of the main challenges in improving the efficacy of conventional chemotherapeutic drugs is that they do not reach the cancer cells at sufficiently high doses while at the same time affecting healthy tissue and causing significant side effects and suffering in cancer patients. To overcome this deficiency, magnetic nanoparticles as transporter systems have emerged as a promising approach to achieve more specific tumour targeting. Drug-loaded magnetic nanoparticles can be directed to the target tissue by applying an external magnetic field. However, the magnetic forces exerted on the nanoparticles fall off rapidly with distance, making the tumour targeting challenging, even more so in the presence of flowing blood or interstitial fluid. We therefore present a computational model of the capturing of magnetic nanoparticles in a test setup: our model includes the flow around the tumour, the magnetic forces that guide the nanoparticles, and the transport within the tumour. We show how a model for the transport of magnetic nanoparticles in an external magnetic field can be integrated with a multiphase tumour model based on the theory of porous media. Our approach based on the underlying physical mechanisms can provide crucial insights into mechanisms that cannot be studied conclusively in experimental research alone. Such a computational model enables an efficient and systematic exploration of the nanoparticle design space, first in a controlled test setup and then in more complex in vivo scenarios. As an effective tool for minimising costly trial-and-error design methods, it expedites translation into clinical practice to improve therapeutic outcomes and limit adverse effects for cancer patients.

Computational Assessment of Unsteady Flow Effects on Magnetic Nanoparticle Targeting Efficiency in a Magnetic Stented Carotid Bifurcation Artery

PURPOSE

Worldwide, cardiovascular disease is the leading cause of hospitalization and death. Recently, the use of magnetizable nanoparticles for medical drug delivery has received much attention for potential treatment of both cancer and cardiovascular disease. However, proper understanding of the interacting magnetic field forces and the hydrodynamics of blood flow is needed for effective implementation. This paper presents the computational results of simulated implant assisted medical drug targeting (IA-MDT) via induced magnetism intended for administering patient specific doses of therapeutic agents to specific sites in the cardiovascular system. The drug delivery scheme presented in this paper functions via placement of a faintly magnetizable stent at a diseased location in the carotid artery, followed by delivery of magnetically susceptible drug carriers guided by the local magnetic field. Using this method, the magnetic stent can apply high localized magnetic field gradients within the diseased artery, while only exposing the neighboring tissues, arteries, and organs to a modest magnetic field. The localized field gradients also produce the forces needed to attract and hold drug-containing magnetic nanoparticles at the implant site for delivering therapeutic agents to treat in-stent restenosis.

METHODS

The multi-physics computational model used in this work is from our previous work and has been slightly modified for the case scenario presented in this paper. The computational model is used to analyze pulsatile blood flow, particle motion, and particle capture efficiency in a magnetic stented region using the magnetic properties of magnetite (Fe3O4) and equations describing the magnetic forces acting on particles produced by an external cylindrical electromagnetic coil. The electromagnetic coil produces a uniform magnetic field in the computational arterial flow model domain, while both the particles and the implanted stent are paramagnetic. A Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of particles under the influence of a range of magnetic field strengths (Br = 2T, 4T, 6T, and 8T). Particle diameter sizes of 10 nm-4 µm in diameter were evaluated. Two dimensionless numbers were evaluated in this work to characterize relative effects of Brownian motion (BM), magnetic force induced particle motion, and convective blood flow on particle motion.

RESULTS

The computational simulations demonstrate that the greatest particle capture efficiency results for particle diameters within the micron range of 0.7-4 µm, specifically in regions where flow separation and vortices are at a minimum. Similar to our previous work (which did not involve the use of a magnetic stent), it was also observed that the capture efficiency of particles decreases substantially with particle diameter, especially in the superparamagnetic regime. Contrary to our previous work, using a magnetic stent tripled the capture efficiency of superparamagnetic particles. The highest capture efficiency observed for superparamagnetic particles was 78% with an 8 T magnetic field strength and 65% with a 2 T magnetic field strength when analyzing 100 nm particles. For 10 nm particles and an 8 T magnetic field strength, the particle capture efficiency was 55% and for a 2 T magnetic field strength the particle capture efficiency was observed to be 43%. Furthermore, it was found that larger magnetic field strengths, large particle diameter sizes (1 µm and above), and slower blood flow velocity improves the particle capture efficiency. The distribution of captured particles on the vessel wall along the axial and azimuthal directions is also discussed. Results for captured particles on the vessel wall along the axial flow direction showed that the particle density decreased along the axial direction, especially after the stented region. For the entrance section of the stented region, the captured particle density distribution along the axial direction is large, corresponding to the center-symmetrical distribution of the magnetic force in that section.

CONCLUSION

The simulation results presented in this work have shown to yield favorable capture efficiencies for micron range particles and superparamagnetic particles using magnetized implants such as the stent discussed in this work. The results presented in this work justify further investigation of MDT as a treatment technique for cardiovascular disease.

Targeting Magnetic Nanoparticles in Physiologically Mimicking Tissue Microenvironment

Magnetic nanoparticles as drug carriers, despite showing immense promises in preclinical trials, have remained to be only of limited use in real therapeutic practice primarily due to unresolved anomalies concerning their grossly contrasting controllability and variability in performance in artificial test benches as compared to human tissues. To circumvent the deficits of reported in vitro drug testing platforms that deviate significantly from the physiological features of the living systems and result in this puzzling contrast, here, we fabricate a biomimetic microvasculature in a flexible tissue phantom and demonstrate distinctive mechanisms of magnetic-field-assisted controllable penetration of biocompatible iron oxide nanoparticles across the same, exclusively modulated by tissue deformability, which has by far remained unraveled. Our experiments deciphering the transport of magnetic nanoparticles in a blood analogue medium unveil a decisive interplay of the flexibility of the microvascular pathways, magnetic pull, and viscous friction toward orchestrating the optimal vascular penetration and targeting efficacy of the nanoparticles in colorectal tissue-mimicking bioengineered media. Subsequent studies with biological cells confirm the viability of using localized magnetic forces for aiding nanoparticle penetration within cancerous lesions. We establish nontrivially favorable conditions to induce a threshold force for vascular rupture and eventual target of the nanoparticles toward the desired extracellular site. These findings appear to be critical in converging the success of in vitro trials toward patient-specific targeted therapies depending on personalized vascular properties obtained from medical imaging data.

Euler-Lagrange numerical simulation of improved magnetic drug delivery in a three-dimensional CT-based carotid artery bifurcation

BACKGROUND AND OBJECTIVE

Magnetic drug targeting (MDT) is a promising method to improve the therapy efficiency for cardiovascular diseases (CVDs) and cancers. In MDT, therapeutic agents are bonded to superparamagnetic iron oxide nanoparticle (SPION) cores and then are guided toward the damaged tissue through a magnetic field. Fundamentally, it's vital to steer the SPIONs to the desired location to increase the capture efficiency at the target lesion. Hence, the present study aims to enhance the drug delivery to the desired branch in a carotid bifurcation. Besides, it is tried to decrement the particles' entry to the unwanted outlet by using four different magnet configurations (with a maximum magnetic flux density of 0.4 T) implanted adjacent to the artery wall. Also, the effect of particles' diameter -ranging from 200 nm to 2 µm- on the drug delivery performance is studied in the four cases.

METHODS

The Eulerian-Lagrangian approach with one-way coupling is employed for numerical simulation of the problem using the finite element method (FEM). The dominant forces acting on particles are drag and magnetophoretic. A computed tomography (CT) model of the carotid bifurcation is adopted to have a 3D realistic geometry. The blood flow is considered to be laminar, incompressible, pulsatile, and non-Newtonian. Boundary conditions are applied using the three-element Windkessel equation.

RESULTS

Results are presented in terms of velocity, pressure, magnetic field flux density, wall shear stress, and streamlines. Also, the number of particles in each direction is presented for the four studied cases. The results show that using proper magnets configurations makes it possible to guide more particles to the desired branch (up to 4%) while preventing particles from entering the unwanted branch (up to 13%). By defining connectivity between oscillatory shear index (OSI) value and magnetic drug delivery efficacy, it becomes clear that places with lower OSI values are more proper to place the magnets than areas with higher OSI values.

CONCLUSIONS

It was observed that increasing the diameter of particles does not necessarily result in a higher drug delivery efficiency. The configuration of the magnets and the size of particles are the main affecting parameters that should be chosen precisely to meet the most efficient drug delivery performance. Magnetic drug targeting (MDT) is a promising method to improve the therapy efficiency for cardiovascular diseases (CVDs) and cancers. Fundamentally, it's vital to steer the superparamagnetic iron oxide nanoparticles (SPIONs) to the target lesion location to increase the capture efficiency. Hence, the present study aims to enhance the drug delivery to the desired branch in a 3D carotid bifurcation. Besides, it is tried to decrement the particles' entry to the unwanted outlet by using four different magnet configurations implanted adjacent to the artery wall. The Eulerian-Lagrangian approach with one-way coupling is employed for numerical simulation of the problem using the finite element method (FEM). The dominant forces acting on particles are drag and magnetophoretic. The blood flow is laminar, incompressible, pulsatile, and non-Newtonian. The results show that it is possible to guide more particles to the desired branch (up to 4%) while preventing particles from entering the unwanted branch (up to 13%). By defining connectivity between oscillatory shear index (OSI) value and magnetic drug delivery efficacy, it becomes clear that places with lower OSI values are more proper to place the magnets than areas with higher OSI values.

Numerical study of drug delivery through the 3D modeling of aortic arch in presence of a magnetic field

Magnetic drug delivery known as smart technique in medicine is basically according to combining the drug inside capsules with the magnetic property or attaching the drug with magnetic surfaces at the micro- and nanoscale. In the present study, magnetic drug delivery in the aortic artery has been investigated. To approach the more realistic problem conditions of blood flow rheology, the effect of parameters such as non-Newtonian viscosity and oscillating input has been put into consideration. Also, the investigated geometrical parameters of arteries of the aortic arch have been chosen similar to the real size. The results indicate that an increase in the diameter of microparticles rises the efficiency of particles absorption. In addition, the influence of changing the direction of the wire carrying electricity and thus changing the direction of magnetic field on magnetic drug delivery has been examined in the geometry of the aortic arc and it is found that the highest particle absorption efficiency takes place in the case that the wire is parallel to the direction of y-axis. As an example, the results show that the rate of absorption efficiency for particles with 3 µm dia is 26.83% and 19.39% when the wire generating magnetic field is parallel to the direction of y-axis and z-axis, respectively, and this value is 10.91% for the case without a magnetic field. The number of particles released from different part of the aortic arch also is affected by the direction of magnetic field. This value illustrates that the percentage of particles released from different states, is equal when the magnetic field is absent and the wire carrying electricity is parallel to y-axis and z-axis. However, the number of particles released from the 2 outputs of the left carotid and left subclavian is less than the other 2 states (i.e., the state when there is not a magnetic field, and the state when the electric current direction is parallel to the y-axis direction) for the state when the wire carrying current is parallel to the z-axis.

Numerical simulation of magnetic nano drug targeting to atherosclerosis: Effect of plaque morphology (stenosis degree and shoulder length)

BACKGROUND AND OBJECTIVE

Nanoparticle-mediated targeted drug delivery is a promising option for treatment of atherosclerosis. However, the drug targeting may be affected by multiple factors. Considerable attentions have been focused on the influences of external factors, e.g., magnetic field, drug-loaded particle, but internal factors, e.g., plaque morphology (stenosis degree and shoulder length), have not received any attention yet. Therefore, we investigate the impact of plaque morphology on magnetic nanoparticles targeting under the action of an external field.

METHOD

Numerical simulation, based on Eulerian-Lagrangian coupled Fluid-Solid Interaction, is performed in ANSYS Workbench platform. Blood flow is solved by Navier-Stokes equation, particles are tracked by discrete phase model, and the incorporated effect is obtained by two-way method. Plaques with varying stenosis degrees and shoulder lengths are acquired by manually modifying the geometry of patient-specific. The quantified variables include targeted delivery efficiency (deposition+adhesive strength) of particles and plaque injury characterized by temporal-spatial averaged shear stress (TAWSS¯) during the process of drug transport, in which the critical deposition velocity is determined by plaques and particles, the DEFINE_DPM_BC and User Defined Memory are employed to evaluate whether the particles are deposited, and to store the total number and the adhesive strength of particles deposited on the plaque.

RESULTS

Results signify that, with an increment of plaque stenosis degree, the deposition of particle and the adhesive strength between particle and plaque decrease, while the TAWSS¯ increases. Furthermore, for the same stenosis degree, with the increase of plaque shoulder length, the deposition and the adhesive strength of particle increase, and the TAWSS¯ decreases.

CONCLUSIONS

Results demonstrates that the plaque with smaller stenosis degree or longer shoulder length may achieve a better treatment effect in view of the higher targeted delivery efficiency of particles and the lighter shear damage to plaque itself during the process of drug transport.

Model of Magnetic Particle Capture Under Physiological Flow Rates for Cytokine Removal During Cardiopulmonary Bypass

OBJECTIVE

The objective of this study is to design a physical model of a magnetic filtration system which can separate magnetic nanoparticle (MNP)-tagged cytokines from fluid at physiologically relevant flow rates employed during cardiopulmonary bypass (CPB) procedures.

METHODS

The Navier-Stokes equations for the pressure driven flow in the chamber and the quasistatic stray magnetic field produced by an array of permanent magnets were solved using finite element analysis in COMSOL Multiphysics for 2D and 3D representations of the flow chamber. Parameters affecting the drag and magnetic forces including flow chamber dimensions, high gradient magnet array configurations, and particle properties, were changed and evaluated for their effect on MNP capture.

RESULTS

Flow chamber dimensions which achieve appropriate flow conditions for CPB were identified, and magnetic force within the chamber decreased with increased chamber height. A magnetic "block" array produced the highest magnetic force within the chamber. Polymeric microparticles loaded with MNPs were shown to have increased particle capture with increased hydrodynamic diameter.

CONCLUSION

The model achieved a predicted efficiency up to 100% capture in a single-pass of fluid flowing at 1.75 L/min.

SIGNIFICANCE

This work is an important step in designing a magnetic flow chamber that can remove the magnetically tagged cytokines under high flow employed during CPB. Cytokines have been shown to stimulate the systemic inflammatory response (SIR) associated with CPB and are an established therapeutic target to mitigate the SIR. In the long term, this work aims to guide researchers in the more accurate design of magnetic separation systems.

Biodistribution, biocompatibility and targeted accumulation of magnetic nanoporous silica nanoparticles as drug carrier in orthopedics

BACKGROUND

In orthopedics, the treatment of implant-associated infections represents a high challenge. Especially, potent antibacterial effects at implant surfaces can only be achieved by the use of high doses of antibiotics, and still often fail. Drug-loaded magnetic nanoparticles are very promising for local selective therapy, enabling lower systemic antibiotic doses and reducing adverse side effects. The idea of the following study was the local accumulation of such nanoparticles by an externally applied magnetic field combined with a magnetizable implant. The examination of the biodistribution of the nanoparticles, their effective accumulation at the implant and possible adverse side effects were the focus. In a BALB/c mouse model (n = 50) ferritic steel 1.4521 and Ti90Al6V4 (control) implants were inserted subcutaneously at the hindlimbs. Afterwards, magnetic nanoporous silica nanoparticles (MNPSNPs), modified with rhodamine B isothiocyanate and polyethylene glycol-silane (PEG), were administered intravenously. Directly/1/7/21/42 day(s) after subsequent application of a magnetic field gradient produced by an electromagnet, the nanoparticle biodistribution was evaluated by smear samples, histology and multiphoton microscopy of organs. Additionally, a pathohistological examination was performed. Accumulation on and around implants was evaluated by droplet samples and histology.

RESULTS

Clinical and histological examinations showed no MNPSNP-associated changes in mice at all investigated time points. Although PEGylated, MNPSNPs were mainly trapped in lung, liver, and spleen. Over time, they showed two distributional patterns: early significant drops in blood, lung, and kidney and slow decreases in liver and spleen. The accumulation of MNPSNPs on the magnetizable implant and in its area was very low with no significant differences towards the control.

CONCLUSION

Despite massive nanoparticle capture by the mononuclear phagocyte system, no significant pathomorphological alterations were found in affected organs. This shows good biocompatibility of MNPSNPs after intravenous administration. The organ uptake led to insufficient availability of MNPSNPs in the implant region. For that reason, among others, the nanoparticles did not achieve targeted accumulation in the desired way, manifesting future research need. However, with different conditions and dimensions in humans and further modifications of the nanoparticles, this principle should enable reaching magnetizable implant surfaces at any time in any body region for a therapeutic reason.

Magnetic Accumulation of SPIONs under Arterial Flow Conditions: Effect of Serum and Red Blood Cells

Magnetic drug targeting utilizes an external magnetic field to target superparamagnetic iron oxide nanoparticles (SPIONs) and their cargo to the diseased vasculature regions. In the arteries, the flow conditions affect the behavior of magnetic particles and the efficacy of their accumulation. In order to estimate the magnetic capture of SPIONs in more physiological-like settings, we previously established an ex vivo model based on human umbilical cord arteries. The artery model was employed in our present studies in order to analyze the effects of the blood components on the efficacy of magnetic targeting, utilizing 2 types of SPIONs with different physicochemical characteristics. In the presence of freshly isolated human plasma or whole blood, a strong increase in iron content measured by AES was observed for both particle types along the artery wall, in parallel with clotting activation due to endogenous thrombin generation in plasma. Subsequent studies therefore utilized SPION suspensions in serum and washed red blood cells (RBCs) at hematocrit 50%. Interestingly, in contrast to cell culture medium suspensions, magnetic accumulation of circulating SPION-3 under the external magnet was achieved in the presence of RBCs. Taken together, our data shows that the presence of blood components affects, but does not prevent, the magnetic accumulation of circulating SPIONs.

Numerical simulation of magnetic drug targeting to a tumor in the simplified model of the human lung

BACKGROUND

Magnetic drug targeting improves effectiveness of medicine application and reduces its side effects. In this method, drugs with magnetic core are released in the lung and they are steered towards the tumor by applying an external magnetic field. A number of researchers utilized numerical methods to study particle deposition in the lung, but magnetic drug delivery to the tumors in the human lung has not been addressed yet.

METHOD

In the present study, Weibel model is used for human airway geometry from generation G0-G3. Moreover, a tumor is considered in the lung, which is located in G2. Particles are made of iron oxide magnetic cores and poly lactic coglycolic acid shells. Fluid flow is assumed laminar and particles are coupled with the fluid by one-way method. The magnetic field is produced by a coil with law current intensities instead of a wire with high current intensities. Influences of various parameters such as particle diameter, magnetic source position, current intensity, and inlet mass flow rate and tumor size on the deposition efficiency on the tumor surface are reported.

RESULTS

Results show that magnetic drug targeting enhances deposition efficiency on the tumor surface Furthermore, when the current intensity rises from 10 (A) to 20 (A), tumor enlarging, and increasing particle diameter, lead to deposition efficiency enhancement, but efficiency decreases by increasing mass flow rate. However, when current intensity is 20 (A), deposition efficiency decreases in two situations. The first situation is when mass flow rate is 7 (L/min) and particle diameter is 9 (µm), and the second one is in 10 (L/min) mass flow rate and 9 (µm) diameter.

CONCLUSION

The results demonstrated that magnetic drug targeting is applicable and suitable for all tumors specially for small tumors (r/R = 0.5 in this case) that efficiency increase from 0% in the absence of magnetic field to more than 2% in the presence of magnetic field.

Magnetic drug targeting simulations in blood flows with fluid-structure interaction

We present fluid-structure interaction simulations of magnetic drug targeting (MDT) in blood flows. In this procedure, a drug is attached to ferromagnetic particles to externally direct it to a specific target after it is injected inside the body. The goal is to minimize the healthy tissue affected by the treatment and to maximize the number of particles that reach the target location. Magnetic drug targeting has been studied both experimentally and theoretically by several authors. In recent years, computational fluid dynamics simulations of MDT in blood flows have been conducted to obtain further insight on the combination of parameters that provide the best capture efficiency. However, to this day, no computational study addressed MDT in a fluid-structure interaction setting. With this paper, we aim to fill this gap and investigate the impact of the solid deformation on the capture efficiency.

Adsorption combined with superconducting high gradient magnetic separation technique used for removal of arsenic and antimony

Manganese iron oxide (MnFe₂O₄), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe₂O₄ adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL^-1, MnFe₂O₄ material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe₂O₄ was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin^-1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe₂O₄ solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R²=0.87-0.99).

Numerical simulations of targeted delivery of magnetic drug aerosols in the human upper and central respiratory system: a validation study

In the present study, we investigate the concept of the targeted delivery of pharmaceutical drug aerosols in an anatomically realistic geometry of the human upper and central respiratory system. The geometry considered extends from the mouth inlet to the eighth generation of the bronchial bifurcations and is identical to the phantom model used in the experimental studies of Banko et al. (2015 Exp. Fluids56, 1-12 (doi:10.1007/s00348-015-1966-y)). In our computer simulations, we combine the transitional Reynolds-averaged Navier-Stokes (RANS) and the wall-resolved large eddy simulation (LES) methods for the air phase with the Lagrangian approach for the particulate (aerosol) phase. We validated simulations against recently obtained magnetic resonance velocimetry measurements of Banko et al. (2015 Exp. Fluids56, 1-12. (doi:10.1007/s00348-015-1966-y)) that provide a full three-dimensional mean velocity field for steady inspiratory conditions. Both approaches produced good agreement with experiments, and the transitional RANS approach is selected for the multiphase simulations of aerosols transport, because of significantly lower computational costs. The local and total deposition efficiency are calculated for different classes of pharmaceutical particles (in the 0.1 μm≤d_p≤10 μm range) without and with a paramagnetic core (the shell-core particles). For the latter, an external magnetic field is imposed. The source of the imposed magnetic field was placed in the proximity of the first bronchial bifurcation. We demonstrated that both total and local depositions of aerosols at targeted locations can be significantly increased by an applied magnetization force. This finding confirms the possible potential for further advancement of the magnetic drug targeting technique for more efficient treatments for respiratory diseases.

Optimization of an endovascular magnetic filter for maximized capture of magnetic nanoparticles

To computationally optimize the design of an endovascular magnetic filtration device that binds iron oxide nanoparticles and to validate simulations with experimental results of prototype devices in physiologic flow testing. Three-dimensional computational models of different endovascular magnetic filter devices assessed magnetic particle capture. We simulated a series of cylindrical neodymium N52 magnets and capture of 1500 iron oxide nanoparticles infused in a simulated 14 mm-diameter vessel. Device parameters varied included: magnetization orientation (across the diameter, "D", along the length, "L", of the filter), magnet outer diameter (3, 4, 5 mm), magnet length (5, 10 mm), and spacing between magnets (1, 3 mm). Top designs were tested in vitro using ⁸⁹Zr-radiolabeled iron oxide nanoparticles and gamma counting both in continuous and multiple pass flow model. Computationally, "D" magnetized devices had greater capture than "L" magnetized devices. Increasing outer diameter of magnets increased particle capture as follows: "D" designs, 3 mm: 12.8-13.6 %, 4 mm: 16.6-17.6 %, 5 mm: 21.8-24.6 %; "L" designs, 3 mm: 5.6-10 %, 4 mm: 9.4-15.8 %, 5 mm: 14.8-21.2 %. In vitro, while there was significant capture by all device designs, with most capturing 87-93 % within the first two minutes, compared to control non-magnetic devices, there was no significant difference in particle capture with the parameters varied. The computational study predicts that endovascular magnetic filters demonstrate maximum particle capture with "D" magnetization. In vitro flow testing demonstrated no difference in capture with varied parameters. Clinically, "D" magnetized devices would be most practical, sized as large as possible without causing intravascular flow obstruction.

Magnetic nanoparticles and blood flow behavior in non-Newtonian pulsating flow within the carotid artery in drug delivery application

Nanoparticles play an important role in the molecular diagnosis, treatment, and monitoring therapeutic outcomes in various diseases. Magnetic nanoparticles are being of great interest due to their unique purposes, especially medicine, in which the application of magnetic nanoparticles is much promising. Magnetic nanoparticles have been actively investigated as the next generation of targeted drug delivery for more than three decades. This article is devoted to study on the magnetic drug targeting technique by particle tracking in the presence of a magnetic field in the carotid artery. The results showed that applying a magnetic field on the secondary branch of the external carotid artery in a pulsating non-Newtonian flow drove nanoparticles inside this sub-branch, while none of them entered that branch in the absence of magnetic field on the internal carotid artery. Wall shear stress distributions showed that high shear stress occurs near the bifurcation region, and its maximum value belongs to the junction of internal carotid artery and external carotid artery.

Augmenting regional and targeted delivery in the pulmonary acinus using magnetic particles

Background

It has been hypothesized that by coupling magnetic particles to inhaled therapeutics, the ability to target specific lung regions (eg, only acinar deposition), or even more so specific points in the lung (eg, tumor targeting), can be substantially improved. Although this method has been proven feasible in seminal in vivo studies, there is still a wide gap in our basic understanding of the transport phenomena of magnetic particles in the pulmonary acinar regions of the lungs, including particle dynamics and deposition characteristics.

Methods

Here, we present computational fluid dynamics-discrete element method simulations of magnetically loaded microdroplet carriers in an anatomically inspired, space-filling, multi-generation acinar airway tree. Breathing motion is modeled by kinematic sinusoidal displacements of the acinar walls, during which droplets are inhaled and exhaled. Particle dynamics are governed by viscous drag, gravity, and Brownian motion as well as the external magnetic force. In particular, we examined the roles of droplet diameter and volume fraction of magnetic material within the droplets under two different breathing maneuvers.

Results and discussion

Our results indicate that by using magnetic-loaded droplets, 100% of the particles that enter are deposited in the acinar region. This is consistent across all particle sizes investigated (ie, 0.5–3.0 µm). This is best achieved through a deep inhalation maneuver combined with a breath-hold. Particles are found to penetrate deep into the acinus and disperse well, while the required amount of magnetic material is maintained low (<2.5%). Although particles in the size range of ~90–500 nm typically show the lowest deposition fractions, our results suggest that this feature could be leveraged to augment targeted delivery.

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.

Capture Efficiency of Biocompatible Magnetic Nanoparticles in Arterial Flow: A Computer Simulation for Magnetic Drug Targeting

The primary limitation of magnetic drug targeting (MDT) relates to the strength of an external magnetic field which decreases with increasing distance. Small nanoparticles (NPs) displaying superparamagnetic behaviour are also required in order to reduce embolization in the blood vessel. The small NPs, however, make it difficult to vector NPs and keep them in the desired location. The aims of this work were to investigate parameters influencing the capture efficiency of the drug carriers in mimicked arterial flow. In this work, we computationally modelled and evaluated capture efficiency in MDT with COMSOL Multiphysics 4.4. The studied parameters were (i) magnetic nanoparticle size, (ii) three classes of magnetic cores (Fe3O4, Fe2O3, and Fe), and (iii) the thickness of biocompatible coating materials (Au, SiO2, and PEG). It was found that the capture efficiency of small particles decreased with decreasing size and was less than 5 % for magnetic particles in the superparamagnetic regime. The thickness of non-magnetic coating materials did not significantly influence the capture efficiency of MDT. It was difficult to capture small drug carriers (D<200 nm) in the arterial flow. We suggest that the MDT with high-capture efficiency can be obtained in small vessels and low-blood velocities such as micro-capillary vessels.

Magnetophoresis 'meets' viscoelasticity: deterministic separation of magnetic particles in a modular microfluidic device

The deflection of magnetic beads in a microfluidic channel through magnetophoresis can be improved if the particles are somehow focused along the same streamline in the device. We design and fabricate a microfluidic device made of two modules, each one performing a unit operation. A suspension of magnetic beads in a viscoelastic medium is fed to the first module, which is a straight rectangular-shaped channel. Here, the magnetic particles are focused by exploiting fluid viscoelasticity. Such a channel is one inlet of the second module, which is a H-shaped channel, where a buffer stream is injected in the second inlet. A permanent magnet is used to displace the magnetic beads from the original to the buffer stream. Experiments with a Newtonian suspending fluid, where no focusing occurs, are carried out for comparison. When viscoelastic focusing and magnetophoresis are combined, magnetic particles can be deterministically separated from the original streamflow to the buffer, thus leading to a high deflection efficiency (up to ~96%) in a wide range of flow rates. The effect of the focusing length on the deflection of particles is also investigated. Finally, the proposed modular device is tested to separate magnetic and non-magnetic beads.

On Computational Fluid Dynamics Study of Magnetic Drug Targeting

Magnetic drug targeting is continuing to draw attention as a potential technique for cancer and tumour treatment. This paper focuses on the development of computational fluid dynamic models for magnetic drug targeting. Magnetic particle capture has been simulated in a 90o coronary artery bend of circular tube for a range of different particle sizes. The magnetic field is produced by a current carrying wire. It has been found that increasing the sizes of magnetic particles increases the capture of particles. Extensions are made on the model to include the effects of non-Newtonian fluid and the pulsating nature of blood flow. These extensions improved the basic model by simulating a more physiologically accurate application of magnetic drug targeting. A reduction of the particle capture efficiency is experienced based on this physiologically accurate model. Time of injection over the flow cycle of the pulsating nature of blood flow greatly influences the particle capture efficiency.

Lagrangian Magnetic Particle Tracking Through Stenosed Artery Under Pulsatile Flow Condition

Drug delivery technologies are an important area within biomedicine. Targeted drug delivery aims to reduce the undesired side effects of drug usage by directing or capturing the active agents near a desired site within the body. This is particularly beneficial in, for instance, cancer chemotherapy, where the side effects of general (systemic) drug administration can be severe. Herein, a numerical investigation of unsteady magnetic drug targeting (MDT) using functionalized magnetic microspheres in partly occluded blood vessels is presented considering the effects of particle-fluid coupling on the transport and capture of the magnetic particles. An Eulerian–Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ansys fluent. An implantable cylindrical permanent magnet insert is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted and the influence of the flow Re, magnetic insert diameter, and its radial and axial position on the “targeting efficiency” is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug-carrying magnetic particles in a predesignated target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for in vitro set up for the investigation of MDT in stenosed blood vessels.

Magnetic Drug Targeting in Partly Occluded Blood Vessels Using Magnetic Microspheres

Magnetic drug targeting can be used for treating stenosis and thrombosis in partly occluded blood vessels. Herein, a numerical investigation of magnetic drug targeting using functionalized magnetic microspheres in partly occluded blood vessels is conducted. An Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow. An implantable cylindrical permanent magnet insert is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted, and the influence of the flow Re, magnetic insert diameter, and its radial and axial position on the “targeting efficiency” is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug-carrying magnetic particles in a predesignated target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for an in vitro setup for the investigation of magnetic drug targeting in stenosed blood vessels.