Least-Squares Finite Element Method for Solving Stokes Flow under Point Source Magnetic Field

The least-squares finite element method (LSFEM) is successfully employed for the discretization of the Stokes equations and the numerical computation of the behaviour of two-dimensional Stokes flow in a straight rectangular channel under the effect of a point-source magnetic field. LSFEM has several advantages in terms of theory and computing, where it can always create a symmetric, positive-definite algebraic system of equations. It also allows for using an equal order shape function for both velocity and pressure, and it is not required to satisfy the Ladyzhenskaya–Babuška–Brezzi (LBB) condition. Despite this, LSFEM has an issue where low-order nodal expansions tend to lock. Thus, the present study proposes the discretization of the problem domain using higher-order nodes elements with full numerical integration. Results concerning velocity contour and streamlines pattern are shown. On the basis of current findings, it can be concluded that the LSFEM can be used to solve Stokes flow problem under the point source 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.

Enhanced Targeted Drug Delivery Through Controlled Release in a Three-Dimensional Vascular Tree

“Controlled particle release and targeting” is a technique using particle release score map (PRSM) and transient particle release score map (TPRSM) via backtracking to determine optimal drug injection locations for achieving an enhanced target efficiency (TE). This paper investigates the possibility of targeting desired locations through an idealized but complex three-dimensional (3D) vascular tree geometry under realistic hemodynamic conditions by imposing a Poiseuille velocity profile and a Womersley velocity profile derived from cine phase contrast magnetic resonance imaging (MRI) data for steady and pulsatile simulations, respectively. The shear thinning non-Newtonian behavior of blood was accounted for by the Carreau–Yasuda model. One-way coupled Eulerian–Lagrangian particle tracking method was used to record individual drug particle trajectories. Particle size and density showed negligible influence on the particle fates. With the proposed optimal release scoring algorithm, multiple optimal release locations were determined under steady flow conditions, whereas there was one unique optimal release location under pulsatile flow conditions. The initial in silico results appear promising, showing on average 66% TE in the pulsatile simulations, warranting further studies to improve the mathematical model and experimental validation.

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.

Intrathecal magnetic drug targeting using gold-coated magnetite nanoparticles in a human spine model

AIM

We aimed to magnetically guide and locally confine nanoparticles in desired locations within the spinal canal to achieve effective drug administration for improved treatment of chronic pain, cancers, anesthesia and spasticity.

MATERIALS & METHODS

We developed a physiologically and anatomically consistent in vitro human spine model to test the feasibility of intrathecal magnetic drug targeting. Gold-coated magnetite nanoparticles were infused into the model and targeted to specific regions using external magnetic fields. Experiments and simulations aiming to determine the effect of key parameters, such as magnet strength, duration of magnetic field exposure, magnet location and ferrous implants, on the collection efficiency of superparamagnetic nanoparticles in targeted regions were performed.

RESULTS

An 891% increase in nanoparticle collection efficiency within the target region was achieved using intrathecal magnetic drug targeting when compared with the control. Nanoparticle collection efficiency at the target region increased with time and reached a steady value within 15 min. Ferrous epidural implants generated sufficiently high-gradient magnetic fields, even when magnets were placed at a distance equal to the space between a patient's epidermis and spinal canal.

CONCLUSION

Our experiments indicate that intrathecal magnetic drug targeting is a promising technique for concentrating and localizing drugs at targeted sites within the spinal canal for treating diseases affecting the CNS.