Influence of local particle concentration gradient forces on the flow-mediated mass transport in a numerical model of magnetic drug targeting

Magnetic nanoparticles have been widely applied in the nanomedicine field: therapies based on magnetic drug targeting have shown promising results towards the improvement of the current state of the art of medical treatments. Particles interaction with their carrying flow or the surrounding tissues still needs to be completely understood, as well as the mechanisms underlying interparticle interactions. These interactions can potentially promote particles aggregation in the fluid doman and therefore influence the therapy outcome. This study presents a numerical model to describe particles magnetohydrodynamics in a realistic setup for magnetic drug targeting. The focus is a quantitative analysis of the contribution of the local ferrofluid concentration gradients to the magnetic fluid volume force, as well as an investigation on the dependence of the magnetic fluid volume force on particles diameter and ferrofluid concentration. The results show that the main contribution to the magnetic fluid volume force is the magnetic field gradients term. However, the concentration gradients term ranges in the same order of magnitude and therefore cannot be neglected in the force formulation. In addition, the molar concentration distribution has been found to change with different force formulations and with different values of the molar influx too. The model outlines that the magnetic fluid volume force increases with the particle diameter and the ferrofluid concentration. However, both relationships are not linear, but more complex. The described approach proves to be versatile and further applicable to more complex geometries and scenarios. In addition, the outcome and the achievements of the presented numerical model provide for the first time insights into the role of the local ferrofluid concentration gradients in the determination of the magnetic fluid volume force and represent a starting point for further investigations of the mechanisms underlying the flow-mediated ferrofluid mass transport.