Study on Optimizing High-Gradient Magnetic Separation—Part 1: Improvement of Magnetic Particle Retention Based on CFD Simulations

Abstract

The introduction of functionalized magnetizable particles for the purification of enzymes or for the multi-use of pre-immobilized biocatalysts offers a great potential for time and cost savings in biotechnological process design. The selective separation of the magnetizable particles is performed for example by a high-gradient magnetic separator. In this study FEM and CFD simulations of the magnetic field and the fluid flow field within a filter chamber of a magnetic separator were carried out, to find an optimal separator design. The motion of virtual magnetizable particles was calculated with a one-way coupled Lagrangian approach in order to test many geometric and parametric variations in reduced time. It was found that a flow homogenisator smoothed the fluid flow, so that the linear velocity became nearly equal over the cross section in the direction of flow. Furthermore the retention of magnetizable particles increases with a high total edge length within the filter matrix.

Agglomeration behaviour of magnetic microparticles during separation and recycling processes in mRNA purification

“…If the magnetic particle‐based separation technique is to be carried out in a technical scale production of mRNA‐based vaccine, it is not possible by using the magnetic separators used in the laboratory scale. Magnetic separators suitable for this purpose based on the principle of high‐gradient magnetic separation (HGMS), which are operated in through‐flow (“magnetic filters”), have been and are being developed in particular by Franzreb [1, 2, 58, 59] and in own work [6–8, 57, 60]. The magnetic particle suspension to be processed — in this case oligo(dT) 25 ‐functionalized magnetic beads or mRNA‐loaded oligo(dT) 25 ‐functionalized magnetic beads — is then placed in a feed vessel, which is stirred to avoid segregation due to the gravitational field.…”

“…This technique has already been applied by various working groups in the field of biotechnology as well [1–5]. It was utilized for the separation of immobilized enzymes [6–8] and used for the isolation of target molecules [9–15]. In this process, the target molecule is specifically adsorbed on the functionalized particle surface in a reaction mixture and desorbed again from the magnetic particles (called magnetic beads) after magnetic separation has taken place.…”

Development of a novel disposable filter bag for separation of biomolecules with functionalized magnetic particles

“…On the other hand in a lengthwise alignment the assembly of the filter bag would be easier, due to a lower number of filament ends, which complicate the welding or sealing procedure. Furthermore the length of the matrix had to be taken into consideration: A matrix with longer filaments should retard a greater amount of particles . Therefore, a lengthwise alignment of the matrix filaments was chosen.…”

“…The wet density of the particles was adjusted to 1.20 kg·L −1 and the saturation magnetization to 40 A·m 2 ·kg −1 . The theory and simulation setup in the used CFD software (computational fluid dynamics) Comsol Multiphysics ® 4.3a is described in . The filter matrix was build up by aligning X by Y equal to 13 by 14 filaments on a rectangle cross‐section with a length of 200 mm in Z ‐direction.…”

“…Furthermore, the void fraction of the filter chamber influences the linear fluid velocity and thus also affecting the drag force of the fluid. In contrast to the fluid velocity within the filter chamber, which can be varied during operation, the magnetic force is constant during operation due to the separation apparatus and the filter matrix setup .…”