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Posted on Thu, Jan 24, 2013

The 6 key factors affecting the behavior of magnetic beads

There are 6 factors affecting magnetic bead separationBiomagnetic separation technology is being widely adopted in many biotech and other life science industries. The managers of these industries spend a lot of energy, time and resources choosing the correct beads for their applications, however they often overlook very important variables that need to be controlled pertaining to the magnetic bead separation process.

Problems with field and force, magnetic strength and bead aggregation tend to make the separation process difficult to reproduce and, ultimately, difficult to scale-up.

This post is about magnetic bead separation and how to validate this process. If you are interested in this topic, and are willing to learn more about it, download our Free Guide The Starting Guide to Validate Biomagnetic Separation Processes:

Free PDF guide:   "Validation of Magnetic Bead Separation Processes" 

Factors affecting the behavior of magnetic beads

There are six key factors affecting the behavior of magnetic beads that are necessary to observe and control:

  1. The viscosity of the buffer. Viscosity has a direct effect on the speed of the bead because the magnetic force acts against the drag force.
  2. Ionic force and pH of the buffer. These will affect the surface charge and the stability of the suspension.
  3. Temperature. This parameter can affect all of the other factors.
  4. Magnetic content. The magnetic force will depend on how magnetized the beads are.
  5. Bead size. Drag force depends on the size of the beads, so the size distribution (bead diameter) will have an impact on the drag force.
  6. Homogeneity of magnetic force.

Likely, managers are already controlling factors 1 – 5, but the magnetic force itself is often overlooked. Is optimal magnetic force applied to your beads? Are you applying a homogeneous force to all of your beads?

If traditional magnetic separators are used, the magnetic force is dependent on the distance to the magnet. Therefore, beads at various distances from the magnet will experience non-homogeneous fields and forces. Some beads will reside in the magnetic saturation regime while other beads will travel back and forth between weaker and ber magnetization fields.

Furthermore, beads farther from the magnet are harder to attract because of the low magnetic force surrounding these beads. On the other hand, beads closer to the magnet experience excessive forces for longer periods of time, resulting in bead aggregation, loss of bead activity and resuspension problems.

When beads aggregate, there is less viable bead surface area, the biomaterial to bead interaction is reduced, the biomaterial to biomaterial interactions become ber and end product variability becomes a real problem. More time-consuming sonication and washing steps are needed when this happens. It is clear that not only understanding the material, but the process as well, is important to a company’s bottom line and the consistent good quality of the end product.

Non-homogeneus magnetic bead separation problems

If you found this article interesting and want to get a deeper insight in the topic of magnetic bead separation, make sure to check these articles from our blog:

Dr. Lluís Martínez

biomagnetic separation processes

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