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Accelerating the Movement of Magnetic Beads

Because biomagnetic separation techniques are relatively simple, life science laboratories and industries are quite enamored with them. Indeed, using only magnetic beads and magnetic fields, biomolecules can be captured and extracted from complex media in magnetic bead separation. However, if this application is to be considered practical, it should also be faster than other separation technologies such as chromatography, electrophoresis or centrifugation.

 

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

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:

When there are small volumes (on the order of milliliters) and low viscosity suspensions, the separation is quite fast regardless of the biomagnetic separation conditions. When the volumes are large or the viscosity increases however, the time of separation can increase exponentially if inappropriate conditions are used. Furthermore, when non-homogenous biomagnetic separation devices are used, it is difficult if not impossible to replicate the optimal conditions when the volume is changed.

So how do we make magnetic bead separation faster without compromising the material?

Superparamagnetic beads have no magnetic moment when there is no magnetic field present. If one applies a magnetic field, it must be a field such that beads are saturated in that field and have a constant, fixed magnetic moment. In this case, the beads will act like small dipolar magnets and will interact with each other, forming chains. The higher magnetic moment of the chained cluster will cause the chains to move quickly in the direction of the magnetic gradient.

To decrease the separation time, the magnetic field profile should have:

  1. A field high enough to saturate the beads causing the above mentioned dipolar interaction and chain formation and,
  2. A steep magnetic field gradient.

Under certain conditions, chains formed in magnetic bead separation move faster than single beads

If both of the above conditions are fulfilled, the chains that form, which have a higher magnetic moment than single beads and proportionally less drag force, will move faster than individual beads in the exact same field. The trick is to optimize the field such that chains form, but aggregation is not a serious problem.

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:

 

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Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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