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sonication method, magnetic bead resuspension

The 2 Most Popular Magnetic Bead Mixing and Homogenizing Technologies

Today we’ll learn more about breaking up irreversible magnetic bead aggregates with different methods such as the sonication method, are you ready?

The sonication method is used to break up irreversible bead aggregates

This post is about resuspension techniques, such as the sonication method, and how they can solve magnetic bead aggregation. If you are interested in this topic, download our free ebook The basic guide for resuspending magnetic beads:

Download our Free Guide on magnetic bead resuspension HERE.

Mixing and homogenizing a magnetic bead suspension correctly after each step of coating and washing is the key to maintaining in-lot consistency. During the production process, the beads are resuspended several times in different buffers either while being coated with biomolecules, while capturing biomolecules or during washes. The beads should be homogenized completely in these buffers such that each small aliquot from the larger volume will be the same functionally. It is important that each aliquot have the same reactivity as any other aliquot from the same batch.

Mixing magnetic beads

Magnetic beads will drop out of solution and sediment over time. Because of this, magnetic beads should be mixed continuously. Mixing should take place even if aggregates are already present in the mixture. For small volumes (up to a few ml), a vortex agitator is a mixing option. Once you increase the volume and cannot use a vortexer, you theoretically have three options for homogenization: magnetic stirrers, rolling mixers and overhead mixers.

It is important to note that magnetic stirring is contraindicated for magnetic beads since the magnetized material would stick to the magnetic bars and be affected by the magnetic field generated by the stirring platform. The two mixing options that remain are rolling mixers and overhead mixers.

1. Rolling mixers

Unless the sonication method, rolling mixers can be used for homogeneizationRolling mixers accommodate cylindrical bottles that are typically lying on their sides (or horizontal). In this case, bottles are closed in order to prevent content from flowing out, as seen in the picture.

If you must have the bottle opened for your process, a tilted rolling mixer would be appropriate in order to minimize contact with the solution and minimize contamination.

2. An overhead mixer

Is the popular option when bioreactors are used. For an overhead mixer you will need to choose a shaft and blade that are not magnetic. Be very careful when choosing. Some grades of stainless steel are magnetic and even those grades rated as non-magnetic can be magnetized if they are not properly annealed after machining. Overhead mixing vessels can either be fixed in place or can be moved depending on the apparatus.

Once again, the choice of homogenization technology will be dependent on what is available for your use, your own experience and the nature of your process. Maintaining a good suspension with the appropriate technique will ultimately result in highly consistent results.

Don’t forget to check these posts from our blog in order to get a deeper insight into magnetic bead resuspension:

Dr. Lluís Martínez

The basic guide for re-suspending magnetic beads

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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