Irreversible aggregation is one of the main concerns when functionalizing magnetic beads for use in diagnostic and biotech applications. The presence of aggregates can cause high variability in the functionality of the magnetic beads and large inconsistencies. Irreversible aggregation causes serious problems when one tries to resuspend the particles after the processing, coupling and washing steps. Because of this, as we have explained in previous posts, one of the best ways to solve this issue is using the sonication method.
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:
The two main factors that cause irreversible aggregation of magnetic beads
Irreversible aggregation of magnetic beads results from two main factors:
1. Sustained exposure to high magnetic forces
Problems with exposure of the beads to high magnetic forces over a long period of time can also cause aggregation, regardless of the coating efficiency. Excessive magnetic forces on the beads in the retention area may overpower the inherent electrostatic repulsion between the beads.
The effect is exacerbated when separation times are long since the first beads to arrive in the retention area will be exposed to high forces over a long period of time.
2. Not following the correct protocol
If researchers do not follow the appropriate steps to avoid irreversible aggregation after each of the processing steps (coating, conjugation and washing), the clumps will ultimately limit the available bead surface and generate functional variability.
Even worse, aggregates will act as larger beads during magnetic separation, completely changing the dynamics of the process. Aggregates will reach the retention area much faster than the calculated time to retention of non-aggregated beads.
If aggregates are not dealt with during the magnetic bead processing steps, the best case scenario is that the variability of the final aliquots will be high. In-lot consistency is greatly compromised. In the worst case scenario, if variability is too high, the entire production lot may need to be discarded, wasting time, effort, resources and money.
If aggregate formation during processing is unavoidable, it is important to include methods such as the sonication method to break apart the aggregates after each processing step.
Don't forget to check these posts from our blog in order to get a deeper insight into magnetic bead resuspension:
- Five Points to Consider When Using Sonication Methods on Magnetic Beads
- The Four Main Limitations of using the Sonication Method in Magnetic Bead Suspensions
- Mixing and Homogenizing Magnetic Beads without Touching the Suspension