Filtration is a simple technique used to separate solid particles from suspension in a liquid solution. There are many filtration methods available, but all are based on the same general principle: a heterogenous mixture is poured over a filter membrane. The filter membrane has pores of a particular size. Particles larger than the pores will be unable to pass through the membrane, while particles smaller than the pores will pass through unhindered. Additionally, all liquids will pass through. The final result of a filtration process is a collection of residue on the filtration membrane. This residue is therefore effectively separated from the rest of the mixture that passed through the membrane.
The traditional way to check whether a biomagnetic separation process is complete is by sight. The technician/researcher looks at the suspension: at the beginning of the process, the suspension is homogenous and opaque, but when the separation process is complete, the magnetic beads are left on the walls of the vessel and the supernatant is transparent. When the suspension is ‘transparent’, the technician stops the process by extracting the supernatant, leaving the magnetic beads in the bottle.
Magnetic bead kits are widely used in bioscience laboratories nowadays, as their development and perfecting during recent years has been significant. Both scientists in research labs, for immunoassays and magnetic separation processes, and lab technicians in hospitals, using IVD kits for molecular diagnostics, have experienced an improvement in their separation processes due to these magnetic bead kits. As using a biomagnetic separation process has proven useful for these applications, the increasing demand in magnetic beads has lead providers to develop cost-effective ways for their production.
When new magnetic beads reach the market, one of the questions users have is, how well will it separate?
End product variability is caused in large part by resuspension problems in your process. During a magnetic separation process, the retention forces in the system need to be high enough that losses of the beads will be avoided when the buffer is pumped out. But the forces should not be too great because if they are excessive, beads will aggregate.
Large magnetic systems create potentially high risk environments in terms of safety during a magnetic separation process. These systems generate large magnetic fields which result in the generation of large stray fields. The stray fields affect the surrounding environment and can attract ferromagnetic objects, potentially injuring system operators. The larger the system, the higher the risk, especially if workers do not follow Health and Safety protocols.
The concentration of magnetic beads is an important step in a magnetic separation process. Separation time is dependent on magnetic bead concentration, and final kit performance is also very dependent on accurate concentrating techniques, but liquid handling inaccuracies can lead to serious errors. If these concentration errors are not detected early in the process, excessive time, money and effort will need to be spent to either correct or redo the batch.
Learning more about the behavior of magnetic beads separation when strong magnetic fields are applied
When one scales up production using a classic magnetic separation system, one finds that the separation time increases quickly with an increase in production volume. An increase in separation time means that material losses are higher and aggregation problems become a serious problem. By using homogenous separation time, one finds that the magnetic separation process is shorter and the separation time can be easily estimated. In homogeneous systems material loss and bead aggregation is minimized.
In the Life Sciences, one of the most critical parameters for final IVD kit performance is magnetic bead concentration. The beads are functionalized before the magnetic separation process with antibodies or other biological molecules, so the concentration of magnetic beads also delivers a specific concentration of biologically active reagent. If you do not have the correct amount of beads/biological molecules in your preparation, the sensitivity of the kit changes significantly. Therefore volume control of the suspension is quite important.