Magnetic separation has been an emerging technology in the recent decades in biomedical science and industry in which magnetic property and behavior – known as “magnetism” – of micro/nano-sized particles are employed for the separation of macromolecules of interest (e.g. nucleic acids, proteins, peptides etc) from biological samples or chemical suspensions.
Sometimes during biomagnetic separation in a magnetic separation rack, different steps in the process require using different volumes. For example, if you have produced a ‘mother batch’ of magnetic beads and this large batch needs to be aliquoted so that each aliquot of beads can be uniquely coated, you will need the ability to move easily between volumes.
Although separation time may be one of the most obvious parameters to validate in your magnetic separation rack production, it is certainly not the most critical. Classical magnetic separation rack use non-homogeneous magnetic separation. When scaling up production on these devices, larger volumes can lead to longer and longer separation times.
Any small magnetic separation rack (i.e. the types used to develop a prototype product before scaling up) generates magnetic fields that decay rapidly with distance. However, scaling up the process can be problematic because the size of the classical magnetic separation rack itself grows rapidly with desired batch volume. Because the magnetic field profile and the magnetic force are not the same in a larger device, the safety of users and the safety of ancillary equipment can become a serious issue.
Electromagnets are the classical way to generate intense magnetic fields. If you apply the electrical current across a coil, the magnetic field is quite small. But if you wrap the coils around an iron yoke, you can generate much stronger magnetic fields. Unfortunately, if you need to scale up a magnetic separation process, you also need to increase the electrical power to the magnetic separation rack and the amount of iron and copper used for the coil.
A very common problem that occurs when scaling up non-homogeneous magnetic separation processes in a magnetic separation rack is irreversible aggregation of the magnetic beads. When the process is scaled up, the magnetic force experienced by the beads closest to the magnet is very high.
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When using a standard magnetic separation rack, often you will experience a decrease in bead and biomolecule yield when scaling up your production process. This causes the scaled up process to be less economically efficient than it could be with yields commensurate to your original production.
Classic magnetic separation rack devices are designed such that both the magnetic field gradient and the magnetic state of the beads vary with the position of the beads. This means that once a process has been validated at a specific volume (i.e. your process has low material losses and no irreversible aggregation), it is difficult to change batch size without needing to re-validate the process.
Any small volume classic magnetic separation rack is relatively cheap and does a fairly good job at separating magnetic beads. However, if the process involves multiple instances of capture and elution steps, irreversible aggregation becomes a real problem. In small volume separations (i.e. on the order of milliliters), using the appropriate techniques can give you excellent re-suspension results.
When new magnetic beads reach the market, one of the questions users have is, how well will it separate?
In a standard magnetic separation rack, scaling up to a larger lot volume usually creates four common problems:
The most frequent concern when considering the use of modern Biomagnetic Separation Systems is their compatibility with specific magnetic beads. Although Sepmag® devices are already working successfully in IVD labs and production lines, this is a very legitimate question.
It is vitally important to understand the process and all of the variables of the process when scaling up a biomagnetic separation in a magnetic separation rack. If you do not understand the details of your process, you will throw away your initial investment you made in validating your initial process and jeopardize the product’s time to market.
The most common mistake when attempting to scale up production of magnetic beads using a classical magnetic separation rack is to use the same magnetic field that was used at smaller volumes. But keeping the magnetic field constant at different volumes will not give you the same results because the separation conditions are completely different.
Sometimes companies scale up production in a magnetic separation rack in order to produce large quantities. However, for validation batches or new processes, they may not need to work at the large scale level. In addition, different steps of the process may require different volumes. For example, if you are producing a large ‘mother batch’ of magnetic beads, different portions of that ‘mother lot’ may be used for unique coatings. Another example is when small validation lots of a product need to be produced before launching full scale production of the product.
The main consumers of magnetic beads are In Vitro Diagnostic (IVD) companies who utilize these materials for their kits. Since some of these companies are highly successful, as they obviously need to cope with higher demand for their kits by increasing production in a magnetic separation rack.
When you decide to scale up your process, one of the most difficult parameters to determine in a non-homogeneous magnetic separation rack is the separation time. In scaled-up non-homogeneous devices, you must use longer separation times in order to gain the same bead yield as a smaller process. However, it is still difficult to determine when the separation is complete.
When you have systems that have large standard open magnets that can generate stray fields, such as a non-homogeneous magnetic separation rack, the devices can be very dangerous. The magnetic fields generated all around the device and are known to have caused laboratory accidents in the past. Scaling up a process means that the stray fields will increase quickly with the size of the device.
Working with a magnetic separation rack, at small volumes it is easy to create and use a quadripol electromagnet to generate high forces during biomagnetic separation processes, even to the point of making the process very close to homogeneous. The main advantage to using electromagnets for this type of process is the ability to easily modify the current passing through the magnetic coils, thus modifying the value of the magnetic field and force during the setup of your process.
When companies desire to increase the volume and scale up their production using a non-homogeneous magnetic separation rack, they use higher magnetic forces in order to separate the biomagnetic beads. As a result, the forces experienced by the beads nearest the magnet are extremely high. In addition, the time of separation also needs to be increased substantially when the volume is increased in order to collect an acceptable percentage of beads in a non-homogeneous system.
During non-homogeneous separation in a magnetic separation rack, in order to generate a magnetic force, you need to use magnet arrangements to create a variation in the magnetic field. In this situation, the magnetic force will always vary with distance from the magnets.
When a non-homogenous magnetic separation rack (a classical system) is used for scaling up a process, the conditions for a larger batch will completely change from the smaller batch. In these classical non-homogeneous magnetic separator, both the magnetic field gradient and the magnetic state of the beads (either linear or saturated) will vary depending on their position and relative distance to the magnet.
While it might be thought that ‘bigger is better’ during a scale-up process, merely using a larger magnet in a magnetic separation rack for larger volumes generates very different conditions. This leads to inconsistencies and other problems with the final product.
Working with magnetic separation rack? Keep reading!
Do you want to learn how to take the most of your magnetic separation rack? There are lots of common mistakes related to the scale-up of biomagnetic separation processes, and lots of them imply the use of non-homogeneous magnetic racks.
When biomagnetic particle kits are initially developed, R&D companies work with small volumes in a magnetic separation rack in order to test and optimize a number of variables. When the kit is deemed successful, the company obviously wants to take the kit to market and consequently ramp up production.