Biomagnetic Separation has numerous applications in Life Science. From cell sorting to molecular diagnostics, this technology can be used with volumes ranging from a few nanoliters (lab-on-chip) to tens of liters (production of IVD-reagents).more
To control the process, technicians rely on the fact that the magnetic bead suspension is usually dark. During the separation process, the solid phase moves to the retention area and the buffer becomes transparent. This makes it clear when the process has finished either by sight or, when more precision is required, using a spectrometer.
The main limitation of these approaches is that they only allow analysis of the final result, telling us whether the separation is complete after a given time. A visual inspection provides no information about what happened during the process and it is not possible to detect a faster-than-expected process if the separation time is fixed.
For technicians using traditional magnetic separators, real time-monitoring was not an issue, given that this kind of information would be very difficult to interpret. Because the magnetic field and the gradient change depending of the position of the magnetic bead it is difficult to analyze changes in the process dynamics. Variations in magnetic behavior due to changes in the suspension/beads are different at different points in the working volume, making the data difficult to interpret.
However, when a biomagnetic separation system with constant magnetic force is used, the information provided by real-time monitoring is far easier to analyze. Because the contribution of the applied field pattern is the same throughout the working volume, magnetic bead dynamics depend directly on magnetic moment and diameter (the latter affects the drag force). Changes in the viscosity of the buffer caused by variations in temperature or composition are clearly visible because the separation speed changes. Continuous monitoring also makes it possible to optimize protocols with curves that can be extrapolated and the results can be extrapolated to different concentrations and the interaction between the beads can be studied.
When the biomagnetic separation process is transferred from the R&D laboratory to the production facilities, Quality Control becomes a major concern. Validation of the process conditions is the first issue, but when a homogenous magnetic force is used this is not a problem. Once the value of the force has been tested in R&D or during the validation stage, the production system is given similar values to guarantee that there are no losses or irreversible aggregation problems.
With constant force systems, the separation time can be adapted to the new vessel diameter. Given that the speed is proportional to the magnetic force, the time needed for the farthest beads to reach the retention area is t=distance/speed.
However, in production processes, use of the separation time alone involves a risk of approving faster batches than those validated, because the suspension transparency will be correct at the separation time. For example, if magnetic beads are aggregated before starting the separation, the batch might appear to be correct, but the resulting product would cause quality issues in subsequent steps of the manufacturing process.
When the separation process is monitored, the situation is different. Among the quality issues detectable through real time monitoring are bead aggregation, incorrect concentration, variations in bead diameter and magnetic charge, buffer viscosity changes (caused by incorrect composition or by differing temperatures).
To conclude, even if biomagnetic separation users have not traditionally monitored the process, they are important reasons for doing so at both R&D and production level. In the past, the main constraint on monitoring was the lack of controlled conditions for the process. Using advanced biomagnetic separation systems with a constant force throughout the working volume overcomes this limitation and makes it possible to benefit from the information provided by real-time monitoring.