Category: Automation and High-Throughput Technologies
The use of high gradient magnetic fields for the separation of particles is commonplace in the fields of immunology, proteogenomics, molecular biology, and other bio-medical industries. Target particles, comprising entities such as DNA, RNA, proteins, and other bio-molecules, may be isolated from a solution by the use of magnetic beads. These beads are stored in an open reagent trough until they are aspirated via pipette to the microtiter tray used to run the test, (assay). During this time, which can last a few minutes, the beads will fall out of solution, which results in and incorrect bead concentration, which will negatively affect the assay results. This incorrect concentration will also lead to waste, as the bottom one-third of the trough will have a very high bead density which may not be able to be used in the assay. Therefore, the beads may need to be resuspended via methods such as shaking of the reagent trough or pipette tip mixing, which can be inconsistent and increase overall assay time. In addition, mechanisms to verify that the magnetic beads have been suspended into solution are very uncertain. Verification has mostly consisted of subjective techniques, such as visual observation or by choosing a tip mixing duration time based on the successful results of the protocol, derived during assay development.
We have developed a prototype device to keep the beads suspended in solution in a reagent trough and allows for the bead concentrations to be quantitatively verified. The device consists of a base which holds a reagent trough containing the magnetic beads in solution. A magnet assembly is mounted to a carriage that is axially movable along a track, which is in line with the reagent trough. As the magnet assembly moves back and forth along the outside of the reagent trough, a magnetic field and field gradient moves along with the magnet, causing agitation of the beads. This agitation causes the magnetic beads to remain in suspension in the reagent trough, or it resuspends them if they have already begun to fall out of solution. The device is self-contained and can mount on the deck of, (and be integrated to), an automated liquid handling system. It can easily be modified to accommodate a variety of reagent troughs used throughout the life sciences field. The movement of the magnet assembly is automated and electronically controlled, so that unique motion protocols can be developed based on particle size and concentration. The device can verify that the beads are properly suspended through the use of a sensor, which is integrated to electronic controller. The device could also be used on the bench-top for use with manual assays.
Christian Kronshage– Product Development Engineer, R&D Engineering, Elk Grove Village, IL