Magnetic activated cell sorting or MACS is a registered tradmark of Miltenyi Biotec company. This technique employs a dense column matrix in a magnetic field to capture magnetic particles. These magnetic particles are decorated with antibodies that can specifically bind to target molecules. The column matrix is composed of ferromagnetic spheres with a biocompatible coating. The column is placed into a magnetic field to allow for separation of the target molecule from unwanted molecules in solution.
The column is magnetized to retain magnetic beads
Following an incubation period where antibody-bound magnetic particles bind to target molecules, the solution flows through the column matrix within a magnetic field. The column is packed with ferromagnetic spheres that become magnetized in the magnetic field. This sets up a strong local magnetic field within the column. The purpose of this local magnetic field is to impede the progress of the magnetic bead-target molecule conjugates through the column. Meanwhile, unbound cells flow uninhibited through the column. The magnetic beads caught in the local magnetic field of the column are not chemically bonded to anything. Therefore, their immobilization is completely reversible once the external magnetic field is removed. Thus, they are easily collected after all unwanted unbound cells are washed out of the column.
Downfalls of column-based magnetic activated cell sorting
The MACS strategy results in slow separation times and complicated protocols including multiple washing steps. There is no real-time separation monitoring or quantitative assessment of the separation process, which can make troubleshooting difficult. There is no software available to allow comparison of the separation process to standard separation curves. Additionally, it is difficult to ensure batch-to-batch consistency.
Advantages of using a separation rack
Magnetic bead cell separation using separation racks such as those sold by Sepmag allow for faster and more quantitative magnetic separations. The column matrix is replaced with a separation rack. The separation rack provides a homogenous magnetic gradient throughout the solution for enrichment of target molecules without the need for multiple washings. Therefore the separation protocol is simpler and produces less waste. Additionally, a one-time purchase of a Sepmag separation rack is more cost-effective. Sepmag racks such as the Q100mL are accompanied by software that provides real-time monitoring of the separation process that includes standard curves for quality control across batches and protocols. For more information check this free PDF guide.