Magnetic-activated cell sorting (MACS)

introduction:

Magnetic cell separation has become a key method for isolating target cell populations from biological suspensions. This technique is required across a wide range of fields, including biology, drug testing, tissue engineering, cell-based therapies, clinical diagnostics, environmental applications, and fundamental biological research. In this section, we aim to discuss not only the applications of magnetic cell separation in clinical, industrial, and environmental contexts but also new and promising strategies in magnetic cell separation to address the challenges of isolating rare cells.

Magnetic-activated cell sorting (MACS) is one of the most widely used methods for cell separation.

In the MACS method, based on a cell-targeting principle, magnetic particles are specifically attached to a particular population of cells, followed by a physical separation process. In other words, during the physical separation stage, the target cells are collected on a column. The equipment required for this method is simpler, more straightforward, and less expensive compared to other methods. MACS can be performed using various approaches, including benchtop, manual, and automated methods. One of the advantages of using MACS for cell separation is that, on one hand, the implementation of these methods does not require a trained operator, and on the other hand, the MACS method takes less time for cell separation.

Different MACS methods include benchtop systems, manual systems (such as BioLegend MojoSort™, Invitrogen DynaMag™), and automated systems (such as Miltenyi Biotech autoMACS® and RoboSep from STEMCELL Technologies).

Manual cell separation tools in the MACS technique

Next, we will describe some cell selection strategies based on magnetic nanoparticles. Cell selection strategies based on magnetic nanoparticles include approaches based on cell surface markers, approaches based on DNA or RNA internalization, endocytosis-mediated labeling, and label-free magnetic cell sorting.

Approaches Based on Cell Surface Markers: The design of magnetic nanoparticles based on specific biological ligands (such as antibodies, proteins) and synthetic ligands (such as aptamers) aims to bind to target cell surface markers, leading to selective cell purification. Antibodies are one of the most well-known methods for selective cell purification. One of the advantages of using antibodies is their high specificity in targeting the desired cells.

Various strategies for specific cell separation with antibodies

Aptamers are single-stranded DNA or RNA oligonucleotides engineered for affinity and selectivity for a specific target molecule. They are synthetic compounds selected through a process known as SELEX. During SELEX, after aptamers bind to magnetic nanoparticles, a wide range of molecules such as proteins, microorganisms (including bacteria, viruses), and whole cells can be identified. Aptamers offer several advantages, including high affinity, low cost, and better stability compared to antibodies.

Another technique that MACS has introduced involves using peptides to bind to magnetic nanoparticles. Peptides are short chains of amino acids that, due to their small size, good chemical stability, and lower production costs compared to antibodies, offer significant potential as synthetic affinity ligands for biological separation. Peptides bind to magnetic nanoparticles (MNPs) through biotin-streptavidin interactions. MNPs have demonstrated a recognition capability in the field of cancer, such as breast, prostate, and liver cancers, with an efficiency of 90% and purity of 93% after binding to peptides.

Approaches Based on DNA or RNA Internalization: One method in this strategy involves transgenic techniques. Transgenic methods lead to the induction of expression of a surface marker that can be identified by a specific ligand bound to magnetic nanoparticles (MNPs).