The isolation of a specific cell population from a complex sample has become a common lab procedure. The availability of highly specific antibodies and the demand for targeted applications keeps on pushing the limits of the cell separation field. Thus far, three major techniques have been used for cell separation: centrifugation-based methods, fluorescence-activated cell sorting (FACS), and magnetic cell sorting. FACS and magnetic cell sorting offer the advantage of a more specific isolation, as they use antibodies to select the target population. However, they differ fundamentally in the way they work. So how does magnetic cell separation work?

Basically, specific antibodies that are conjugated to magnetic particles will bind to the cells expressing the target antigen. Applying a magnetic field will attract the cells towards the magnet, separating them from the rest of the cells. Alternatively, a 2-step separation process can be done. For example biotin-antibody conjugates followed by streptavidin-conjugated beads, or a similar approach, can also be used.

Frequently Asked Questions

Please review the following common questions to learn more about the MojoSort™ Magnetic Separation System, its properties, usage and applications. Contact our Technical Service Group if you need more information.

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What is the shelf-life of your magnetic particles?

1 to 2 years depending on product type.

What is the coating on your magnetic particles?

Hydrophilic polymers.

Can your magnetic particles withstand freeze/thaw cycles?

Not recommended, however lyophilized particles can be made available as a custom product.

What is the size of your magnetic particles?

The average diameter is approximately 130 nm.

What is the guarantee time of your magnetic particles?

A minimum of 6 months from the date of purchase.

Do your magnetic particles get internalized by the cells?

We have not determined this yet.

Are downstream applications affected by the magnetic beads bound to the cells?

We have tested mouse CD4 positive cells that have been isolated from the spleen and lymph nodes with directly conjugated Nanobeads, as well as CX3CR1 expressing cells from mouse bone marrow. The cells appear unaffected as assessed by migration, differentiation and stimulation assays.

Will your magnetic particles separate well in other company’s magnetic separation systems?

It is possible that other magnetic separation systems can be used. To learn more about this please contact our Technical Service Group.

Do you provide a custom conjugation service to your magnetic particles?

Yes, we do. Please contact our Custom Solutions Team at cst@biolegend.com.

Is there a way to detach your magnetic particles from the cell surface?

No, not currently.  We have found that cells are functional without the need to detach the magnetic Nanobeads.

What is the storage buffer of your particles?

The particles are stored in a neutral pH solution containing BSA and sodium azide.

Can your magnetic particles be sterile filtered?

Yes, they can be sterile filtered as the particles are smaller than 0.22 µm.

Can I stain positively sorted cells by flow cytometry?

Yes, this is possible, but if you are staining for the same marker as used for sorting, we would recommend using a different clone with non-overlapping epitopes.

Are there any clone restrictions when checking the purity of isolated cells?

There are no restrictions for negatively selected cells, as they are untouched by antibodies. For positive selection, there may be clones that are less efficient than others due to possible epitope competition. Please refer to the Technical Data Sheet or contact the Technical Service Group for advice.

Are your magnetic particles suitable for use with whole blood?

We have not tested this application yet.

What is the composition of your MojoSort™ Buffer?

The diluted, 1X MojoSort™ buffer contains 1X phosphate buffer saline (PBS) supplemented with 2 mM EDTA and 0.5% BSA. The 5X solution is sterile. To preserve sterility dilute with sterile water under sterile conditions.

Do you offer your base magnetic particles (i.e. without any streptavidin or antibody conjugation)?

No, not currently.

Are MojoSort™ Nanobeads compatible with other commercially available magnetic separation systems?

MojoSort™ magnetic particles can be used with other commercially available magnetic separators, both free standing magnets and column-based systems.  Because MojoSort™ protocols are optimized for the MojoSort™ separator, the protocols may need to be adjusted for other systems.  Please contact BioLegend Technical Service for more information and guidance.  We do not recommend using MojoSort™ particles for BD’s IMag™ or Life Technologies’ DynaMag™.

What antibodies are present in the depletion cocktails provided for isolation kits?

Please contact our technical service team for further assistance.

Separation of cells can occur via “Positive Selection” or “Negative Selection” (also known as “Negative Depletion”). This depends on whether the bead-bound antibodies directly target your cells of interest (positive selection) or target unwanted cells (negative selection). Either way, both separated fractions of cells can be used for downstream applications.

Line graphs show the size distribution of BioLegend’s MojoSort™ Nanobeads, and the distribution of 4 other commercially available magnetic particles. BioLegend’s average size is 130 nm, with a narrow and consistent distribution to ensure consistent performance.

MojoSort™ Mouse CD4 T Cell Isolation Kit

A single cell suspension from pooled C57BL/6 mouse spleen and lymph nodes was prepared to isolate CD4⁺ T cells using the MojoSort™ Mouse CD4 T Cell Isolation Kit. Cells were stained with PE anti-mouse CD4 (clone RM4-4), APC anti-mouse CD3ε (145-2C11), and 7-AAD. Dead cells were excluded from the analysis.

MojoSort™ Human CD4 T Cell Isolation Kit

Human PBMC were pooled from three healthy donors to isolate CD4⁺ T cells using the MojoSort™ Human CD4 T Cell Isolation Kit. Cells were stained with PE anti-CD4 Antibody (clone RPA-T4), APC anti-mouse CD3 (UCHT1), and 7-AAD. 

CX3CR1⁺ Cells Migrate Back to the Bone Marrow After Adoptive Transfer

CX3CR1⁺ cells were isolated from C57BL/6 mice bone marrow using a two step separation protocol. Total bone marrow cells were incubated with directly conjugated Ly-6G Nanobeads to deplete granulocytes. After depletion, the resulting fraction was incubated with biotin anti-mouse CX3CR1 antibody followed by MojoSort™ Streptavidin Nanobeads, resulting in a population containing about 70% of CX3CR1-expressing cells. The cells were then labeled with CFSE and injected back into recipient C57BL/6 mice. Three days later, CFSE⁺ cells are found in the bone marrow of the recipient mice. Control mouse represents an animal injected with PBS.

Due to the properties of our magnetic nanobeads, it is possible to use them in commercially available separation columns. We have validated their use with such devices through internal research, and confirmed at academic labs. It is also possible to use them in column-based automatic separation machines. Thanks to their strong magnetic properties, the number of beads needed to separate the cells may be far lower than particles from other commercial suppliers. Thus, to use MojoSort™ Nanobeads in commercially available columns, a dilution is recommended. Click in the corresponding buttons for Positive or Negative Selection Protocol and follow the instructions as a guideline for optimal results. If you need further assistance please contact BioLegend Technical Support.

Positively Selected Cells

MojoSort™ Nanobead-isolated CD19⁺ cells using columns do not display more bound beads on the cell surface (A) as compared to cells isolated with a compatible commercial product using the same columns (B). Red arrows indicate where the particles are located. Numbers indicate either 2 or 3 magnetic particles adjacent to each other. Pictures were taken at the same magnification, scale shown in B. Images are representative of 41 different cells each.

Negatively Selected Cells

CD4⁺ T cells Isolated with MojoSort™ CD4 T Cell Isolation Kit using columns do not display particles in the cell surface. Image is representative of 36 different cells.