Sodium azide is a preservative used to inhibit the growth of contaminants, such as bacteria or fungi, and therefore maintain the life of the antibody for a longer time. However, its presence in these antibody solutions may affect its use in cell culture assays as it is toxic to cells. It can also interfere with antibody conjugation and inhibit the activity of horseradish peroxidase enzyme (HRP).

Many antibodies contain sodium azide, information that you can find in the technical data sheet of the product. If the antibody is to be used for cell culture assays or conjugation, it is recommended to remove sodium azide from the antibody solution.

Sodium azide will interfere with any conjugation involving an amine group. Therefore, it must be removed before continuing the conjugation. After conjugation, the antibodies can be stored in sodium azide if desired.

You can do any of the following 3 methods to remove sodium azide from your sample:

    A dialysis unit can be used to remove sodium azide from samples from 0.1 ml to 70 ml in volume.

It is important to note that some protein loss will occur during adherence transfer to surfaces.

Using a semipermeable membrane, you should bear in mind that the molecular weight of sodium azide is about 65 Da. Therefore, a dialysis unit with a limit of between 12 and 14 kDa should be used. This will allow azide to pass through the membrane, but the antibody and any protein present in the buffer will be retained.

It is recommended that, before starting the procedure, the materials are sterilized and the resulting preparation is handled aseptically. Furthermore, because the preservatives are removed from the antibodies during the process, it is important to keep the sample in cold conditions so that it does not lose its function.

Perform hydration of the membrane with a corresponding dialysis buffer. For example: PBS, TBS, or HEPES (pH range 6–8).
The dialysis unit must contain at least 1L of buffer (per ml of antibody) against which the antibody is to be dialyzed. It is recommended to make at least 3 buffer changes.
Dialyze on the magnetic stirrer for at least 1 hour on each change. Some protocols even recommend 3-6 hours

Advantages: It can be performed with dialysis tubes for large quantities or by centrifugation for small samples.
Disadvantages: The most significant disadvantage is that it is a time consuming process. In addition, some protein loss may occur during adherence transfer to surfaces.

    This method involves the use of a column that allows low molecular weight molecules to pass through the membrane. Using a microcentrifuge, the membrane traps the antibody, which will then be eluted using a buffer.

Advantages: The kits are readily available commercially. Simple method following the manufacturer’s instructions.
Disadvantages: Some protein loss may occur during transfer due to adherence to surfaces.
You can contact us for information about our antibody purification kits.

    This procedure is suitable for smaller volumes (1 to 3 ml). Desalination resins are made up of small particles with different pore sizes that perform size exclusion.

This size exclusion is a method used to separate molecules in solution by their molecular weight. Variable molecular weight particles will elute at different rates.

For example, a Sephadex G25 column system or equivalent will allow sodium azide to be effectively removed from an antibody sample.

For this technique, it is recommended to follow the instructions for use of the column according to the manufacturer. The antibody will finally be found in the eluted product, located in the collection tube.

Advantages: Pre-packed Sephadex spin columns are readily available and can be used for this procedure.
Disadvantages: Some protein loss may occur during transfer due to adherence to surfaces.

In addition, another recently studied technique is the treatment of sodium azide solution by means of a heterogeneous Fenton process in the presence of natural laterite as a catalyst. Experimental results showed that laterite was a suitable alternative to typical ferrous salts: Khataee, A. and Pakdehi, SG (2014). Removal of sodium azide from an aqueous solution by a Fenton-like process using natural laterite as a heterogeneous catalyst: kinetic modeling based on nonlinear regression analysis. Journal of the Taiwan Institute of Chemical Engineers, 45, 2664-2672. https://doi.org/10.1016/j.jtice.2014.08.007

In the event that you do not have time to carry out this type of procedure, we also have antibodies free from sodium azide, you can consult the catalog with this type of products at this link.

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