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blocking elisa

blocking solution in elisa

blocking solution elisa

elisa blocking reagent

elisa plate blocking

protein binding surfaces

nonspecific binding cross-reactivities

minimizing nonspecific binding

Plate Blockers


The surface of plates is charged to maximise the attachment of the coated antigen or antibody. Even with the most dense coating with the desired molecule, the surface will keep sufficient free binding spots. Without surface blocking the assay antibodies and other analytes will bind to the surface of plate, thus producing false positive results and the background signal (that is sometimes hard to discriminate from low level reactions). This should be prevented in order to obtain the reliable assay.

Description & Properties

Blocking of the plate is required to saturate all free binding spots at its working surface. This can be achieved by treating the surface with charged neutral (in relation to the assay components) molecules. Aptum offers four different types of blocker buffers that include their classic variants and the unique NXR-Block (No Cross- Reactivity) which is the most advanced and widely applicable blocking buffer.


A classic BSA-based blocking buffer that has its limitations, but habits of assay developers and some tradition on its side. It is, indeed, a well established blocker for many applications.

The high purity controlled raw material used for this buffer guarantee the consistency of this product and no lot-to-lot variations.

However, if you do see background despite use of BSA-based blocker, we would recommend other types of blockers for your particular application. Also, if you are developing a new assay, we would recommend you first try other, more reliable, types of blocking buffers


A premium casein based blocking solution for routine applications. It is based on chemically purified and fragmented high purity casein. This CS-Block is not comparable to other commercially available and/or home made casein based solutions, produced by just dissolving and filtrating casein.

Comparing to BSA-based blockers, CS-Block provided an impressive reduction in coefficient of variation in assay (up to  3 times), which increases the reliability of results of the assay based on CS-Block.

It is recommended for industrial-scale production of immunodiagnostics, but also for commercial and research applications of other assays, such as protein array and Immuno-PCR.


A protein-free blocking buffer, where the charged blocking molecules of non-protein nature are used to saturate the plate free binding sites. It ihas been specifically designed and recommended for antigen-capture assays.


A peptide-based blocking solution that is the most advanced type of the plate blocker that we recommend for antibody detection assay and other types of assays. In contrast to other classic types for blocking buffers this one produces no steric effects, affecting the recognition by analysis of the absorbed antigen or antibody simply due to them being masked by large protein molecules. The blocking peptides also bind to more areas of the pate, being more accessible for the tiny sized molecules.

Ordering codes

A-Block                  Ready-to-use               125 ml                      #AP0517-125

                                                                    500 ml                      #AP0517-500

CS-Block                Ready-to-use              125 ml                      #AP0514-125

                                                                    500 ml                      #AP0514-500

PF-Block                Ready-to-use               125 ml                      #AP0515-125

                                                                    500 ml                      #AP0515-500

NXR-Block             Ready-to-use               125 ml                      #AP0516-125

                                                                    500 ml                      #AP0516-500

Using Plate Blockers (general guide)

- Add Block buffer 200 μl/well

- Incubate 1 to 2 hours at room temperature

- Wash 3-5 times with 200-300 μL of  Plate Wash, 1x buffer

Important: most of the time you may immobilize the required assay molecule on the plate, block the plate, wash it, and then perform the coating stabilization.

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