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streptavidin beads

How to Select the Best Surface for Your Chemiluminescent Immunoassays

Depending on your antibody and your assay, you have a number of ways to couple your protein or antibody to the surface of your magnetic beads. Once again, forethought is important in choosing which bead surface to use. Plain surfaces, modified surfaces or pre-activated surfaces in streptavidin beads are examples of these possible choices.

Streptavidin bead surfaces is important in CLIA

This post is about using magnetic beads, such as streptavidin beads, in Chemiluminescent immunoassays. If you are interested in this topic, download our free ebook The Basic Guide for the use of Magnetic Bead in Chemiluminescent immunoassays:

Free PDF guide:  "The Basic Guide for the use of Magnetic Bead   in ChemiLuminiscent ImmunoAssays (CLIA)" 

Plain surface

This is the cheapest alternative and allows you to coat your beads passively. If, however, you are experiencing a great deal of non-specificity and background problems, you may need to consider the modified alternatives below.

Modified surface

This is the simplest of the surface modifications that allow you to covalently and stably couple your antibody to the magnetic beads. Carboxyl, amino, hydroxyl and sulfates are typical groups that are added to the surface. Some problems can occur such as aggregation and nonspecific binding. If these problems are an issue, you may need to use pre-activated surfaces.

Pre-activated surface

These surfaces are very ‘sticky’ and also allows for very stable covalent coupling of your antibody to the beads. Activated groups used are tosyl, epoxy, and chloromethyl groups. These are also very easy to couple by incubating the pre-activated beads in the correct buffer, correct pH or other conditions and coupling is automatic.

Bio-activated surface

This is a very expensive, but highly effective option. A coat such as streptavidin is placed on the magnetic beads and the bead bound to the analyte can easily be removed from any background noise or free antigen merely by using biomagnetic separation. No additional washes are necessary.

Encapsulated surface

The beads are encapsulated in a ‘shell’ structure. These beads give a very low non-specific background reading, improved sensitivity and improved colloidal stability.

Magnetic beads can have different surfaces, such as plain surfaces, or activated surfaces in streptavidin beads

By choosing the correct surface for your beads you can determine the sensitivity and accuracy level of your CLIA. For very high resolution/sensitive assays, the better the surface, the better the results.

Don’t forget to check these posts from our blog in order to get a deeper insight into Chemiluminescent immunoassays:


BIO Dr. Fabrice Sultan

streptavidin beads ebook

Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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