Attaching a protein to a bead can be a detailed process that requires forethought and careful planning. Generally, a molecule is attached to a particle through a surface group available on the coating of that particle, for example in the case of streptavidin beads. In cases where the attachment is covalent, it is essential to choose a binding site on the molecule that will allow for proper orientation, maximally presenting the desired site to the sample while still retaining a strong attachment between the molecule and the bead.
This post is about choosing the right platform for a given biomarker. If you want detailed information about this topic, download our free ebook The Advanced Guide for the use of Magnetic Beads in Chemiluminescent Immunoassays:
In what cases should I use beads with plain coatings?
In some cases, it might be more advantageous to utilize beads that have plain coatings, i.e., beads that do not contain any surface functional groups or biolinks. Situations that might warrant utilizing beads with plain coatings include cases where the orientation of the protein is not an issue. Alternately, if some loss of protein due to stability issues can be afforded, or if the amount of conjugate is not a limitation, it might be beneficial to forego the development of a specific binding strategy and simply allow the bead to attach a molecule through passive adsorption. This approach is generally much simpler, requires less planning, and necessitates less troubleshooting.
The limitations of plain coating
There are limits to passive adsorption, however. While using beads with a plain coating might be acceptable for certain applications, attaching a molecule to these beads yields no control over the final orientation of the bound molecule. Moreover, the binding is non-specific and, as such, the attachment protocol is less efficient. The decision to utilize beads with a plain coating will ultimately have to be made by weighing the simplicity and ease of passive adsorption against more time-consuming, but ultimately more specific and efficient types of attachments.
Don't forget to check these posts from our blog in order to get a deeper insight into magnetic beads and immunoassays:
- Using streptavidin magnetic beads in Chemiluminescent Immunoassays
- Finding the Know-How Necessary for In-House Expertise
- Magnetic Beads: What is the Right Coupling for a Specific Biomarker?