Unspecific Binding in Reference Cell of Biotin CAPture chip

Dear SPR Community

At the moment I'm working for the first time with the Biotin CAPture chip from GE. It's a very stable chip when you have biotinylated ligands and makes is useful for many cycles without losing signal. However, it seems that in many cases, and especially at high analyte concentrations there is high unspecific binding in the reference cell.
It's manageable by e.g increasing the salt concentration of the buffer. However, the nonspecific binding is never fully gone and depending on the analyte it's high even at low concentrations.

Does anyone of you have the same problem when using the chip? Or does anyone know what's the reason for it? Does the DNA or the streptavidin somehow interact with e.g. antibodies as an analyte?
Also, would you know of some tricks to get rid of it?

Already thanks for reading my post and giving your thoughts about this

Best
Franchi

Dear Franchi,

You followed already the practice of adding some extra salt (250 mM) and detergent (0.02%).

What you can try is to add some CM dextran (0.005%) to the flow buffer and sample although I think the sensor chip is not dextran based.

Other suggestion (from the leaflet with the sensor chip) is to add some (sperm) DNA to counteract non-specific binding to the capture DNA.

And you can try to pacify the avidin on the chip by blocking it with D-biotin after your biotinylated ligand is bound.


Kind regards
Arnoud