desthiobiotin-labeled particles were enriched by streptavidin-coated magnetic beads in this study. Exosomes are eluted from beads by the application of a high concentration of biotin. This is a typical streptavidin/avidin-biotin affinity chromatography application. Desthiobiotin is replaced with biotin in seconds due to the high concentration of biotin. Desthiobiotin is a biotin analog that binds less tightly to biotin-binding proteins and is easily displaced by biotin. Both of the component has streptavidin binding affinity but a high concentration of biotin in this case represents a binding competition and replacement occurs between biotin and desthiobiotin.

In summary, high concentration and minor affinity differences are the keys to competitive binding herein.