Reversible association/dissociation reaction of avidin on the dendrimer monolayer functionalized with a biotin analogue for a regenerable affinity-sensing surface

Anew approach to a repeatedly regenerable affinity-sensing surface was deve loped based on the reversible association/dissociation reactions between av idin and biotin analogues. For the affinity surface, a fourth generation po ly(amidoamine) dendrimer monolayer was first constructed on the 11-mercapto undecanoic acid self-assembled monolayer on gold. The dendritic surface ami ne groups then were functionalized with biotin analogues, desthiobiotin (1) , or newly synthesized desthiobiotin amidocaproate (2), an extended form of 1, which shows lower affinity toward avidin. To test the association/disso ciation reaction cycles at the affinity surface, avidin adlayer was formed onto the biotin analogue functionalized surface and displaced with free bio tin. To trace the stepwise reactions, biotinylated glucose oxidase (b-GOx) as a model enzyme was loaded onto the affinity surface, and cyclic voltamme tric measurements were performed by registering the activity of the associa ted b-GOx. The efficient association/dissociation reaction cycles were regi stered, especially for the a-modified electrodes, implying steric hindrance from the ligand length for biospecific interaction. With the optimized aff inity-surface construction steps and reaction conditions, continuous associ ation/dissociation reaction cycles were achieved, resulting in a regenerabl e affinity surface.