Noncovalent Immobilization of Proteins on a Solid Surface by Cucurbit[7]uril-Ferrocenemethylammonium Pair, a Potential Replacement of Biotin−Avidin Pair

A novel noncovalent method to immobilize a protein on a solid surface using the cucurbit[7]uril (CB[7])-ferrocenemethylammonium ion (FA) pair, which exhibits exceptionally high binding affinity (K ≈ 1012 M-1), is reported. This method involves (1) anchoring CB[7] units on an alkanethiolate self-assembled monolayer (SAM) on gold, (2) attachment of FA units to a protein to be immobilized, and (3) immobilization of the "ferrocenylated" protein to the CB[7]-attached SAM on gold. As a proof of concept, the immobilization of ferrocenylated glucose oxidase (FA-GOx) on a CB[7]-anchored gold substrate, and its use as a glucose sensor, were demonstrated. In principle, this approach can be applied to the immobilization of any biomolecules including nucleic acids on any surfaces including glass, silicon, silica, and polymers. The synthetic host−guest pair with exceptional affinity, chemical robustness, simple preparation, and easy handling may replace the biotin−avidin system not only in the immobilization of biomolecules on solid surfaces, but also in other applications such as affinity chromatography and immunoassay.