Label-free detection of lectins on carbohydrate-modified boron-doped diamond surfaces

This paper describes the label-free detection of carbohydrate-lectin interactions. The sensor consists of a boron-doped diamond (BDD) electrode terminated with alkynyl surface groups, which have been functionalized via the CuACC (copper(I)-catalyzed azide-alkyne cycloaddition) "click" reaction with carbohydrate analogues bearing an azido-terminating arm. In this work, electrochemical impedance spectroscopy (EIS) was used as an effective technique to probe the specific interactions of the surface-bound carbohydrates with their complementary lectin partners, and the response was found to be dependent on the relative density of sugar units immobilized on the BDD surface. A BDD interface with 60% surface-bound mannose showed a detection limit of ∼5 ± 0.5 nM for Lens culinaris lectin, with an affinity constant of K(A) = (2.63 ± 0.5) × 10(6) M(-1).