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 (131)1)) 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 131)1) surface. A 131)1) interface with 60% surface-bound mannose showed a detection limit of similar to 5 +/- 0.5 nM for Lens culinaris lectin, with an affinity constant of K-Lambda = (2.63 +/- 0.5) x 10(6) M-1.