Glycosylated aniline polymer sensor: amine to imine conversion on protein-carbohydrate binding

In this report, functionalized mannosylated aniline polymer (manno-PANI) was investigated as an electrochemical platform to study carbohydrate-protein interactions by exploiting the conductivity change of manno-PANI when the specific lectin binding occurs. A systematic study was performed to characterize the interconversion of polyaniline content (from amine to imine) in manno-PANI by UV-vis spectroscopy during its binding with concanavalin A (Con A). Both X-ray photoelectron spectrometry (XPS) and UV-vis results suggest that Con A binding with the manno-PANI film triggers the switching of amine functionalities in the polyaniline backbone, converting them to imine forms. Electrochemical impedance spectroscopy (EIS) was used to quantify the specific interactions between Con A and mannose by measuring the impedance change of manno-PANI film for the detection of Con A. A linear relationship between the impedance and Con A concentration was obtained, and the detection limit reaches to 0.12 nM Con A in a buffer solution (pH=7.4), whereas the addition of nonspecific control lectins to the same manno-PANI film gave very little impedance variations. Stability characterization of the manno-PANI film over 20 weeks shows a maximum drift of only 3% from the original signal. Thus, the uniquely constructed carbohydrate-PANI hybrid is a promising new carbohydrate recognition moiety for studying carbohydrate-protein interactions, presumably leading to a new electrochemical method for characterization of carbohydrate-protein interactions and carbohydrate-mediated intercellular recognitions.