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.

► Mannosylated polyaniline was synthesized as new sensory materials .
► Mechanisms of Con A binding with mannosylated polyaniline was characterized
► Proton exchange in polyaniline functionalities during binding events was confirmed.
► Carbohydrate impedance sensor shows excellent analytical merits.
► Glycosylated polyaniline opens the way for new label free carbohydrate biosensors.