Carbohydrate-Mediated Biomolecular Recognition and Gating of Synthetic Ion Channels

Nanochannel-based biosensing devices have been proposed for selective detection of protein analyte molecules. However, the design and miniaturization of reusable channel-based biosensors is still a challenge in nanoscience and biotechnology. We present here a reusable nanofluidic biosensor based on reversible lectin-carbohydrate interactions. The nanochannels are fabricated in heavy ion tracked polymer membranes. The channel walls are functionalized with p-aminophenyl alpha-D-mannopyranoside (APMP) monolayers through carbodiimide coupling chemistry. The chemical (mannopyranoside) groups on the inner channel walls serve as binding sites and interact with specific protein molecules. The binding (bioconjugation)/unbinding of proteins inside the confined geometry gives measurable changes in the electrical conductance for the case of single channel and in the permeation rate for a multichannel membrane. The modified-channel selectively recognizes concanavalin A (ConA) protein, but not the control proteins (lysozyme and bovine serum albumin), because ConA specifically binds with the mannopyranoside moieties. The method permits ConA detection in the range 10 nM to 1000 nM. Moreover, the ConA binding/unbinding is reversible, allowing several measuring cycles by washing the bioconjugated-channels with mannose solution. The experimental results are explained qualitatively by introducing a phenomenological model that incorporates the basic experimental trends observed in the current-voltage curves.