Surface molecular imprints of WGA lectin as artificial receptors for mass-sensitive binding studies

Wheat germ agglutinin (WGA) lectin is a model compound for the interaction between viruses and cells during infection events and thus an interesting analyte for mass-sensitive sensing to study these interaction phenomena. Scanning tunneling microscopy studies reveal that surface molecular imprinting leads to cavities having the dimensions of WGA dimers. These reincorporate WGA from phosphate-buffered saline between 1 and 160 mu g/ml. Whereas the quartz crystal microbalance (QCM) frequency for molecularly imprinted polymer (MIP)-coated electrodes decreases, indicating uptake of the analyte, their nonimprinted counterparts yield positive, concentration-dependent frequency shifts characteristic for slip of the analyte on the QCM surface. The MIPs achieve selectivity factors towards bovine serum albumin of roughly 4 at higher protein concentrations. Brunauer-Emmett-Teller analysis reveals that binding is favored by 29 kJ/mol until the adsorption of up to ten monolayers on the MIP, whereas above this range the value is lower. Together with the binding behavior of MIP and nonimprinted polymers, this indicates that the MIP acts as a nucleus for multilayer deposition onto the surface.