Electron Transfer Properties of Dual Self-Assembled Architectures Based on Specific Recognition and Electrostatic Driving Forces: Its Application To Control Substrate Inhibition in Horseradish Peroxidase-Based Sensors

This work describes the synergistic combination of ionic self-assembly and recognition-directed assembly with the aim of creating highly functional bioelectrochemical interfaces compatible with the supramolecular design of a wide variety of biosensing platforms. A recently synthesized glycopolyelectrolyte constituted of polyallylamine bearing redox-active osmium complexes and glycosidic residues (lactose) is used to create a self-assembled structure with sodium dodecylsulfate. In turn, this supramolecular thin films bearing redox-active and biorecognizable carbohydrate units enable the facile assembly of functional lectins as well as the subsequent docking and "wiring" of glycoenzymes, like horseradish peroxidase (HRP) (an elusive enzyme to immobilize via noncovalent interactions). The assembly of this system was followed by quartz crystal microbalance and grazing-incidence small-angle X-ray scattering (GISAXS) studies confirming that spin-coated ionically self-assembled films exhibit mesostructured architectures according to the formation of self-organized lamellar structures. In-depth characterization of the electrocatalytic properties of the biosupramacromolecular assemblies confirmed the ability of this kind of interfacial architecture to efficiently mediate electron transfer processes between the glycoenzyme and the electrode surface. For instance, our experimental electrochemical evidence clearly shows that tailor-made interfacial configurations of the ionic self-assemblies can prevent the inhibition of the glycoenzyme (typically observed in HRP) leading to bioelectrocatalytic currents up to 0.1 mA cm(-2). The presence of carbohydrate moieties in the ionic domains promotes the biorecognition-driven assembly of lectins adding a new dimension to the capabilities of ionic self-assembly.