Biomimetic silication of surfaces and its application to preventing leaching of electrostatically immobilized enzymes

Biomimetic condensation of silicic acid onto a polyethyleneimine (PEI) coated surface was investigated using quartz crystal microbalance measurements (QCM). It was shown that precipitation of silicic acid proceeds in two sequential stages. Very fast PEI-assisted silica formation is followed by slow non-specific gel deposition. Electrostatic adsorption of enzyme and precipitation of silicic acid on the surface of PEI-modified screen-printed carbon electrodes (SPCE) were found to be competing and therefore silica formation does not increase enzyme load. However, incubation of the PEI-modified surface in silicic after immobilization of enzyme can be used to solidify and reinforce the PEI backbone via non-covalent concreting by silica. This simple and quick procedure ultimately stabilizes electrostatically immobilized enzymes against washing-off in low pH and/or ionic strength environments.