1. The carbon substrates were coated with lysozyme by soaking them in a lysozyme solution and then washing off the excess lysozyme using a phosphate buffer solution.
2. A homogeneous GOx/CNT suspension was prepared by mixing CNTs and then GOx into a phosphate buffer solution, all the while sonicating the mixture.
3. A silica-precipitation reaction mixture was made by combining a phosphate buffer solution and a solution of tetramethyl orthosilicate in dilute hydrochloric acid.
4. The GOx/CNT suspension was incorporated into the silica-precipitation reaction mixture.
5. The lysozyme-coated carbon substrates were exposed to the reaction mixture at room temperature, allowing enough time (30 min.) for the formation of silica via precipitation catalyzed by the lysozyme.
6. The resulting composite-coated carbon substrates were washed with water, then dried.

The chemical compositions of the coatings were analyzed by use of x-ray photo-electron spectroscopy. Geometric aspects of the composite nanostructures were analyzed by use of scanning electron microscopy. Electrochemical properties were analyzed by use of cyclic voltammetry. The figure presents an example of plots of cyclic voltammetric scans made in the presence and absence of glucose, showing stable oxidation and reduction peaks at an optimal potential close to that of the FAD/FADH2 cofactor of immobilized glucose oxidase. [FAD/FADH2" refers to flavin adenine dinucleotide (FAD), a coenzyme that is derived from riboflavin and that becomes FADH2 as it accepts a pair of high energy electrons]. The immobilized GOx was found to be stable for a period of one month and to retain catalytic activity toward the oxidation of glucose.

This work was done by Heather R. Luckarift and Glenn R. Johnson of the Air Force Research Laboratory and Dmitri Invitski, Kateryna Artyuskova, Rosalba A. Rincón, and Plamen Atanassov of the University of New Mexico.

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