Impact Research of Physical-Chemical Factors on the Activity of Modified Enzyme Electrodes

To modify graphite electrodes with a conductive enzyme polymer matrix, the method of drip application of a liquid polymer solution of various compositions was used: polyvinylpyrrolidone (40%), chitosan (0.1%), glutaric dialdehyde (0.1%), glucoxidase and peroxidase in a ratio of 2:5. To assess the effect of the immobilization time (x1), the pH of immobilization (x2) and the enzyme/carrier ratio (x3) on the activity of the enzyme electrodes, a three-factor and three-level Box-Benken and RSM design was used. This model was able to adequately predict the results of immobilization within the range of variables used. The most favorable conditions and the largest number of molecules of the enzyme complex are in the electrochemically active state when they are immobilized on PVP using modifying agents chitosan and glutaraldehyde. The results demonstrate that the productivity of the enzymatic biofuel element is directly proportional to the activity of the immobilized GOX/HRP complex, since in this case the glucose oxidation reaction can proceed more efficiently.

Fully Inkjet-Printed Biosensors Fabricated with a Highly Stable Ink Based on Carbon Nanotubes and Enzyme-Functionalized Nanoparticles

Enzyme inks can be inkjet printed to fabricate enzymatic biosensors. However, inks containing enzymes present a low shelf life because enzymes in suspension rapidly lose their catalytic activity. Other major problems of printing these inks are the non-specific adsorption of enzymes onto the chamber walls and stability loss during printing as a result of thermal and/or mechanical stress. It is well known that the catalytic activity can be preserved for significantly longer periods of time and to harsher operational conditions when enzymes are immobilized onto adequate surfaces. Therefore, in this work, horseradish peroxidase was covalently immobilized onto silica nanoparticles. Then, the nanoparticles were mixed into an aqueous ink containing single walled carbon nanotubes. Electrodes printed with this specially formulated ink were characterized, and enzyme electrodes were printed. To test the performance of the enzyme electrodes, a complete amperometric hydrogen peroxide biosensor was fabricated by inkjet printing. The electrochemical response of the printed electrodes was evaluated by cyclic voltammetry in solutions containing redox species, such as hexacyanoferrate (III/II) ions or hydroquinone. The response of the enzyme electrodes was studied for the amperometric determination of hydrogen peroxide. Three months after the ink preparation, the printed enzyme electrodes were found to still exhibit similar sensitivity, demonstrating that catalytic activity is preserved in the proposed ink. Thus, enzyme electrodes can be successfully printed employing highly stable formulation using nanoparticles as carriers.