Biosensor application of screen-printed carbon electrodes modified with nanomaterials and a conducting polymer: Ethanol biosensors based on alcohol dehydrogenase

Commercially available screen-printed carbon electrode (SPCE) has been modified with multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs) and polyneutral red (PNR) film. It was then further modified with alcohol dehydrogenase (ADH) to use in the preparation of a disposable amperometric biosensor for ethanol analysis. The effects of various modifications applied to SPCE on its electrochemical biosensor properties toward ethanol have been investigated by measuring changes in current intensity in amperometric detection of ethanol. These changes were attributed to the changes in conductivity and electrocatalytic activity of the electrodes upon modifications. The biosensor response for ethanol was investigated as a function of pH, working potential, amount of ADH and NAD(+). Optimum values of these parameters in the ethanol determination was found as 7.75 for pH, +0.2 V for working potential, 150 units for the amount of enzyme and 7 mM for the amount of coenzyme. Sensitivity, linear range, limit of detection and limit of quantification of the biosensor were found to be 0.49 mu A.mM(-1), 320.2 mu M - 1000 mu M, 96.1 mu M and 320.2 mu M, respectively. The repeatability of the biosensor was tested at +0.2 V with 400 mu M ethanol solution. The relative standard deviation (RSD) was calculated to be 1.57% (for n =10). The operational stability studies have shown that the initial amperometric response of biosensor to ethanol decreased by 72.2% at the 7th day. Storage life studies have shown that the sensitivity of the biosensor decreased by 78.3% at the end of sixth week. The developed biosensor has been tested for ethanol determination in commercial alcoholic beverages. The results were in good agreement with those certified by the suppliers. The developed ethanol biosensor is promising to be used for ethanol analysis in real samples as simple, practical and disposable device without requiring laborious sample pre-treatment producers. (C) 2016 Elsevier B.V. All rights reserved.