Optimization of a reusable sandwich-type amperometric phenol biosensor. Experimental and theoretical outcomes

Abstract

The development of reproducible and stable enzyme-based amperometric biosensors for the analysis of phenolic compounds present in food and plants is still a challenge in electroanalytical chemistry. This study describes the optimization process of a sandwich-type amperometric biosensor for detecting oxidizable phenolic compounds. Enzymatic matrix optimization was carried out via a combinatorial study focusing on sensitivity, linear range, and response time. Repeatability and reproducibility studies show variations of only 3 % and 4 %, respectively. When exposed to catechol solutions, the biosensor has a detection limit of 0.9 µM and its linear behavior involves practically three orders of magnitude. This wide linear range can be explained considering that the consumption of oxygen in the nearest of the biosensor limits the enzymatic reaction. The analyses by Michaelis’ equation might give erroneous results, depending on the concentration of phenolic compounds. The exposition of the proposed biosensor to high concentrations of oxidizable phenols produces large amounts of polyphenols that limit its stability. Accordingly, although the biosensors prepared with a high amount of enzyme will have the highest sensitivity values, the proliferation of polyphenols and oxygen consumption may limit their linear range and stability more rapidly. Thus, the long-term stability of a phenol biosensor should be informed not only considering the number of days after its assembling but also the number of times of use and the concentration of phenols to which it was exposed.