Bi-enzymatic biosensor for on-site, fast and reliable electrochemical detection of relevant D-amino acids in bacterial samples

Abstract

In this work, a bi-enzymatic biosensor allowed the total content of D-amino acids (DAAs) determination in highly relevant matrices involving bacteria. The strategy is based on the unique coimmobilization of D-amino acid oxidase (DAAO) and horseradish peroxidase (HRP) enzymes onto a multi-walled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) modified screen-printed electrode (SPCE). The greater amount of AuNPs deposited and hence the greater loading of both enzymes was observed when they were deposited after the activation of the carboxylated MWCNTs with EDC/Sulfo-NHS chemistry. These platforms provided a fast (300 s) and selective quantification of DAAs with excellent precision (RSD < 5%) and accuracy (Recoveries 100–104%) in bacterial samples. Collectively, the electrochemical bi-enzymatic biosensor become an universal, fast, sensitive and easy-to-use approach to determine total content of DAAs in complex matrices.