High-performance amperometric biosensor for flow injection analysis consisting of a replaceable lactate oxidase-based mini-reactor and a silver amalgam screen-printed electrode

Abstract

L-lactic acid (LA) is an essential compound in the winemaking process; furthermore, it is considered a significant biomarker for the diagnosis of a wide range of diseases, including cancer. Therefore, a cost-effective and reliable biosensing system for FIA is developed here for rapid and selective determination of LA. The biosensor architecture includes an easily replaceable lactate oxidase (LOx)-based mini-reactor connected in front of a silver amalgam screen-printed electrode acting as a transducer. The mini-reactor represents a tube filled with mesoporous silica powder (SBA−15) coated with covalently immobilized LOx. The principle of LA determination is based on the amperometric monitoring of oxygen consumption by its four-electron reduction at −900 mV vs. Ag pseudo-reference electrode, which avoids the interferences from commonly interfering compounds. The application of a strategy of a spatially separated biorecognition and detection part allowed for the immobilization of a notably large amount of enzyme (one mini-reactor contains c.a. 270 μg of the LOx), which, in turn, ensured excellent operational (93.8% of the initial signal after 350 measurements) and storage (96.9% of the initial biosensor response after 7 months) stability. The newly developed high-performance biosensor was successfully tested for the quantification of LA in saliva, wine, and dairy products.