Simultaneous monitoring of glucose, lactate and L-glutamate in rat blood by a flow-injection enzyme electrode array system

Rapid measurement of glucose, lactate and L-glutamate level in blood is important for studying the balance of energy in body. The flow-injection analysis (FIA) system with enzyme electrode array was based on neutral red-doped silica (NRDS) nanoparticles as electrocatalyst. These uniform NRDS nanoparticles (about 50 ± 3 nm) were prepared by a water-in-oil (W/O) microemulsion method, and characterized by TEM technique. The doped inside neutral red maintained its high electron-activity, while the outside nano silica surface prevented neutral red from leaching out into the aqueous solutions and showed high biocompability. These nanoparticles were then mixed with the glucose oxidase (GOD), lactate oxidase (LOD) or L-glutamate oxidase (L-GLOD), and immobilized on a three carbon-disk electrode (CE) array, respectively. A thin Nafion film was coated on the enzyme layer to prevent interference such as ascorbic acid and uric acid in the blood. The proposed flow-injection analysis with NRDS-enzyme electrode array method enables simultaneously monitoring various levels of glucose, lactate and L-glutamate in blood.