Development of amperometric α-ketoglutarate biosensor based on ruthenium–rhodium modified carbon fiber enzyme microelectrode

A rapid and highly sensitive miniaturized amperometric biosensor for the detection of α-ketoglutarate (α-KG) based on a carbon fiber electrode (CFE) is presented. The biosensor is constructed by immobilizing the enzyme, glutamate dehydrogenase (GLUD) on the surface of single carbon fiber modified by co-deposition of ruthenium (Ru) and rhodium (Rh) nanoparticles. SEM and EDX shed useful insights into the morphology and composition of the modified microelectrode. The mixed Ru/Rh coating offers a greatly enhanced electrocatalytic activity towards the detection of β-nicotinamide adenine dinucleotide (NADH), with a substantial decrease in overpotential of ∼400 mV compared to the unmodified CFE. It also imparts higher stability with minimal surface fouling, common to NADH oxidation. Further modification with the enzyme, GLUD leads to effective amperometric biosensing of α-KG through monitoring of the NADH consumption. A very rapid response to dynamic changes in the α-KG concentrations is observed with a response time of 6 s. The current response is linear between 100 and 600 μM with a sensitivity of 42 μA M−1 and a detection limit of 20 μM. This proof of concept study indicates that the GLUD-Ru/Rh-CFE biosensor holds great promise for real-time electrochemical measurements of α-KG.