Characterization of different diamond-like carbon electrodes for biosensor design

Diamond-like carbon (DLC) films are gaining big interest in electrochemistry research area. DLC electrodes made with different ratio of sp3/sp2 carbon hybridization or doped with different percentages of nickel were characterized electrochemically by cyclic voltammetry and by amperometric measurements towards hydrogen peroxide. SiCAr1 and SiCNi5% were chosen as sensitive transducers for the elaboration of amperometric glucose biosensors. Immobilization of glucose oxidase was carried out by cross-linking with glutaraldehyde. Measurements were made at a fixed potential + 1.0 V in 40 mM phosphate buffer pH 7.4. SiCAr1 seems to be more sensitive for glucose, 0.6875 μA/mM, than SiCNi5%, 0.3654 μA/mM. Detections limits were 20 μM and 30 μM, respectively. Apparent Michaelis-Menten constants were found around 3 mM. Forty-eight percent and 79% of the original response for 0.5 mM glucose remained after 10 days for both biosensors, respectively.