A comparison between different immobilised glucoseoxidase-based electrodes

Biosensors obtained by immobilising glucose oxidase 'unentrapped' and 'entrapped in liposomes', both with a classical H2O2 amperometric electrode and with screen-printed electrochemical sensor, were compared. Electrode response, linearity range and the influence of some parameters as phospholipid nature, temperature and measurement techniques were investigated. Experimental results showed that, while with the unentrapped enzyme the output current is linear only up to about 4 mM glucose concentration, the linearity range increases up to about 20 mM using enzyme-loaded liposomes; however the low permeability of the lipid bilayer decreases the electrode sensitivity to very low values (200 nA/M for palmitoylolelyl phosphatidylcholine liposomes). The approach with screen-printed sensors showed a better performance and gave biosensors with higher sensitivity (about 14500 nA/mM). A mathematical model, useful to compare the behaviour of the different analytical systems and to design electrodes with the required properties, was also proposed.