Fructose biosensor based on D-fructose dehydrogenase immobilised on a ferrocene-embedded cellulose acetate membrane

The prevention of ferrocene leakage from an electrode by physical retention of mediator in a cellulose acetate membrane matrix is reported here for the first time. Five types of cellulose acetate membranes were prepared, containing 1.8, 5.3, 8.5, and 20.0% of ferrocene and a membrane containing 1.8% of ferrocene and 0.05% of Nafion (R) in the matrix. All the membranes tested, including a cellulose acetate membrane without ferrocene, were much more resistant to ascorbate interference (12-69 nAmM(-1)) in comparison to an uncovered glassy carbon electrode (1152 nAmM(-1)). With increasing amount of ferrocene in the membrane, a decreasing ability of the membrane to retain mediator was observed. Ferrocene-embedded membranes were successfully applied in the construction of a fructose biosensor by immobilisation of PQQ-dependent fructose dehydrogenase. A biosensor with a membrane containing 20.0% of ferrocene in the matrix exhibited the lowest detection limit (3 muM), the shortest response time (45 s) and the highest sensitivity (232 nA mM(-1)). However, this biosensor was unstable because of ferrocene leaching and after 9 h of continuous use only 15% of the initial activity was observed. The biosensor with a cellulose acetate membrane containing 1.8% of ferrocene and 0.05% of Nafion (R) had better stability characteristics, and retained almost 40% of the initial response after 8 h of continuous use, with similar sensitivity (226 nA mM(-1)) and response time (75 s). (C) 2001 Elsevier Science B.V. All rights reserved.