Electrical communication between a water-soluble 1,1′-dimethylferrocene-2-hydroxypropyl-β-cyclodextrin complex and glucose oxidase: biosensor applications

2-Hydroxypropyl-β-cyclodextrin (HPBC) was used to enclose 1,1′-dimethylferrocene (DMF) into its hydrophobic cavity to form a yellow water-soluble complex with a molar ratio of about 6 to 1. The cyclic voltammogram of the complex solution exhibited one single electron transfer process with a half-wave potential of 170 mV. The oxidation potential of the DMF-HPBC complex was not affected by pH ranging from pH 4·7 to 8·8 and the difference between the anodic and cathodic peak potentials was observed to be 95 mV. The DMF-HPBC complex was used together with immobilized glucose oxidase to construct a mediated biosensor for the determination of β-D-glucose. The enzyme was either convalently immobilized on a preactivated Immunodyne nylon membrane or retained onto the sensing area of the electrode by a dialysis membrane. In the latter preparation, the enzyme electrode exhibited a detection limit of 0·02 mM and a linear range of 0·02 to 0·5 mM. About 2 min was required to attain 90% of full response. The biosensor was effective for the determination of glucose in food and beverage samples.