Differential thick-film amperometric glucose sensor with an enzyme-immobilized nitrocellulose membrane

A disposable glucose sensor based on a differential amperometric measurement is fabricated on activated carbon paste electrodes with the use of a glucose oxidase (GOx)-immobilized nitrocellulose (NC) membrane. Two identical three-electrode cells are screen-printed symmetrically on both faces of a single polyester (PE) substrate. Both electrodes of the two-sided sensor strip are covered with NC membranes incorporating a mediator (K-3[Fe(CN)(6)]), one membrane with GOx and the other with bovine serum albumin (i.e., no GOx): the former serves as a glucose-sensing cell and the other as a reference cell. In the differential measurements between these two cells, the response signals toward various redox species other than glucose cancel out. Prior to placing the NC membranes, the working carbon paste electrodes are pretreated by anodizing them in saturated sodium carbonate at 1.2 V (vs. SCE): the electrochemical reversibility of the mediator is found to be enhanced significantly on such an activated electrode. The analytical performance of the proposed differential glucose sensor strip is demonstrated by measuring glucose values in normal and abnormal serum samples: 5.08 +/- 0.52 (found) vs. 5.10 +/- 0.46 (listed), and 16.56 +/- 1.71 (found) vs. 16.92 +/- 1.72 (listed).