New fructose biosensors utilizing a polypyrrole film and d-fructose 5-dehydrogenase immobilized by different processes Original Research Article

Two amperometric biosensors for fructose detection were developed by immobilizing d-fructose 5-dehydrogenase by two different immobilization processes. For the first biosensor, the occlusion enzymatic immobilization technique was employed, the enzyme being immobilized in a polypyrrole (PPY) film, over a platinum electrode containing sodium ferricyanide as mediator. With this sensor, about 100 analyses were performed over a period of 1 week with daily use. The second was constructed using the crosslinked covalent bond method, the enzyme being immobilized onto a PPY film doped with hexacyanoferrate supported on a platinum electrode surface. This biosensor was used for, approximately, 200 analyses in 2 weeks of continuous use. Analytical parameters, such as pH, ionic strength, interferences and response time of both sensors were also studied. The biosensors were utilized for fructose determinations in three different samples of dietetic products and presented a good correlation with the standard colorimetric method. A linear response range to both biosensors was 0.1–0.8 mmol l−1 fructose with a r.s.d. of 0.68%.