A biosensor design involving coimmobilization of
fructose dehydrogenase (FDH) and
inulinase (INU) on a
gold nanoparticle-
cysteamine (
Cyst) self-assembled monolayer (SAM)-modified
gold electrode (Au(coll)-
Cyst-AuE), for the determination of the
carbohydrate inulin in foodstuffs, is reported.
Tetrathiafulvalene (TTF), used as the mediator, was also coimmobilized by crosslinking with
glutaraldehyde. INU catalyzes the hydrolysis of
inulin, forming
fructose that is detected through the
fructose dehydrogenase system by the electrochemical oxidation of TTF at the bioelectrode. The variables involved in the preparation and performance of both the single
enzyme FDH biosensor and the bienzyme
inulin biosensor were optimized. The FDH-Au(coll)-
Cyst-AuE biosensor exhibited rapid and sensitive response to
fructose, allowing the obtention of improved analytical characteristics for the determination of
fructose with respect to other FDH electrochemical biosensors. Moreover, the lifetime of this biosensor was 35 days. The bienzyme INU/FDH-Au(coll)-
Cyst-AuE biosensor provided a calibration plot for
inulin in the (5-100)x10(-6) M linear range, with a detection limit of 6.6 x 10(-7) mol L(-1). One single bienzyme biosensor responded within the control limits, set at +/-3x the standard deviation of the currents measured on the first day of use, for more than 5 months. Furthermore, the biosensor exhibited high selectivity with respect to other
carbohydrates. The usefulness of the biosensor was evaluated by the rapid determination of
inulin in food products involving minimization of the
fructose interference.