An Integrated Amperometric Biosensor for the Determination of Lactose in Milk and Dairy Products

• Published in: Journal of agricultural and food chemistry 2010-06, Vol.58 (12), p.7141-7148
• Main Authors: Conzuelo, F, Gamella, M, Campuzano, S, Ruiz, M.A, Reviejo, A. J, Pingarrón, J. M
• Format: Article
• Language: English
• Subjects: Analytical Methods; Animals; Biological and medical sciences; Biosensing Techniques - methods; Biosensors; Biotechnology; Cattle; Dairy Products - analysis; Food industries; Fundamental and applied biological sciences. Psychology; Lactose - analysis; Limit of Detection; Methods. Procedures. Technologies; Milk - chemistry; Milk and cheese industries. Ice creams; Various methods and equipments
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf101173e

An integrated amperometric biosensor for the determination of lactose is reported. The bioelectrode design is based on the use of a 3-mercaptopropionic acid (MPA) self-assembled monolayer (SAM)-modified gold electrode on which the enzymes β-galactosidase (β-Gal), glucose oxidase (GOD), peroxidase (HRP) and the mediator tetrathiafulvalene (TTF) are coimmobilized by a dialysis membrane. β-Gal catalyzes the hydrolysis of lactose, and the produced glucose is catalytically oxidized to gluconic acid and H2O2, which is reduced in the presence of HRP. This enzyme reaction is mediated by TTF, and the reduction of TTF+ at 0.00 V (vs Ag/AgCl) gives rise to an amperometric signal proportional to the lactose concentration. The biosensor exhibits a good repeatability of the measurement carried out with the same biosensor, a good reproducibility of the responses obtained with different biosensors and a useful lifetime of 28 days. A linear calibration plot was obtained for lactose over the 1.5 × 10−6 to 1.2 × 10−4 M concentration range, with a limit of detection of 4.6 × 10−7 M. The effect of potential interferents (sucrose, lactulose, fructose, arabinose, maltose, galactose, glucose and uric and ascorbic acids) on the biosensor response was evaluated. Furthermore, the bioelectrode exhibits a suitable performance in flow-injection systems in connection with amperometric detection. The developed biosensor was applied to the determination of lactose in milk and other foodstuffs (chocolate, butter, margarine, yogurt, cheese and mayonnaise), and the results obtained were validated by comparison with those provided by using a commercial enzyme test kit.