Amperometric Detection of Lactose Using beta-Galactosidase Immobilized in Layer-by-Layer Films

Author(s)

Campos, Paula P. ^[1] ; Moraes, Marli L. ^[2] ; Volpati, Diogo ^[3] ; Miranda, Paulo B. ^[3] ; Oliveira, Jr., Osvaldo N. ^[3] ; Ferreira, Marystela ^[1]

Affiliation

^[1] Univ Fed Sao Carlos, UFSCar, BR-18052780 Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Paulo, Inst Ciencia & Tecnol, Unifesp, BR-12231280 Sao Jose Dos Campos, SP - Brazil

^[3] Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 6, n. 14, p. 11657-11664, JUL 23 2014.
• Web of Science Citations: 21

Abstract

A direct, low-cost method to determine the concentration of lactose is an important goal with possible impact in various types of industry. In this study, a biosensor is reported that exploits the specific interaction between lactose and the enzyme beta-galactosidase (beta-Gal) normally employed to process lactose into glucose and galactose for lactose-intolerant people. The biosensor was made with beta-Gal immobilized in layer-by-layer (LbL) films with the polyelectrolyte poly(ethylene imine) (PEI) and poly(vinyl sufonate) (PVS) on an indium tin oxide (ITO) electrode modified with a layer of Prussian Blue (PB). With an ITO/PB/(PEI/PVS)(1)(PEI/beta-Gal)(30) architecture, lactose could be determined with an amperometric method with sensitivity of 0.31 mu A mmol(-1) cm(-2) and detection limit of 1.13 mmol L-1, which is sufficient for detecting lactose in milk and for clinical exams. Detection occurred via a cascade reaction involving glucose oxidase titrated as electrolytic solution in the electrochemical cell, while PB allowed for operation at 0.0 V versus saturated calomel electrode, thus avoiding effects from interfering species. Sum-frequency generation spectroscopy data for the interface between the LbL film and a buffer containing lactose indicated that beta-Gal lost order, which is the first demonstration of structural effects induced by the molecular recognition interaction with lactose. (AU)

• FAPESP's process: 12/16158-0 - Nanostructured films inorganic-organic hybrids for environmental sensors
• Grantee: Marystela Ferreira
• Support Opportunities: Regular Research Grants