Two-enzyme lactose biosensor based on β-galactosidase and glucose oxidase deposited by AC-electrophoresis: Characteristics and performance for lactose determination in milk

In this paper, we have investigated the deposition of two enzymes β-galactosidase (β-Gal) and glucose oxidase (GOx) using alternating current electrophoretic deposition (AC-EPD) to manufacture a lactose sensor. Using the optimal deposition parameters and optimal testing conditions, the sensor has a sensitivity up to 111 nA/mM mm2. This sensitivity is high considering the low activity of the enzymes employed in this study (9 units/mg for β-Gal and 5.6 units/mg for GOx). The sensor has a large linear range up to 14 mM lactose, fast response time (∼8 s) and reasonable stability without employing any stabilizers or outer polymer membrane. In addition, it is easy and simple to manufacture, highly reproducible and cheap because low activity enzymes are used. The sensor was tested to determine lactose in milk samples and is demonstrated to be accurate.