Vanadium PentoxideNanobelts for Lactose Oxidase-Likeand Peroxidase-Like Cascade Reactions for Colorimetric Detection ofLactose in Milk

Lactose serves as a crucial biomarker for assessing the quality and safety of milk. Therefore, the precise measurement of the lactose content is of paramount importance. Herein, we demonstrate that vanadium pentoxide (V₂O₅) nanobelts exhibit lactose oxidase-like activity. Additionally, a colorimetric biosensor for lactose detection was developed by leveraging a cascade reaction mechanism of V₂O₅ nanobelts possessing lactose oxidase-like and peroxidase-like activities. The sensor shows a linear response from 0.1 to 1.0 mM lactose, with a detection limit of 0.04 mM, and demonstrates accuracy and reliability in milk analysis. The accuracy of the proposed colorimetric method was verified by capillary electrophoresis in five milk samples. A self-designed portable device incorporating this technology serves to enhance its potential for practical application, enabling the precise and convenient detection of lactose levels in milk. This development not only simplifies the measurement process but also broadens the scope of its use in various settings, including on-site testing and quality control.