Paper-based electrochemical biosensor for lactose monitoring

• Autor(a) principal: Santos, Ricardo Jorge Sousa
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/153465
• topic: Lactose; glucose; electrochemistry; laser induced graphene; biosensor; paper; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Dairy products are between one of the most consumed products across the world, however, their consumption is today nearly impossible for around 65% of the world's population, since they possess some kind of intolerance to lactose (one of the main sugars present in these products). As a solution, lactose-free products are often consumed, with the hydrolysis of lactose by lactase, inhibiting the effects attached to lactose consumption. Since these commodities must meet a limit of 0.1% (w/w) of lactose, it has become more important than ever to develop accurate measuring systems that can correctly determine lactose percentage in milk samples. Several methods are used to perform this kind of measurements, however they are in general very expensive and complex, so there is a space in this competitive industry to develop simple, low-cost, and sustainable measuring systems. The reaction between lactase and lactose results in the hydrolysis of lactose, but it also results in the production of glucose and galactose. Glucose, specifically, produces an electrochemical response when reacting with glucose oxidase, producing H2O2 in the process. This molecule, when interacting with a substance like Prussian blue (PB) also produces an electrochemical signal that can be measured by a potentiostat. With that in mind, a biosensor composed of two enzymes and PB was developed to measure lactose in milk. A pre-treated paper substrate, together with a laser induced graphene-based pattern was used, therefore meeting the sustainability goals of this work. The sensor, with 5 mM of glucose oxidase, 100 mM of lactase and 5 mM of PB was able to correctly measure current produced by the milk samples for different concentrations of lactose, presenting a significative difference in current density (442.36 μA/cm2) between semi-skimmed milk and lactose-free semi-skimmed milk.