Cellulose-based biosensors exploiting diamine-oxidase and soybean peroxidase for biogenic amine determination in solution

Two biosensors with enzymes immobilized on fibrous cellulose powder and paper have been developed for the colorimetric detection of biogenic amines, which are of great interest for food and health security. These systems exploited diamine oxidase (DAO) and soybean peroxidase (SBP) catalytic activities. DAO oxidizes the amines, producing ammonia and hydrogen peroxide; the latter activates SBP, catalyzing the oxidation of the co-substrates with the formation of a purple product, easily detectable by UV–visible spectrometry. For most of the examined amines, the quantification resulted in being fast and effective even at low concentrations, reaching calculated Limits Of Detection (LOD) between 10−6-10−8 M. However, proper methodological adjustments were needed for catecholamines, implying the exclusive use of SBP-based materials. Biosensors' characterizations showed the rise of peculiar phenomena during their preparation: paper underwent hydrophobization and shrinkage after the oxidation step, while DAO caused unexpected fiber thinning in paper and fibers’ coalescence of powdery cellulose. Moreover, infrared spectroscopy and calorimetry demonstrated modifications in hydrogen networks after cellulose and paper treatments. Overall, these changes did not affect the potential of biosensors, which are sensitive, portable, and biodegradable, although there is room for improvement in lowering catecholamine LOD and broadening their promising applicability by testing real matrices.