Abstract
Histamine, an important safety index for aquatic products, can also be used as a freshness indicator for red-fleshed fish. In this work, magnetic graphene oxide (Fe3O4@GO, MGO) was applied to immobilize diamine oxidase (DAO) through a method of adsorption and covalent bonding. Under the optimized conditions, magnetic DAO prepared by adsorption immobilization had a higher enzyme activity than that of free enzyme, which was selected for the sensor construction. A colorimetric biosensor based on magnetic DAO induced etching of gold nanorods (AuNRs) was developed for the detection of histamine in fish. The developed biosensor showed an excellent response toward histamine with a low detection limit of 1.23 μM and had negligible interference from other diamines. With increasing the histamine concentration, the AuNRs after the reaction exhibited colors ranging from dark green to blue-green, blue, purple, red, and colorless. The etching induced multicolor change of AuNRs indicated the presence of different contents of histamine in mackerel during storage, and was consistent with the overall change in the content of the total volatile basic nitrogen (TVB-N). Thus, it was indicated that the proposed colorimetric biosensor with a naked-eye-detectable readout has a great potential to evaluate the freshness of red-fleshed fish high in histamine.
Highlights
Histamine is a kind of biological amine produced from histidine under the action of histidine decarboxylase after the death of a fish
The covalent bonding method activates the -COOH group of MGO through Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/NHS, and the -COOH group combines with the -NH2 group of diamine oxidase (DAO) to form a covalent bond and immobilize on the MGO [27]
A colorimetric biosensor for fish freshness based on histamine content was proposed using magnetic DAO as a biosensing element and etched AuNRs as signal converters
Summary
Histamine is a kind of biological amine produced from histidine under the action of histidine decarboxylase after the death of a fish. It is the most abundant and main biogenic amine in red-fleshed fish mainly belonging to the family Scombridae, such as mackerel and tuna [1]. Histamine is an important biomarker for food spoilage and can be used as a freshness index in this kind of fish [2,3]. The establishment of a fast, simple, and sensitive detection method for histamine that can effectively evaluate the freshness of red-fleshed fish has important practical significance and is challenging
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