Fabrication Of Metal-Organic Frameworks-based Electrochemical Sensor And Its Application In Detection Of Aquatic Product Freshness

Fishery resources are important part of natural resources.Aquatic products;which are rich in high-quality protein,unsaturated fatty acids,necessary macro and micro nutrients such as omega-3 fatty acids,vitamins and minerals,are an important part of our diet.In comparison to other meats,aquatic products have abundant endogenous enzymes and psychrophilic microorganisms which resulted in quality deterioration and loss in nutrition during long period of sea transportation after fishing.These might endanger consumers health.Most of the current detection methods for aquatic product freshness involved the use of high-end precision equipment.Although the detection results are accurate,it is often time consuming.Therefore,it is of great significance to the modern food industry to develop a new method for quick and sensitive detection of fish freshness.Present work has fabricated two electrochemical sensors for detection of seafood freshness.Firstly,Cu-MOF nanofibers were synthesized through hydrothermal synthesis by incorporating non-conductive MOF precursor material into a copper-based conductive nanofiber matrix.The synthesized Cu-MOF exhibits good electrochemical behavior,excellent chemical and thermal stability,and high porosity and surface area.Cu-MOF is then mixed with sodium alginate to form a stable nanofiber membrane.Xanthine oxidase(XOD)is mixed into this biocompatible copper-based MOF membrane to effectively encapsulate XOD on the surface of glass carbon electrode(GCE).Results showed that the constructed biosensor has good electron transfer performance,good reusability(100 repeated tests),excellent storage stability(up to 20 days)for detection of hypoxanthine and xanthine.The fabricated enzyme electrochemical sensor has high sensitivity,low detection limit,wide linear detection range(0.01 to 10 ?M for both hypoxanthine and xanthine)and can be used to evaluate the freshness of chilled aquatic product.Secondly,we synthesized another metal-organic framework(Zn-MOF)with xanthine oxidase-like activity by hydrothermal synthesis.By entrapping Zn-MOF with sodium alginate on the GCE electrode,an enzyme-free electrochemical detection platform was successfully constructed.Results showed Zn-MOF is a good material with XOD like catalyze behavior which can degrade of hypoxanthine and xanthine(Km=0.082 m M,37?).The fabricated electrochemical sensor has good reusability(100 tests),excellent storage stability(up to 42 days),high sensitivity,low detection limit and wide linear detection range(0.01 to 500 ?M for xanthine and 0.05 to 1000?M for hypoxanthine).The fabricated sensor has a recovery rate of 86±1? 109±1% and 98±1?113±1% when used for detection of xanthine and hypoxanthine in four different fishes.This electrochemical sensor provides a new and effective method for the detection of fish freshness.