New Methods For The Detection Of 5-hydroxymethylfurfural And Monoamine Oxidases B

In the modern food industry,different food processing technologies are used to extend the shelf life of food and improve the color,aroma and taste of food to meet sensory needs.However,the associated hazards of food processing have a great impact on the flavor and quality of food,and even cause certain harm to human health.Among them,5-hydroxymethylfurfural（HMF）is a potentially risky substance produced by Maillard reaction and caramelization reaction of sugary foods during thermal processing or storage.It can be used as an index to measure the freshness of food.Nevertheless,high concentrations of HMF have certain cytotoxicity and neurotoxicity,and excessive intake can irritate mucous membranes such as eyes,skin,and upper respiratory tract.In addition,HMF can be converted into carcinogenic compound 5-sulfaoxymethylfurfural（SMF）after entering the body,which in turn induces a series of diseases.On the other hand,when cells are subjected to oxidative stress,they will lose their normal viability and trigger a variety of cell reactions through the production of secondary reaction species,eventually leading to cell death.Moreover,the human central nervous system is particularly vulnerable to oxidative stress due to its high oxygen demand and high concentration of lipid peroxide.Monoamine oxidase B（MAO-B）,as one of the important enzymes to maintain the steady-state balance of neurotransmitters and other biogenic amines in cells,actively participates in the regulation of monoamine neurotransmitters and oxidative stress in human body.However,when MAO-B is over activated,it will increase the level of intracellular ROS,lead to oxidative stress,and ultimately accelerate the development of neurodegenerative diseases.Therefore,HMF and MAO-B are related to food safety and neurodegenerative diseases respectively,which are both research hotspots closely related to human health.It is particularly important to construct their related detection methods.In this paper,two biosensors were constructed to detect the HMF and MAO-B respectively.The main contents of this paper are as follows:（1）Based on strand displacement reaction and magnetic separation,a ratiometric fluorescence sensor was constructed to detect HMF with the help of Mn O₂ nanosheets.Amino-functionalized magnetic beads（NH₂-MBs）used in magnetic separation can recognize the target HMF and aldehyde-functionalized DNA（S0-CHO）through aldehyde amine condensation reaction.The S0-CHO and HMF competed for binding to NH₂-MBs.Then,S0-CHO was collected from supernatant by magnetic separation.In the presence of HMF,the obtained S0-CHO induced the formation of T-shaped DNA by strand displacement reaction,lighting the fluorescence of FAM.In the absence of HMF,no S0-CHO was present to ignite T-shaped DNA.In this situation,fluorescence of Cy5 was turned on.The sensor has a wide linear range from 5 n M to 5μM.The use of fluorescence intensity ratio can reduce the generation of false positive signals and improve the specificity and sensitivity of the detection method.This method can be applied to detect the content of HMF in different foods.（2）Based on localized surface plasmon resonance induced by silver deposited Au NS,a nanosensor was constructed sensitive detection of MAO-B.Benzylamine was selected as a specific substrate of MAO-B,the enzyme product benzaldehyde will react with Tollens’reagents to deposit sliver on the surface of Au NS in situ and lead to the change of the morphology of Au NS,resulting in the change of LSPR peak blue-shift,visible color and the scattering color.In the colorimetric analysis mode,the constructed sensor showed a good linear relationship in the range of 0.01～1μg/m L.Then single-particle scattering strategy was applied to improve the detection sensitivity.In the dark field analysis mode,there is a good linear relationship between LSPR peak shift and MAO-B concentration range from 0.5 to 20 ng/m L,which was much more sensitive than the UV method and the previously reported methods.Since Au NS plasmonic probes without additional modification and labeling,such a straight,simple and sensitive single particle plasmonic imaging strategy exhibits promising potential in the field of biosensing and clinical diagnosis of diseases.