Analysis And Detection Of D-Alanine And Organophosphorus Pesticides

Amino acids are commonly found in nature in the form of L-isomers,while D-isomers are common components of bacterial cell wall.D-amino acids（DAAs）in food are generally caused by some extreme conditions in the process of food production,such as high temperature,extreme solvent p H,microbial pollution,etc.DAAs is not easy to be absorbed directly by human body,and its abnormal content in human body has been proved to be related to a variety of different diseases,among which D-alanine（D-Ala）has been proved to be specifically related to early gastric cancer.At the same time,organophosphorus pesticides（OPs）have been widely used in agricultural production because of their high insecticidal efficiency and the ability to effectively improve crop yield.However,most organophosphorus pesticides are highly toxic.Excessive or improper use will not only pollute the environment,but also cause harm to human health,and even lead to death.Therefore,rapid and sensitive detection of D-Ala and OPs is of great significance for early clinical diagnosis and environmental protection.Among the various detection methods,most of the traditional detection methods are more complicated,and the sample pretreatment process is time-consuming.Biosensor detection method overcomes these shortcomings,has the advantages of simple operation,rapid detection,specific recognition of target,high sensitivity,and can be used for the detection of target content in vivo.In this paper,two different biosensors were constructed for the quantitative detection of D-Ala and OPs.The main contents of this paper are as follows:（1）A label free and highly sensitive fluorescent biosensor was developed for the quantitative detection of D-Ala based on manganese dioxide（Mn O₂）nanosheets and cationic polymer（PFP）.Due to the fluorescence internal filtration effect（IFE）,the fluorescence of PFP was absorbed by Mn O₂ nanoplates,which led to the quenching of the fluorescence signal.In the presence of D-Ala and D-α-amino oxidase（DAAO）,DAAO specifically oxidizes D-Ala to produce hydrogen peroxide（H₂O₂）,which decomposes Mn O₂ nanosheets to restore the fluorescence of PFP.Based on this,a method for detecting D-Ala is designed,which is expected to be used in the early diagnosis of cancer.The linear range of the method is 1.0 n M～1.0 m M,and the detection limit is 0.35 n M.The results showed that the accuracy of the method was98%～109%.The standard deviation is 2.31%～6.2%.（2）We synthesized an easily prepared N-（4-aminobutyl）-N-ethyl isoluminol/cobalt ion/chitosan(ABEI/Co²⁺/CS)hydrogel material,and chose metal organic frameworks（MOF-Pt）as a catalyst to build a glow type chemiluminescence（CL）imaging sensor for OPs and D-Ala detection.Hydrogen peroxide（H₂O₂）was synthesized from acetylcholine chloride（ATCh）under the catalysis of acetylcholinesterase（ACh E）and choline oxidase（CHO）.H₂O₂ participated in luminol system to produce chemiluminescence signal.The presence of OPS can inhibit the activity of ache,reduce the formation of H₂O₂ in the system,and reduce the signal intensity of chemiluminescence.The linear range of chlorpyrifos was 0.50 ng/m L～1.0μg/m L,the detection limit was 0.21 ng/m L,and 17 organophosphorus pesticides could be detected simultaneously.On the other hand,D-α-amino oxidase（DAAO）catalyzes the oxidation of D-Ala to produce H₂O₂,which participates in the chemiluminescence of luminol system.Therefore,the sensor can also be used to detect D-Ala in serum,and its detection limit is 0.12μM.Therefore,the sensor has broad application prospects not only in food safety,but also in clinical diagnosis.