Investigation On Preparation Of Novel Nano-sensing Materials And Their Detection Of Microcystins In Water

Microcystins（MCs）are a class of bioactive cyclic heptapeptide compounds,mainly produced by microcystis aeruginosa in the blue-green algae bloom,which have a strong hepatocarcinogenic effect and pose a serious threat to the safety of drinking water and human health.With the global climate warming and eutrophication of environmental water,cyanobacteria have erupted,and MCs pollution has become an environmental science problem that all countries face.MCs commonly include MC-LR,MC-RR,MC-LY（L,R,Y respectively represent leucine,arginine,tyrosine）and other types.WHO and China’s GB5749-2006 Sanitary Standard for Drinking Water stipulate that the control standard of MC-LR in drinking water is 1μg·L^-1,which puts forward higher requirements for the quality of source water.At present,the main methods to detect microcystins are high performance liquid chromatography-mass spectrometry（HPLC-MS）and biochemical analysis.However,these methods have the disadvantages of long analysis time or high cost.Therefore,it is of great significance to establish a rapid and simple method for the determination of MCs in water.The main contents are as follows:1 Investigation on a dummy imprinted ratiometric fluorescence sensing analysis for the sensitive detection of microcystins in environmental waterIn this work,metformin was used as a dummy template to build a highly sensitive ratiometric fluorescence sensing platform for the detection of microcystin（MCs）.Metformin can be used as a dummy template for MCs due to its partially similar molecular fragments to MCs that can form a specific recognition site cavity.The molecularly imprinted ratiometric fluorescent nanocomposites（CDs-FITC-SiO₂@MIP）of carbon dots（CDs）combined with fluorescein isothiocyanate（FITC）are synthesized,in which the CDs and FITC serve as assisted response signals and reference enhancement signals,respectively.MCs can simultaneously induce an obvious fluorescence quenching effect for the CDs and a reference fluorescence enhancement for FITC-SiO₂,enabling ratiometric fluorescence detection of MCs.Thus,CDs-FITC-SiO₂@MIP used as a signal probe has favorable sensitivity,stability,and selectivity.More importantly,a good linear relationship between the fluorescence intensity ratio(I_620/450)and the concentration of MCs in the range of 0.5～500μg L^-1is obtained with the detection limit（LOD）of 0.013μg L^-1and 0.022μg L^-1for MC-RR and MC-LR,respectively,under the optimum conditions.This method has great application potential in water quality monitoring by using CDs-FITC-SiO₂@MIP as a promising candidate for monitoring MCs in complex systems.2 Investigation on determination of microcystin-LR in water by magnetic microsphere competitive immunoassayIn this work,a method for precise detection of MC-LR in water by competitive immunity is proposed based on Fe₃O₄@SiO₂-NH₂nanocomposite material,which is modified with microcystin-LR antibody on its surface.The magnetic immune composite was prepared（Fe₃O₄@SiO₂-NH₂-Ab）,MC-LR coupled glucose oxidase（GOx）complex was synthesized（GOx@MC-LR）.Through MC-LR and GOx@MC-LR to Fe₃O₄@SiO₂-NH₂-Ab competitive combination,in the presence of horseradish peroxidase（HRP）,the hydrogen peroxide produced by glucose catalyzed by MC-LR coupled with GOx complex in the supernatant catalyzes ADHP to produce strong red fluorescence,thus realizing the quantitative detection of MC-LR.Under the optimum conditions,the fluorescence intensity increases within the dynamic working range of 0.1～250μg L^-1with the increase of MC-LR concentration,and the detection limit is 0.011μg L^-1.The established immunoassay has good reproducibility and accuracy.This method has broad application prospects in the specific detection of MC-LR.