Study On The Sensitive And Specific Biosensors For The Rapid And On-site Detection Of Copper And Uranyl Ion In The Aqueous Environment

Excessive intake of copper is connected to a variety of biological toxicity,and the uranium not only has radioactive toxicity but also has chemical genotoxicity,which is similar to that of heavy metal.The copper and uranium will harm human health via drinking water and biological chain.On-site and rapid detection of them is one of the most effective methods to prevent their damage.Therefore,the development of the rapid and on-site methods for detecting copper and uranium is of great significance.The main aim of this study is to develop the sensitive and specific methods for detecting trace Cu2+ and UO22+,in hope of providing a reliable and simple method for on-site detection of Cu2+ and UO22+ in aqueous environment.The main content including:(1),Designed and synthetized a novel phosphatidylserine-functionalized Fe3O4@SiO2NPs(nanoparticles)and enzyme-encapsulated liposome for the visual detection of Cu2+ by employing phosphatidylserine for Cu2+ recognition and enzymatic catalysis/oxidation of 3,3’,5,5’-tetramethylbenzidine sulfate(TMB)as signal generator.The phosphatidylserine(1,2-doleoyl-sn-glycero-3-phospho-L-serine,DOPS)was covalently assembled on the Fe3O4@SiO2NPs surface to obtain DOPS-functionalized Fe3O4@SiO2NPs,and was used to encapsulate horseradish peroxidase(HRP)to form HRP-encapsulated DOPS liposome.It was demonstrated that DOPS-functionalized Fe3O4@SiO2NPs can specifically bind HRP-encapsulated DOPS liposome in the presence of Cu2+ at basic pH.The HRP-encapsulated DOPS liposome bound on the DOPS-functionalized Fe3O4@SiO2NPs was then separated from solution with a magnet.Upon the addition of TMB-H2O2 solution,the HRP-encapsulated DOPS liposome bound on the DOPS-functionalized Fe3O4@SiO2NPs was broken to release HRP,and the released HRP catalyzes the H2O2-mediated oxidation of TMB,which gives rise to a change from colourless to blue in solution colour and a new absorption peak at 652 nm.This provided a sensing platform for the sensitive,specific and field-portable colorimetric detection of Cu2+.By using the sensing platform,a selective and sensitive visual sensor for the detection of Cu2+ was developed.The proposed method has outstanding advantages including adequate sensitivity,shorter analysis time,relatively low cost,operation at room temperature and stronger resistibility to the matrix.It can be used to detect as little as 0.1-0.5 μM of Cu2+ in river water using naked-eye observation and 0.05μM of Cu2+ in river water using UV-visible spectrophotometry when 2 mL of the water sample was used for detection,within 15 min and with a recovery of 95-101%and a RSD<5%(n=5).The above features make our sensor a promising approach for the rapid and on-site detection of trace free copper ions in aqueous environments by only naked-eye observation.(2),A new "turn-on" fluorescence biosensor for the rapid detection of UO22+was developed based on UO22+-specific DNAzyme and DNA-stabilized silver nano-cluster(AgNCs).We designed the DNA sequence and synthesized the nucleic-acid-stabilized AgNCs,which has emission wavelength of 616 nm.We demonstrated that the nucleic-acid-stabilized AgNCs can be firmly adsorbed on the surface of graphene oxide(GO),and resulting in fluorescence quenching.Upon addition of UO22+,UO22+ can specifically cleave DNAzyme to release a single-strand DNA,which was design to part complement with the template DNA of AgNCs.The released single-strand DNA can hybridize with template DNA of AgNCs,and thus release the DNA-stabilized AgNCs from GO since GO has a weak adsorption to duplex DNAs,which leads to the recovery of fluorescence.This provided a sensing platform for the rapid,simple and sensitive fluorescent detection of UO22+.By using the sensing platform,a sensitive and selective "turn-on" fluorescent method for the rapid detection of UO22+ has been developed.The proposed method has obvious analytical advantage such as relatively high sensitivity and good stability,short analytical time and low cost.It can be used to detect as low as 0.42 μg/L(1.58 nM)of UO22+ in aqueous environment within 30 min with a recovery of 96%-104%and a RSD<5%(n = 5).The success of this study provides a promising alternative for the rapid and on-site detection of UO22+ in environmental monitoring.