New Biosensing Method Based On DNA Walker And Graphite Phase Carbon Nitride Nanosheet

Due to the advantages of convenient synthesis,simple operation,fast response,high sensitivity,and good specificity,fluorescent biosensor s have been widely used in biosensing,chemical analysis,medicine and health,environmental detection and other fields.With the rapid development of society,while the level of human science and technology has improved,more and more new analytical topic s have emerged in the fields of biology,chemistry,medicine,and environment.Therefore,it is necessary to develop fluorescent biosensors with good stability,high sensitivity,good specificity and comprehensive functionality.In this paper,two new fluo rescent biosensors were constructed based on DNA walker and graphite phase carbon nitride nanosheet for the specific detection of ribonuclease H(RNase H)and ascorbic acid(AA),respectively.The details are as follows:In the second chapter,ribonuclease H(RNase H),an intracellular endoribonuclease,participates in multiple cellular processes within the cell,especially plays a key role in the retroviral recombination process and is related to the formation of various diseases.We report a novel fluores cence sensing strategy based on an RNase H-powered DNA walking machine.The DNA walking machine is composed of a small quantity DNA walker strands and abundant FAM-labeled DNA-RNA chimeric strands on a single gold nanoparticle(Au NP).In the presence of the RNase H,the RNase H can specifically degrade the RNA fragment in DNA-RNA chimeric hybrid duplex and trigger the autonomous movement of DNA walker strand on the Au NP surface.During this process,each step of the walking can release the FAM-labeled RNA from the surface of Au NP,realizing the signal amplification for RNase H sensing.In addition,this method has been successfully utilized for the RNase H activity detection in the complex system and applied for the screening of related inhibitors.The sensor has the characteristics of simple structure,fast response to the target,good selectivity and high sensitivity,which provides a novel fluorescent sensing platform for the detection of RNase H activity.In the third chapter,ascorbic acid(AA)is an imp ortant biomolecule that participates in many biochemical processes and plays an important role in maintaining normal metabolism and organ function.Based on the fluorescence quenching effect of MnO₂ nanosheets on the graphite carbon nitride(g-C₃N₄)nanosheets,a novel and label-free fluorescent biosensor was constructed for the detection of AA.The sensor is constructed by in-situ synthesis of MnO₂ nanosheets on g-C₃N₄ nanosheets to form the g-C₃N₄-MnO₂ nanocomposites.In this sensor,the MnO₂nanosheets as a fluorescence quencher can quench the fluorescence of the g-C₃N₄ nanosheets,and the fluorescence signal of the system is very weak.When AA is present in the system,it can reduce the MnO₂ nanosheets in the nanocomposites to produce Mn²⁺,thereby restoring the fluorescence of the g-C₃N₄ nanosheets.By detecting the intensity of the fluorescent signal in the system,the sensor can achieve the rapid and accurate detection of AA.The method requires lower raw material cost,simpler synthesis method,no fluorescent label,and has short reaction time,high sensitivity,and good application potential.