Novel Optically Modified Carbon Nitride And Its Application In Electrochemical Aptasensor Of B-amyloid Oligomers

Objective The current researches based on AβOs electrochemical aptasensor have the following shortcomings,including complex and time-consuming process of synthesizing nanomaterials,single types of electrochemiluminescence(ECL)active substances and limited efficiency,outdated sensing strategies and limited sensitivity.In this thesis,we focuse on simplifying the process of nanomaterial preparation and sensor construction,enriching the types of ECL active substances as well as improving their luminous efficiency and optimizing the sensing strategy to establish two novel AβOs electrochemical aptasensors with high sensitivity,selectivity and stability.These could provide charming ideas for the subsequent identification and quantitative detection of trace biomarkers.Methods In the thesis,two novel optically modified carbon nitride were synthesized by a new co-precipitation method and a fast one-pot method,respectively,including magnetic optically modified carbon nitride(MCNS)and optical silver-based modified gel(Ag CNS).Field emission scanning electron microscopy(FESEM),Fourier transform infrared spectroscopy(FTIR)and inverted fluorescence microscopy(IFM)for morphological characterization and composition characteristics research.Electrochemical impedance spectroscopy(EIS),cyclic voltammetry(CV),differential pulse voltammetry(DPV)and ECL technology for photoelectric performance research.The optimization and stability study of main experimental parameters and detection conditions were carried out by ECL.Two switchable AβOs electrochemical aptasensors(THS-EA)based on triple helix switches were constructed,by using unlabeled Apt as the identification element with ferrocene and Ag CNS-labeled complementary probes(Fc-CP,Ag CNS@CP)as signal probes,respectively.The formation and unwinding of THS was controlled by the signal modes to obtain AβOs concentration-dependent signal intensity changes.The construction process of these aptasensors were monitored by EIS and CV,and the sensitive analysis and specific detection of different concentrations of AβOs were achieved through DPV and ECL.The analytical performances of the two aptasensors are systematically studied through methodological research and feasibility validation.Results The results of a series of studies show that both MCNS and Ag CNS show irregular nano-aggregate structures that are different from ultra-thin CNS.In addition,both MCNS and Ag CNS emit bright blue light and exhibit superior photoelectric performance and good stability.The linear ranges of the two AβOs electrochemical aptasensors are 1 f M ～10 p M and 0.5 f M ～ 5 p M,respectively.The limits(LOD)were0.47 f M and 0.21 f M,respectively.They were applied to artificial cerebrospinal fluid(A-CSF)samples,the recoveries ranged from 94.0% to 110.0% with RSD less than3.75%.Conclusions The prepared MCNS and Ag CNS have excellent luminous efficiency,superior photoelectric performance and good stability,which can be used as biomolecular tags or electrode modification materials in constructing a series of electrochemical biosensors.The electrochemically active signal probes Fc-CP and Ag CNS@CP are combined with unlabeled Apt to successfully construct a series of THS-EAs,which are flexible in configuration,easy to control,and have good stability,sensitivity and reproducibility.It is convenient to realize the sensitive analysis and specific detection of different concentrations of AβOs,and provides new ideas for the subsequent research of AD biomarkers and detection of other biomolecules.