Preparation Of Carbon-based Nanocomposites And Their Applications In Electrochemical Biosensing

Electrochemical biosensor is an analytical method developed by combining electrochemical technology with biosensors,which not only has the characteristics of electrochemistry,but also has the functions of biosensor.On the basis of high sensitivity,high selectivity and low cost,electrochemical biosensor also has the advantages of fast analysis and simple operation,and it is widely used in the determination of chemical and biochemical analytes in many fields including clinical analysis and diagnosis,food testing,environmental monitoring,biological drugs,and so on.Carbon-based materials such as graphene and covalent organic frameworks(COFs)are commonly used as carrier materials for the preparation of nanocomposites.Graphene has the characteristics of large specific surface area and excellent electrical conductivity.COFs have the advantages of good thermal/chemical stability,ultra-high specific surface area and unique homogeneous pore structure.Both of these carbon-based nanomaterials have great potential applications in the field of biosensing.In this thesis,novel carbon-based nanocomposites were prepared by chemical doping,in situ growth or compounding methods using carbon-based nanomaterials as substrates,which were used for the construction of electrochemical biosensors to achieve efficient detection of disease-related biomarkers.The main research contents and innovation points are as follows:1.An electrochemical sensor based on nitrogen-doped three-dimensional porous graphene aerogel(HNGA)was prepared for the detection of small biological molecules.Three-dimensional porous graphene hydrogel was synthesized by one-step hydrothermal method,then it was freeze-dried and modified by high-temperature annealing to obtain HNGA.It had the unique porous structure and excellent electrocatalytic activity.The HNGA modified glassy carbon electrode(HNGA/GCE)could be used for the individual and simultaneous detection of ascorbic acid(AA),dopamine(DA)and uric acid(UA).The detection limits of the sensor were 16.7 μM,0.22 μM and 0.12 μM for AA,DA and UA,respectively(S/N=3).In addition,HNGA/GCE could be successfully applied to the analytical detection of real samples.2.An electrochemical biosensor based on carbon nanotubes and platinum nanoparticles functionalized COF(COF/Pt/MWCNT-COOH)was prepared for the detection of DA.TAPB-DVA-COF was synthesized by the atmospheric pressure solution method,followed by the modification of Pt nanoparticles into COF nanoparticles using the in-situ growth method.After that,a novel COF-based nanocomposite(COF/Pt/MWCNT-COOH)was obtained by adding a conductive agent carboxyl-functionalized multi-walled carbon nanotubes(MWCNT-COOH)during the synthesis process.It exhibited a large specific surface area,good electrical conductivity and electrocatalytic activity.The COF/Pt/MWCNT-COOH modified glassy carbon electrode(COF/Pt/MWCNT-COOH/GCE)showed excellent analytical performance for DA in the concentration range of 2 μM～500 μM,with a detection of 0.67 μM(S/N=3).In addition,COF/Pt/MWCNT-COOH/GCE was also used successfully for the detection of DA in real human serum samples.3.An electrochemical immunosensor based on COF nanocomposite and enzyme catalytic signal amplification was prepared for the detection of cardiac troponin I(cTnI).TAPB-DMTP-COF was synthesized in acetonitrile solution using 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-dimethoxy-p-phenylene terephthalaldehyde(DMTP)as precursors.After that,gold nanoparticles,detection antibody Ab2 and horseradish peroxidase(HRP)were modified progressively to COF nanoparticles to obtain nanocomosites(HRP-Ab2-Au-HRP).The high porosity and good biocompatibility of COF made it an excellent carrier for loading biological enzymes.Gold nanoparticles on the surface of COF not only provide a platform for Ab2 loading,but also improve the electrical conductivity of the nanocomposite.Under the synergistic effect of hydrogen peroxide and HRP,hydroquinone in the electrolyte was catalytically oxidized to benzoquinone(BQ),and then BQ was reduced on the electrode surface to generate electrochemical signals.The constructed electrochemical immunosensor showed an ideal linear response to cTnI in the concentration range of 5 pg/mL to 10 ng/mL,with a detection limit of 1.7 pg/mL.In addition,the electrochemical immunosensor demonstrated good recovery and reproducibility in the detection of real samples.4.An electrochemical biosensor based on ferrocene functionalized COF and target catalytic hairpin self-assembly(CHA)strategy was prepared for the detection of microRNA-21(miR-21).The COF nanoparticles were prepared by an atmospheric pressure solution method at room temperature.Then the COF was progressively modified with gold nanoparticles,the electroactive material ferrocene(Fc)and complementary DNA probe L1 to obtain the electroactive nanocomposite COF/Au/Fc/L1,which had large specific surface area,outstanding catalytic activity and favourable biocompatibility.It was combined with a DNA tetrahedral nanostructure biosensing interface and CHA strategy to construct an electrochemical biosensor for the accurate and sensitive detection of miR-21.The electrochemical biosensor had a good linear response to the target miR-21 in the concentration range of 1 fM to 10 nM,with a detection limit as low as 0.33 fM(S/N=3).Meanwhile,the method was used for the detection of miR-21 in clinical samples with good accuracy and precision.