The Fabrication And Application Of Electrochemical Immunosensor Based On Polypyrrole Composite Nanomaterials

The liver plays a role in glycogen conversion and detoxification in the human body.It also is an important metabolic organ of the human body.However,hepatitis B and liver cancer are harmful to the liver and seriously threaten people’s lives.Most liver cancers are diagnosed at a later stage,which is an important reason for the high mortality rate of liver cancer.In clinical practice,detecting the level of tumor markers in serum is good for guiding significance for tumor screening,judging development degree,and observation of therapeutic effects.Therefore,the development of rapid,efficient and sensitive methods for detecting tumor markers is conducive to the screening and diagnosis of cancer.Electrochemical immunosensor is a kind of detection method,which combines immunoassay and electrochemical analysis.It has the advantages of high sensitivity,strong specificity and simple operation,which is favored by analysts.The synthesis method of polypyrrole is environmentally friendly,simple,and it also has the advantages of good electrical conductivity,biocompatibility,and easy functionalization,and has a good application prospect.The main task of this study is to prepare polypyrrole nanocomposites with high conductivity and high catalytic activity,and apply them to amperometric immunosensors.The immunosensors are used to detect hepatitis B surface antigen（HBs Ag）and alpha-fetoprotein（AFP）and carcinoembryonic antigen（CEA）,respectively.1.An amperometric immunosensor was developed for quantitative detection of HBs Ag.In the immunosensor,gold nanoparticles loaded on polypyrrole nanosheets（Au NPs/PPy NS）were used as the platform,and ruthenium platinum core-shell nanodendrites loaded on amino functionalized graphene（Rh@Pt NDs/NH₂-GS）were used as the label of secondary antibodies.Rh@Pt NDs/NH₂-GS has high catalytic activity for hydrogen peroxide,which can convert the signal of antigen concentration into electrical signal and realize the amplification of signal;Au NPs/PPy NS with high conductivity can accelerate the electron transfer on the surface of electrode,thus increasing the sensitivity of immunosensor.The time-current curve method was used under the optimal experimental conditions to test the quantitative detection of HBs Ag.2.A label-free amperometric immunosensor was fabricated to detect AFP quantificationallybased on platinum nanodendrites loaded on poly（diallyldimethylammonium chloride）functionalized molybdenum disulfide nanosheet hybrid polypyrrole nanotubes（Pt NDs/PDDA/Mo S₂@PPy NTs）.Pt NDs and Mo S₂nanosheets had excellent catalytic activity to hydrogen peroxide.Pt NDs and PPy NTs with good conductivity can accelerate electron transfer.PDDA can provide loading sites to Pt NDs,which enhanced the stability of materials.It has been proved by electrochemical and photochemical methods that Pt NDs/PDDA/Mo S₂@PPy NTs have good electrical conductivity,stability and high catalytic activity for hydrogen peroxide.Under the optimal experimental conditions,the immunosensor can detection AFP quantificationally.3.Gold-palladium core-shell nanodendrites loaded on ferrous-chitosan functionalized polypyrrole nanotubes(Au@Pd NDs/Fe²⁺-CS/PPy NTs)and gold nanoparticles loaded on amino functionalized grapheme（Au NPs/NH₂-GS）were prepared.An amperometric immunosensor were fabricated by Au@Pd NDs/Fe²⁺-CS/PPy NTs and Au NPs/NH₂-GS as label of secondary antibodies and platform,respectively,for quantitative detecting CEA by time-current curve method and square wave pulse voltammetry.Due to good electron conduction and immobilization ability,Au NPs/NH₂-GS can accelerate electron transfer on the surface of the electrode,and immobilize a sufficient amount of primary antibodies,which was a good foundation for sensitive detection of immunosensors.In the composite,Fe²⁺and Au@Pd NDs were used as catalysts to catalyze the reduction of hydrogen peroxide for achieving signal amplification,when hydrogen peroxide acted as the electroactive substance via the time-current curve method;Fe²⁺and PPy NTs as electroactive substances were reduced to achieve signal amplification,when measured by square wave pulse voltammetry.The immunosensor exhibited large linear range for CEA via both time-current curve method and square wave pulse voltammetry.In the overlapping portions of the linear range,the detection result can be mutually verified by two detection methods,which improved the reliability of the sensor detection.