Studies On Novel Electrochemical Aptasensor And Amperometric Immunosensor Based On Nano-materials

Electrochemical immunosensors,which combine the technology of electrochemical analysis and immunology,have been applied to a wide range of analytical areas,including bioassay,clinical diagnosis and environmental monitoring,due to their advantages high sensitivity,good selectivity, miniaturization,easy automation and potential ability for real-time analysis.The method and material used to immobilize biomolecules is one of the crucial factors in the design and fabrication of immunosensor.Nano-materials,exhibiting large specific surface area,good biocompatibility and strong adsorption capacity,are favourable for constructing biosensors,which not only retain the biological activities of biomolecules,but also enhance the sensitivity and service life of the sensors.Aptamers are oligonucleotides selected from random sequence nucleic acid libraries using SELEX(systemic evolution of ligands by exponential enrichment).Due to their high affinities and specificities in binding to proteins,amino acids,medicine,inorganic ions sand other macromolecules,aptamers have been applied to a wide range of analytical areas,such as biosensing,drug testing,and medical diagnosis.Electrochemical aptasensors,which are based on the specificity of aptamer-target recognition with electrochemical transduction for analytical purposes,have received particular attention in recent years.The main works of the research paper are included as follows:Part 1 Highly sensitive,reagentless amperometric immunosensor based on a novel redox-active organic-inorganic composite filmA new highly sensitive amperometric immunosensor for the determination of carcinoembryonic antigen(CEA) had been constructed by employing a novel organic-inorganic composite film coupled with gold nanoparticles.A new porous organic material synthesized with 3,4,9,10-Perylenetetracarboxylicdianhydride(PTCDA) and ethanediamine was coated on the surface of PB film to obtain a stable organic-inorganic composite film.This porous organic material (PTC-NH₂) provided abundant amino-groups to assemble gold nanoparticles(nano-Au) for immobilization of carcinoembryonic antibody(anti-CEA).Under optimal conditions,the resulting immunosensor displayed a high sensitivity for the detection of CEA,and exhibited high selectivity, long-term stability and good reproducibility.Part 2 Highly sensitive reagentless amperometric immunosensor based on layer-by-layer assembly of redox-active organic-inorganic composite film for determining prostate specific antigenA new highly sensitive amperometric immunosensor for the detection of prostate specific antigen (PSA) has been constructed by means of covalent bonding to immobilize prostate specific antibody (anti-PSA) on multilayer organic-inorganic redox-active composite film/gold nanoparticle(nano-Au) modified glassy carbon electrode surface.A new porous organic material synthesized with 3,4,9,10-Perylenetetracarboxylicdianhydride(PTCDA) and ethanediamine was coated on the surface of PB film to obtain a stable multilayer organic-inorganic composite films.The composite film provided abundant amino-groups to assemble gold nanoparticles(nano-Au) for immobilization of anti-PSA.The preparation procedure of the immunosensor was further investigated by cyclic voltammetry(CV).In addition,the performance and influencing factors of the resulting immunosensor were studied in detail.Under optimal conditions,the resulting immunosensor displayed a high sensitivity for the detection of PSA,and responsed to the PSA concentration in the range from 0.5 to 16 ng/mL(r=0.985) with a detection limit of 0.02 ng/mL.Part 3 Highly sensitive,reusable electrochemical aptasensor for adenosineA reusable electrochemical aptasensor for highly sensitive detection of small molecules had been developed using adenosine as a model molecule.The sensing interface was fabricated by self-assembling the part DNA duplex hybridized by 5'-thiolated part complementary strand(TPCS) and 3'-ferrocene(Fc)-labeled adenosine-binding aptamer strand(FABA) through S-Au bonding on a gold electrode surface.The aptasensor was characterized electrochemically by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).The CV of the resulting aptasensor showed a linear response of the change of Fc reduction signal to the increase of the adenosine concentration in the range of 5.0×10^-8～1.5×10^-5 mol/L with a linear correlation of r= 0.9898 and a detection limit of 1.65 x 10^-8 mol/L.