Studies On Electrochemical Immunosensors For Human Chorionic Gonadotrophin And Carbohydrate Antigen 19-9

Electrochemical immunosensor,with the advantages of rapid,high sensitivity,nice selectivity and easy automation,is a kind of the biosensors that linking electrochemical method and immunological techniques.In the design and fabrication of immunosensors, the method and material used to immobilize biomolecules is one of a most important factors for the performance of immunosensor,such as sensitivity,response time, selectivity and lifetime.Nanoparticles exhibiting a large specific surface area and strong adsorption,can increase the adsorption amount of antibody and antigen.At the same time,nanoparticles can provide good biocompatibility with the environment to retain the biomolecules biological activities,in order to improve the sensitivity and lifetime of the immunosensor.In this paper,based on electropolymerization and electrostatic interaction we combined the advantgaes of specific electrochemical properties of carbon nanotubes,specific surface area and good biocompatibility of gold nanoparticles to construct three different amperometric immunosensors.The main works and conclusions are included as follows:1.Based on nano-Au/Co(bpy)₃³⁺ /DNA/ZrO₂ modified gold electrode for detection of human chorionic gonadotrophinA new ampermetric immunosensor for human chorionic gonadotrophin(HCG) has been fabricated through tris(2,2'-bipyridyl) cobalt(â…¢)(Co(bpy)₃³⁺) and gold nanoparticles on the zirconia(ZrO₂) and DNA modified gold electrode.The ZrO₂-DNA complex membrane not only enhances the electrode surface area to adsorb more antibodies,but also can act as a charge carrier to improve the electron transfer.Gold nanoparticles with larger specific surface area and desirable biocompatibility can also adsorb more antibodies without loss of their biological activities.The fabrication process of the immunosensor was characterized by scanning electron microscopy (SEM),electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV). Under the optimized condition,the proposed immunosensor exhibited a good electrochemical behaviour to HCG in the range of 1.0 to 50.0 mIU/mL and 50.0 to 150.0 mIU/mL with the detection limit of 0.4 mIU/mL.The immunosensor showed high sensitivity, selectivity and stability.2.Based on nano-Au/MB/DNA-MWNTs modified glassy carbon electrode for detection of human chorionic gonadotrophinA novel ampermetric immunosensor for human chorionic gonadotrophin(HCG) based on good biocompatibility of DNA and multi-walled carbon nanotubes(MWNTs) and strong adsorption possibility of gold nanoparticles has been developed.The fabrication steps of the immunosensor as follow:firstly,DNA-MWNTs was immobilized onto the surface of glassy carbon electrode;secondly,methylene blue(MB) was adsorbed onto modified electrode surface with the electrostatic interaction and chemisorbed;thirdly,gold nanoparticles were again adsorbed onto the electrode surface, which can offer a favorable microenvironment and biocompatibility to immobilize anti-HCG;finally,horseradish peroxidase(HRP) instead of bovine serum albumin was employed to block sites against non-specific binding and amplified the current signal of the antigen-antibody reaction.The characteristics of the resulting immunosensor at different stages of modification was studied by using scanning electron microscopy (SEM) and cyclic voltammetry(CV).The performances of the modified electrode were studied in detail.The cathodic peak current response of CVs were proportional to the concentration of HCG in the range of 0.1 to 10 mIU/mL and 10 to 300 mIU/mL with the dertection of 0.04 mIU/mL.The resulting immunosensor exhibited a simple pretreatment procedure,high sensitivity,broader measuring range,and low detection limit.3.Based on multi-walled carbon nanotubes and cobalt hexaeyanoferrate nanopartieles(CoHCF) modified glassy carbon electrode for carbohydrate antigen 19-9A convenient and effective strategy based on the unique characteristics of chitosan (CS)-multiwalled carbon nanotubes(MWNTs) composite membrane,favorable electroactive substance cobalt hexacyanoferrate nanoparticles(CoHCF) and gold nanoparticles with the advantage of good biocompatibility and strong adsorption possibility is used to develop a highly sensitive amperrnetric immunosensor for carbohydrate antigen 19-9(CA19-9).The fabrication steps of the immunosensor as follow:firstly,CS-MWNTs was immobilized onto the surface of glassy carbon electrode;secondly,CoHCF as an electroactive substance,were immobilized on the layer of CS-MWNTs membrane with the electrostatic interaction;at last,gold nanoparticles was assembled on the surface of CoHCF for the immobilization of anti-CA199.Scanning electron microscopy(SEM) and cyclic voltammetry(CV) were applied to characterize the electrochemical properties of modified process.Effect of the pH of working buffer,incubation temperature and time were studied in detail for optimization of analytical performance.Under optimal condition,the peak current of CV of the immobilized anti-CA199 decreased linearly with increasing CA19-9 concentration in the range of 1.0～90.0 U/mL,with the detection limit of 0.4 U/mL at three times background noise.The immunosensor showed a lower detection limit,high sensitivity,good repeatability and stability.