Studies On Electrochemical Immunosensor For Detection Of Tumor Markers Based On Functionalized Graphene Composites

Cancer has become a chronic disease,most of which can be prevented and cured.If cancer can be prevented and screened,it can be found and treated early,thus reducing cancer mortality.Tumor markers are biological molecules that exist in blood,body fluids or tissues.They are markers of normal or abnormal processes,conditions or diseases.Tumor markers are objective reflections and evaluations of normal biological processes,pathogenic processes or pharmacological reactions to therapeutic interventions.The content of tumor marker in vivo can be used for the risk assessment,screening,differential diagnosis,prognosis judgement,treatment response prediction and disease progression monitoring of the cancer.Therefore,rapid and sensitive quantitative detection of tumor markers is of great significance for the treatment of cancer and the reduction of mortality.The electrochemical immunosensor has attracted wide attention because of its simple operation,high sensitivity,rapid detection and low cost.In this paper,based on the technology of signal amplification of nanomaterials,four new electrochemical immunosensors are constructed for the detection of tumor markers by using functionalized graphene to amplify the electrochemical signals by increasing the amount of antibodies loaded on the sensing interface.The concrete works carried out are as follows:1.A label-free electrochemical immunosensor based on N-doped graphene-gold nano-chitosan?N-GS-Au NPs-Chit?composite was constructed for the detection of alpha-fetoprotein?AFP?.The preparation method of composite material is simple and the thickness of composite film is controllable.N-GS not only improved the conductivity of the composites,but also provided a large number of active sites for the load of Au NPs and increased the load of antibodies,thus realizing the amplification of electrochemical signals.Under the optimum conditions,by using hexacyanoferrate as an electrochemical probe,the immunosensor has a detection limit as low as 1.6 pg mL^-1 and a linear analytical range that extends from 5 pg mL^-1to 50 ng mL^-1.It possesssed good selectivity,reproducibility and stability,and can be successfully used for the detection of AFP in serum samples.2.A novel three-dimensional?3D?structural nano-PEDOT-graphene aerogels?nano-PEDOT-GAs?composite was designed via the in-situ polymerization of nano-PEDOT on porous 3D GAs.Featuring the excellent biocompatibility,high specific surface area and good conductivity of Au NPs/nano-PEDOT-GAs,a highly sensitive label-free immunosensor was developed using Au NPs/nano-PEDOT-GAs as signal amplification platform for detecting prostate specific antigen?PSA?.Under the optimal conditions,the fabricated immunosensor presented a good linear in the analytical range of 0.0001-50 ng mL^-1 with a low detection limit of 0.03 pg mL^-1?S/N=3?,high selectivity against other serum interfering substance and good stability and reproducibility,which provides a promising platform for the clinical immunoassay of PSA.3.A three-dimensional porous network graphene aerogels?GAs?with large specific area and excellent conductivity was loaded with the?-cyclodextrin polymer?P?-CD?to serve as a support for immobilization of antibodies.A highly sensitive immunosensor for the cancer marker carbohydrate antigen 15-3?CA15-3?was designed based on the use of P?-CD/GAs.The large specific area of GAs warrants high loading with antibodies,and their excellent electrical conductivity warrants strong electrical signals.Based on the synergistic effect of GAs and P?-CD,an immunoassay was designed that is making use of hexacyanoferrate as an electrochemical probe and having a pleasantly low working potential of 0.2 V?vs.SCE?.Response is linear in the 0.1 mU mL^-1 to 100 U mL^-1 activity range,and the lower detection limit is 0.03 mU mL^-1?at S/N=3?.The immunoassay is stable,selective and reproducible.It was applied to the analysis of spiked samples,and results were satisfactory4.A label-free immunosensor based on Au nanoparticles?Au NPs?/MoS₂-graphene aerogels?GAs?nanocomposite for the detection of prostate specific antigen?PSA?.In the sensing platform,MoS₂ was used as the support to control the tight restacking of graphene sheets?GS?during the hydrothermal reduction process and enlarge the specific area of GAs.The obtained MoS₂-GAs nanocomposite with porous network structure as the carrier provided large specific area for Au NPs,which further improved the load of antibody.Thus,the proposed immunosensor presented wide linear range from 0.01 pg mL^-1 to 50 ng mL^-1 with a low detection limit of 0.003 pg mL^-1.In addition,the immunosensor also performed with acceptable stability,good reproducibility and selectivity.Moreover,the good recoveries were obtained when the immunosensor was applied to analyze PSA in human serum,which will provide a promising application for early diagnosis of PSA.