Preparation And Application Of Carbon Nanomaterials Electrochemical Immunosensors For Tumor Markers Detection

Malignant tumors is a one of serious threat to human health and life. The incidence of malignant tumors are connected with the percent of specific biological markers in the body. Therefore, trace amounts of the tumor markers detection play an important role in clinical diagnose. Compared with other immunoassays, electrochemical immunosensors are of great interest because of excellent properties. An important issue of the electrochemical immunosensors is focuses on the sensitivity enhancement. We made use of nanomaterial and nanomaterial nanocomposites with a series of excellent properties to construced the sensitive electrode interface and electroactive nanoprobe for signal amplification. Thus, in this paper the work focus on two aspects to enhance the sensitivity of the immunosensors in the following five areas:1. A electrochemical immunosensor was fabricated based on gold nanoparticles(Au NPs) dotted carbon nanotube as the sensor platform.In this work, Au NPs was electrodeposied on multi-walled carbon nanotubes(MWCNTs) modified glassy carbon electrode(GCE) by potentiostatic electrodeposition and further used for fixing antibody. Fe(CN)63-/4- acted as signal molecule, we successfully described a simple electrochemical immunosensor. SEM showed that Au NPs were uniformly distributed on the surface of MWCNTs. Cyclic voltammograms(CV) proved MWCNTs and Au NPs can also accelerate the electron transfer on the electrode surface to amplify the electrochemical signal due to the outstanding electric conductivity. Experimental results revealed that the proposed immunosensor enabled the determination of carcinoembryonic antigen(CEA) and exhibited aceeptable stability and reproducibility.2. Electrochemical immunosensor for the determination of CEA using Au NPs-(prussian blue(PB)-a graphene and carbon nanotubes)n muti-layer films as the sensor platform.In this work, it was based on the use of a glassy carbon electrode(GCE) modified with a ordered multi-layer films made from PB, graphene and carbon nanotubes via alternate electrodeposition and self-assembly. We describe a sensitive, label-free electrochemical immunosensor for the detection of carcinoembryonic antigen. Au NPs were electrostatically absorbed on the surface of the film and used for the immobilization of antibody. The possibility of leakage of PB from the electrode surface was decreased and the stability of the biosensor was improved obviously using multi-layer films. PB acted as signal molecule, which avoided the trouble of adding a mediator to the sample solution. The fabrication process of immunosensor was characterized by scanning electron microscopy(SEM) and electrochemical measurements, respectively. Under the optimal conditions, the decrease of intensity of the peak current of PB is linearly related to the concentration of CEA in two ranges(0.2-1.0, and 1.0-40.0 ng m L-1), with a detection limit of 60 pg m L-1(S/N=3).3. Dual signal amplification of horseradish peroxidase functionalized nanocomposites as trace label for the electrochemical detection of CEA.In this work, we prepared horseradish peroxidase(HRP) functionalized nanocomposites as a novel trace label, Au NPs-thionine functionalized carbon nanotubes(Thi-CNTs) as the sensor platform, we designed a highly sensitive electrochemical immunosensor. CNTs as templates, we synthesized CNTs-polyaniline(PAN) nanocomposites with uniform core-shell structures by the oxidant(NH4)2S2O8, due to electrostatic interaction, the Au NPs were assembled on the surface of PAN@CNTs nanocomposites. The preparation of the labels were performed by one pot assembly of HRP and signal antibody on Au NPs-PAN@CNTs. Both high-content HRP and the Au NPs-PAN@CNTs amplified the detectable signal. The immunosensor displayed an excellent linear response for the detection of CEA ranging from 0.02 to 80.0 ng m L-1 with a detection limit of 0.008 ng m L-1.4. Simultaneous electrochemical detection of CEA and AFP using functionalized graphene nanocomposites as non-enzymatic labels.In this work, due to non-enzymatic multiple-label method, we developed a novel electrochemical immunosensor for simultaneous detection of CEA and AFP. Gold microstructures with large effective area were used to immobilize the capture antibodies and provide a biocompatible microenvironment for the immobilization of antibody. We synthesized PB@reduced graphene oxide(r GO) and Thi@r GO two nanocomposites through the π-π stacking and PDDA as linkage reagents, Au NPs-PB@r GO and Au NPs-Thi@r GO employed as distinguishable signal tags. Experimental results revealed that this sandwich-type immunoassay displayed an excellent linear response with linear range 0.6-80.0 ng m L-1 for both analytes, with the detection limit was 0.12 ng m L-1 for CEA and 0.08 ng m L-1 for AFP, respectively.5. Simultaneous electrochemical detection of CEA and AFP using gold nanoparticles decorated MWCNTs as signal enhancers.In this work, Au NPs@MWCNTs nanocomposites was fabricated via a simple sonication-induced assembly. A novel sandwich-type electrochemical immunosensor based on the signal amplification strategy of the Au NPs@MWCNTs nanocomposites has been developed for simultaneous detection of CEA and AFP. Due to the nanocomposites with excellent properties such as large effective area and good electrochemical conductivity, the Au NPs@MWCNTs could load numerous secondary antibody and trace lables. Experimental results revealed that the metal ions functionalized nanocomposites as trace labels could amplified the detection signal, this immunosensor displayed an excellent linear response with linear range 0.01-60.0 ng m L-1 for both analytes, with the detection limit of 3.0 pg m L-1 for CEA and 4.5 pg m L-1 for AFP. In addition, the multiplexed immunoassay exhibited good sensitivity and selectivity.