Construction Of Sensitive Interfaces Based On Amino-functionalized Carbon Nanotubes And Electrochemical Application On Biological Molecules

Objective:To investigate effects of sensitive interfaces based on amino-functionalized carbon nanotubes to three kinds of substances including carcinoembryonic antigen, quercetin and kaempferol, carbendazim.Methods:1. Carcinoembryonic antigen(CEA) is one of the important tumor markers that can be used in the differential diagnosis, disease monitoring and treatment evaluation of colorectal, breast and lung cancer and other malignancies. In this study, amino-functionalized carbon nanotubes(NH2- MWCNT), thionine(THi) and gold nanoparticles(Au NPs) were mixed together, NH2- MWCNT and THi chemically bonded with Au NPs by the end of-NH2. Next, the mixture was dropped onto surface of glassy carbon electrode(GCE), further fixed with carcinoembryonic antigen antibody(anti-CEA) by Au-N bonding and finally blocked with bovine serum albumin(BSA) to fabricate immunosensor successfully and be utilized to detect CEA. The entire assembly process of immunosensor was characterized by scanning electron microscopy(SEM), electrochemical impedance(EIS) and cyclic voltammetry(CV). Differential pulse voltammetry(DPV) was selected for the detection of CEA. In addition, specificity, reproducibility and stability of immunosensor were also examined. Study of the ability of this immunosensor in practical application was carried out using normal human serum.2. NH3-plasma treated multi-walled carbon nanotubes(pn-MWCNTs) were prepared based onthe plasma polymerization technique and developed as sensing materials for detection of quercetin(Que) and kaempferol(Kae) with the differential pulse voltammetry and amperometric measurement. EIS and CV were used to characterize changes in the electrode surface. Such experimental parameters as p H values, accumulation potential and accumulation time were carefully investigated. The pn-MWCNTs modified electrode(pn-MWCNTs/GCE) was further explored for the analysis of quercetin and kaempferol in diluted blood serum. In addition, the interference and stability measurements were evaluated under the optimized experimental conditions.3. In order to obtain sensitive interface for detecting carbendazim, mesotetra(4-carboxyphenyl)-porphine was grafted onto pn-MWCNT/GCE by EDC/NHS condensation reaction. To characterize modification procedure by two methods including CV and EIS ensure the material reach the electrode surface. Amounts of pn-MWCNTs, the buffer p H and deposition time were optimized in experiment and under optimal conditions, quantitative analysis of carbendazim was achieved by DPV and amperometric technique. The stability and reproducibility on the surface of electrode were research and carbendazim standard solutions were added into the tap water and Huiyuan juice for recovery experiments.Results:1. Under optimal conditions, the immunosensor for detecting CEA in 0.22-34 ng m L-1 showed an excellent linear relationship, the linear equations were ΔI/μA = 38.52 + 10.18 c/μM(R2=0.9965)(0.22-2ng m L-1) and ΔI/μA=57.54 + 0.31c/μM(R2=0.9973)(2-34 ng m L-1), the detection limit was 0.003 ng m L-1. The recovery of CEA in blood serum samples were in the range of 85.5-100.4%.2. By amperometric detection, there were good linear relationship between concentrations of quercetin and kaempferol in the range of 0.05-4.55μM and the corresponding oxidation peak current. The linear equation were Que: I/μA = 0.001+ 0.02c/μM(R2=0.9991) and Kae: I/μA = 0.05 + 0.0196c/μM(R2=0.9902), respectively. The detection limits of both quercetin and kaempferol were 0.05μM. As to the analysis of diluted serum samples containing quercetin and kaempferol, the average recoveries were 96.91(for Que)and 100.5%(for Kae).3. Detected by the I-t curve, the concentrations of CBZ is proportional to the response current on the electrode, the linear equation is I/μA=0.0098+0.03112c/μM(R2=0.9984) at the rangeof 1-11 μM CBZ and the detection limit(LOD) was found to be 0.18μM(S/N=3). As to practical application, the recovery values of four independent experiments varied from 96.3 to 102.8% for tap water and from 95.1 to 104.6% for Huiyuan orange juice.Conclusion:1. The immunosensor based on gold nanoparticles/thionine/amino-functionalized carbon nanotubes(Au NPs/THi/NH2-MWCNTs) is suitable for the detection of CEA because of high specificity, perfect stability and reproducibility.2. pn-MWCNTs modified electrode has been used for selective analysis of quercetin and kaempferol which have similar structures and similar oxidation potential, with to achieve satisfactory results, and it can be used for the actual sample analysis. Simultaneous determination of quercetin and kaempferol in solution and actual samples were successful achieved based on DPV and amperometric measurement.3. The electrode based on meso-tetra(4-carboxyphenyl)porphine/NH3-plasma treated multi-walled carbon nanotubes composite materials has the advantage of good stability and reproducibility, fast detection speed and lower detection limit detection for carbendazim determination. This finding provides a simple, sensitive and reliable method to evaluate carbendazim.