| Firstly an amperometric immunosensor with enhanced sensitivity was successfully developedby co-immobilizing multi-walled carbon nanotubes(MWCNTs), Chitosan(CS), HRP labledpenicillin antibody (HRP-Ab) on glassy carbon electrode using a layer-by-layer assemblytechnique. HRP can catalytic the reduction of H2O2to promote the oxidation of hydroquinone,causing the changes in impedance, then realizing the quantitative detection of penicillin(PEN)according to that. The MWCNTs-CS film,which offered a large specific surface forimmobolilization of penillin antibodies, showed excellent biocompatibility, high stability and goodconductivity. Based on that，then we improved the detection limits and prepared a newlynanotubes-magnetic immune bio-probes for detection of penillin in food by synthesizing somemagetic nanocomposites, which were used to lable the antibody. The bio-probes can selectivelyseparate and enrich the antigen,and the obtained immuno-magnetic beads were immobilized on thesurface of modified GCE. After determination, the GCE can be regeneration by romoving themagnet，which constructed a renewable amperometric immunosensor with higher sensitivity, lowerdetection limits for the detection of penillin in food. Details are as follows:1.We studied the synthetic of multi-walled carbon nanotubes-chitosan composite sensors(MWCNTs-CS) and the characterization of related substances, we constrcted the impedanceimmuno-sensors (GCE-MWCNTs-CS-Ab) by layer-by-layer technique: First the MWCNTs, whichwere carboxyed, was electrodeposited on GCE, then the positively charged chitosan (CS) wasadsorbed afterwards, finally the negatively charged Ab was adsorpted on the surface ofMWCNTs-CS film firmly. the morphologies of MWCNTs、MWCNTs-CS、MWCNTs-CS-Ab wasinvestigates by SEM, it was found that the composites can meet the requirements. Meanwhile, weapplied the imune sensor to detecte penicillin in milk, the results shows: Under optimizedconditions, the current response of the sensor showed a good linear relationship with theconcentration of penicillin in0.05~5.00μg L-1, with the correlation coefficient of0.9853and thedetection limit was1.05μg L-1. Finally, This method was fast, simple and reliable, with highsensitivity, specificity compared to enzyme-linked immunosorbent assay (ELISA), It was proved tobe used to detect penicillin residues in milk samples.2. A newly electrochemical immunosensor for penillin detection based on MWCNTs andFe3O4/Au nanoprobes was developed in this study. Firstly, the carboxylated MWCNTs wasprepared and adsorbeded on the surface of modified GCE to prepare the basicelectrode(GCE/MWCNTs). Secondly, horseradish perxidase(HRP) labled PEN-Ab (HRP-Ab) and bovine serum albumin(BSA) were sesembled on Fe3O4/Au. Finally the Fe3O4/Au-HRP-Ab wereintrocuced on the surface of GCE by external magnet to preparebiosensor(Fe3O4/Au-HRP-Ab-MWCNTs-GCE). The mount of penillin in the target analyte, whichcould combine the penillin antibody modified on GCE to form immune-complexes, wasdetermined by one-step immunoassay. The higher penillin concentration in the target system, themore immune-complexes it produced. The more immune-complexes would hinder the electrontransfer on the surface of GCE, the redox peak currents decreased afterwards. Therefore, thequantitative determination methods of penicillin can be achieved. the results showed the currentresponse of the sensor showed a good linear relationship with the logarithmic of penicillinconcentration in milk in0.005~50.00μg L-1, with the correlation coefficient of0.9985and thedetection limit was0.1050μg L-1, the detection limit of sensor is higher10times than the sensor(GCE-MWCNTs-CS-Ab)we achieved in the chapter3, showed that the sensor has moreadvantages and application values over that (GCE-MWCNTs-CS-Ab) in the chapter3.Furthermore, the sensor sets separation, enrichment, determination as one, both with goodreproducible、strong reliability、simple making and easy to update, making it more suitable for thetrace detection of penicillin. |
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