| Recent years, nanotechnology has been developed very well in the electrochem- istry biosensor. Nanomaterials have attracted more and more interesting because of the special properties in physics and chemistry, especially, some oxide nanoparticles attract more attentions with the accelerating electron transfer and the better biocom- patibility. In this work, the nanomaterials and composite nanomaterials are used to constr- uct the electrochemisty biosensors by means of the combination of nanomat- erials, mixture dipping or self-assembly methods. Three methods are investigated to construct interface for immobilize Hemoglobin (Hb) biosensor.(1) In the chapter 2, composite film is formed by combining Nano ZnO with chitosan (CHIT) dispersed solution and gold nanoparticles (GNPs), immobilizing Hb. The ZnO-CHIT dispersed solution with its better biocompatibility providing biological environment for Hb. The composite film can provide conductive channel and reduce the distance between the electrode and the active centre of Hb, achieving direct electrochemistry of Hb. UV-VIS Spectrophotometer and Transmission electron microscope (TEM) are used to characterize the forming process of the composite film. The result shows that Hb contains its own bioactivity with the help of the composite film. The modified electrode exhibits a good catalytic activity towards the reduction of H2O2. The responses of H2O2 are linearly proportional to the concentration from 1.94×10-7～1.73×10-3 M with a detection limit of 9.7×10-8 M (S/N = 3). The relative standard deviation (R.S.D.) was about 2.3% for as-prepared electrodes in 0.2 mM H2O2 in 0.05 M PBS (pH 7.0), exhibiting the proposed biosensor possessed a good reproducibility and stability. The proposed method can immobilized other proteins or enzymes.(2) In the previous chapter, the humidity and the temperature influence the preparation of the modified electrode, and high amount of Hb is required. Hereby, in this chapter, we try to Layer-by-Layer self-assemble poly (dimethyl diallyl) ammonium chloride (PDDA), GNPs and ZnO-CHIT mixed Hb in three steps though the electrostatic interaction. As well known, the GNPs can be acted as the conductive channel, which is confirmed by cyclic voltammetry and impedance. We find that the better biocompatibility of ZnO-CHIT dispered solution can keep the electroactivity of Hb by UV-VIS Spectrophotometer. The direct electron transfer between the Hb and modified electrode, exhibiting a good catalytic activity towards the reduction of H2O2. And the modified electrode of PDDA/Au/(ZnO-CHIT-Hb) responsing of are linearly proportional to the concentration H2O2 from 6.57×10-7 to 1.3×10-3 M with a detection limit of 7.89×10-7 M (S/N = 3). R.S.D. was about 2.0% for as-prepared electrodes in 0.2 mM H2O2 in 0.05 M PBS (pH 7.0).It exhibits that the proposed biosensor possessed a good reproducibility and stability, which is better than that of the dipping method.(3) In the chapter 3, the problem we meet is that the polymer of PDDA lead GNPs to aggregation for damaging the bioactivity of Hb. In addition, the prepared process is too complicate. In the chapter 4, we try a simpler method that the ZnO NPs are mixed with Hb by reciprocity because of the otherness of isoelectric point between ZnO NPs and Hb, and then self-assemble them on the cleaned glassy carbon electrode (GCE). The direct electron transfer is realized between the modified electrode and Hb. UV-VIS Spectrophotometer, TEM and cyclic voltammetry are used to characterize the process of the as-prepared electrode. The responses of H2O2 are linearly proportional to the concentration from 1.06×10-6～7.82×10-3 M with a detection limit of 8.86×10-7 M (S/N = 3). R.S.D.was about 1.9% for as-prepared electrodes in 0.15 mM H2O2 in 0.05 M PBS (pH 7.0). This method exhibits the facile-made and a good reproducibility and stability of biosensor. |
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