| Carbon nanotubes (CNTs) have become a focus of physical, chemical, material and even biological fields, due to their unique electronic and mechanical properties since their discovery in 1991.With the development of research work,nanomaterials are used widely as a new biosensor materials for electrodes modified by chemical methods and applied as biosensor. Due to their unique one-dimenoion structures, CNTs have excellent electrochemical properties that are useful for electrochemical studies and electroanalytical application, electrocatalysis and electrochemical sensors , which provides a wider prospect.As chemically modified electrodes or the materials of sensors, CNTs not only have many advantages of nanomaterials, but also the large specific surface area , high surface activity , more functional groups of the surface and a good bio-affinity. With the increasing of bioactive molecules immobilized on carbon nanotube, the response signal, reproducibility, detection limit and sensitivity of the modified electrodes also highly enhanced. These characteristics of carbon nanotube for the improving performance have great significance. For the application of carbon nanotube on the biochemistry and the biological electroanalytical chemistry, CNTs must have the biospecific interaction with biomolecules, especially, the recognition of biomolecules. Thus, the CNTs are functionalized by the biomolecules to posses a good bio-affinity and the recognition function.This paper presents the research on the basis of carbon nanotubes functionalized by biomolecules, such as enzyme, protein,amino acid , peptide, deoxyribonucleic acid and antigen/antibody at home and abroad. Covalent functionalization of carbon nanotubes(CNTs) with DNA has been successfully achieved via forming covalent amide bonds between carboxyl groups of the nanotubes and amino groups at the ends of the DNA oligonucleotides. The morphology and the structure of carboxylic CNTs and CNTs covalently functionalized by DNA were examined by FT-IR spectra, AFM and field emission scanning electron microscope (SEM). Electrochemical characteristics of the DNA functionalized CNTs and the interaction between DNA and RF (Riboflavin) has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Differential Pulse Voltammetry (DPV). The results showed that DNA retaining its bioactivity is covalently immobilized on the surfaces of CNTs and still has the ability to interact with other biomolecules. RF can be detected obviously by the preparation of DNA covalently functionalized CNTs electrodes (DNA/MWNTs). The linear ranges of the concentrations of RF were of 5.0×10-6～3.0×10-5 mol/L and the detection limits of RF was 1.43×10-6 mol/LThe interactions of DNA immobilized on the DNA/MWNTs electrodes with methylene blue (MB) were investigated by means of electrochemistry. The electrochemical behavior of the MB on the surface of the DNA/MWNTs electrodes was investigated in detail. The scan rate, pH value, the ionic strength, and the concentration of MB were studied for their effect on the electrochemical performance of MB on the DNA/MWNTs electrodes. The conditions of DNA interaction with MB were also optimized. The results show that the redox currents of MB at DNA /MWNTs electrode had linear relationship with scan rate from 20 to 200 mV?s-1, as expected for an absorption control process. The anodic and cathodic peak potentials both shifted negatively with increasing pH from 65.1mV to 7.1mV. The optimal ionic concentration of NaCl is about 25.0 mmol/L. It can be found that the peak current of MB increases with the increasing of concentration of MB. The peak currents have already tended to be stable while the concentration of MB reaches 1×10-4mol/L. The foundation of DNA/MWNTs electrodes was applied to the study on the interactions of DNA with MB which was used as the hybridization indicators was established. |
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