Groping Investigation For A New Type Of Electrochemical DNA Biosensor Based On Ldhnanosheets

In the investigation of DNA biosensors, immobilization of DNA is a key, since the improvement of which can decrease the steps of immobilization, abate the varieties of chemical used in the immobilization and make the DNA biosensors more sensitive. As the result, the immobilization of DNA is a very important factor of DNA biosensors' performance and applications.Co-Al-LDHNS, with high surface area and good electrochemistry ability, used to modify the electrode, can largely improve DNA immobilization, electrical responses and the detection sensitivity. Therefore, a DNA/LDHNS modified electrode as an electrochemical biosensor used the Methylene blue (MB) as the indicator was fabricated by instillation drying method in this thesis. It contains two parts as follows:1. The LDHNS were applied to immobilize DNA on the glassy carbon electrode (GCE). Cyclic voltammetry was used to characterize the electrochemical performance of DNA/LDHNS/GCE in 20μmol·L^-1 MB-50 mmol·L^-1 Tris-HCl buffer solution. DNA/LDHNS/GCE was applied to detect phenol with the concentration in the linear range of 4-20μmol·L^-1, and the detect limit was 5 nmol·L^-1. In the present of equal concentration of interferent with phenol, such as phenolic compound, aniline and inorganic salt, their interferential percent were all below 5%. The reproducibility of CV measurement of phenol was estimated to be 1.2% of relative standard deviation (R. S. D. %), and the signal of CV peak current remained 92% one month later, and 59% ten months later.2. LDHNS were also applied in the immobilization of DNA as a modified film on indium tin oxide (ITO) electrode. UV-vis absorbance spectra showed that DNA immobilized firmly and retained its inherent structure in the film. Cyclic voltammetry was used to characterize the electrochemical performance of DNA/LDHNS/ITO in the 50 mmol·L^-1 Tris-HCl buffer solution and 20μmol·L^-1 MB-50 mmol·L^-1 Tris-HCl buffer solution, and differential pulse voltammetry was used to characterize the electrochemical performance of DNA/LDHNS/ITO in the 20μmol·L^-1 MB-50 mmol·L^-1 Tris-HCl buffer solution. DNA/LDHNS/ITO was applied to detect phenol in the 20μmol·L^-1 MB-50 mmol·L^-1 Tris-HCl buffer solution with the concentration in the linear range of 8-48μmol·L^-1 it was also used to detect tetramethyl ammonium hydroxide (TMA) with the concentration in the range of 0-200μmol·L^-1. DNA/LDHNS/ITO utilized no-covalent action between phenol and DNA to detect phenol, and alkylation between TMA and DNA to detect TMA. The reproducibility of DNA/LDHNS/ITO was estimated to be 3.6% of relative standard deviation (R. S. D. %), and the signal of CV peak current remained 65% five months later.