| Nanometer materials have been wildly used for biological molecules hybridizationreaction and specific gene detection because of their unique advantages such as large specificsurface area, high catalytic efficiency and adsorption ability, etc. Compared with theconventional biosensor, the nanometerial-based DNA biosensor presented the fasterhybridization rate, higher hybridization efficiency and better stability. As well known, theimmobilization of single-stranded （ss） DNA probe onto the transducer surface is a crucial stepduring the fabrication of DNA biosensor, which is the important link for improving thestability, reproducibility, regeneration, properties and sensitivity of the biosensor. Thedissertation focuses on selecting several nanocomposites as platform to immobilize the probeDNA through physical absorption or covalent bonding. Main contents are as follows:（1） The bismuth sulfide nanorod （rBi2S3） was first coated on an ionic liquid carbon pasteelectrode （ILCPE）, then the ultrathin film of polyaniline （PANI） polymer waselectropolymerized onto the Bi2S3/ILCPE surface for immobilizing the probe DNA. ThePANI/rBi2S3/ILCPE displayed large specific surface area and high catalytic efficiencybecause of the synergistic effect of the ionic liquid, rBi2S3and PANI. The oligonucleotidesrelated to CaMV35S promoter fragment were determined by electrochemical impedancespectroscopy using [Fe（CN）6]3-/4-as probe with a linear range of1.0×10-151.0×10-11mol/Land a detection limit of4.36×10-16mol/L. This electrochemical DNA biosensor had goodstability, reproductivity, regeneration and specificity.（2） The nanocomposite containing chitosan （CS） and mutiwalled carbon nanotubes（MWNTs） was first coated on a glassy carbon electrode. Then a highly reactive dialdehydereagent of glutaraldehyde （GTD） was applied as an arm linker to covalently graft the5’-amino modified probe DNA to the CS-MWNTs surface via the facile aldehyde-ammoniacondensation reaction. The experimental results showed that the biosensor had wide detectionrange from1.0×10-13to5.0×10-10mol/L and a low detection limit of8.5×10-14mol/L. Inaddition, the hybridization specificity experiments showed that the sensing system can accurately discriminate complementary sequence from mismatch and noncomplementarysequences.（3） The CNT was coated on a glassy carbon electrode and then electropolymerized inthiophene-3-carboxylic acid （TPA） to from a CNT and electropolymerized TPA （pTPA）composite film. Based on the covalent interaction of5’-amino modified probe DNA withcarboxylic acid of pTPA, a DNA biosensor was constructed. Differential pulse voltammetrywas used to the sensitive detection of the hybridization of DNA with methylene blue as theindicator. The oligonucleotides related to CaMV35S promoter fragment were monitored, anda lineare range of1.0×10-17to1.0×10-11mol/L with a detection limit of3.61×10-18mol/L wasobtained. The biosensor also showed good sensitivity, regeneration and specificity.（4） The core-shell structure of Au@Bi2S3was used as a platform for adsorptiveimmobilization of probe DNA to fabricate a novel DNA biosensor. The change of electrontransfer process on the modified electrodes were determined with the developed biosensor viaelectrochemical impedance spectroscopy using [Fe（CN）6]3-/4-as indicating probe with a linearrange of1.0×10-141.0×10-9mol/L and a detection limit of2.0×10-15mol/L. It was alsoshowed that the developed biosensor could display a good selectivity and speediness foranalyzing the target DNA. |
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