Study On Three - Dimensional Ordered Gold - Doped Nanosized Titanium Dioxide For DNA Biosensor

Electrochemical DNA biosensor has been rapidly developed in recent years as a new type of biosensor. It has many advantages of good selectivity, high sensitivity rapid analysis, low cost and easy to be miniaturized.Electrochemical DNA biosensor can accurately detect specific DNA sequence, and has been extensively studied and applied in the field of clinical testing, new drug selecting, environmental monitoring and food engineering.The nanomaterials have opened up new ideas for the development of electrochemical biosensors because of their unique structures and properties. Three-dimensionally ordered macroporous gold-nanoparticle-doped titanium dioxide (3DOM GTD) was prepared by a sol-gel procedure using polystyrene colloidal crystals as templates. The3DOM GTD has large specific surface area, good conductivity special catalytic property and excellent biocompatibility, and can effectively control the fixed orientation of the biomolecules, which are better to maintain the activity of biomolecules.Therefore, this study is of great significance for the development of biosensors with high sensitivity and good selectivity. The main results and conclusions are summarized as follows:1. The preparation and characterization of the3DOM GTD modified electrodeWe fabricated a new3DOM GTD modified electrode by a sol-gel procedure using polystyrene colloidal crystals as templates. The fabrication process was characterized by scanning electron microscopy (SEM) and electrochemical methods. The results indicated that:three-dimensionally ordered macroporous on the surface of the electrode is neat and orderly, the size of the macroporous is uniform. The3DOM GTD modified electrode is an excellent carrier for biomolecules owing to its good biocompatibility and conductivity.2. The3DOM GTD modified electrode was applied to detect the DNA sequence related to the breast cancer geneThe ferrocene-labled DNA was immobilized on the surface of3DOM GTD modified ITO electrode to fabricate a new labeled DNA biosensor which could be used to identify the taeget sequence through the change of the electrochemical signal before and after hybridization.The properties of the DNA biosensor such as the sensitivity, hybridization conditions and stability were studied.The results indicated that the ferrocene on the electrode surface and the target sequence concentration showed a good linear relationship when the concentration of Breast-cancer BRCA1gene ranging from8.0×10-7mol/L～1.0x10-5mol/L,with the detection limit of5.2×10-7mol/L.3. The study of DNA biosensor based on thionine and gold nanoparticles films on3DOM GTD modified electrodeNegatively charged AuNPs were electrodeposited on the3DOM GTD electrode surface,then the positively charged thionine was adsorbed by electrostatic interaction. The ferrocene-labled DNA was immobilized on the thionine and gold nanoparticles films on3DOM GTD modified electrode, resulting a novel DNA biosensor. The properties of the novel DNA biosensor were studied. The results indicated that the ferrocene on the electrode surface and the target sequence concentration showed a good linear relationship when the concentration of Breast-cancer BRCA1gene ranging from6.0×10-7mol/L～1.0×10-5mol/L, with the detection limit of9.7×10-8mol/L.The Th/AuNPs/3DOM GTD electrode can effectively improve the fixation of DNA probes on the electrode surface,and has better stability, reproducibility and electrode regeneration.This biosensor is expected to become a new type of electrochemical DNA biosensor,and applied in the field of DNA hybridization and cancer gene detection.