The Study Of Molecular Beacon Based Photo-induced Electrochemical Biosensing Method

As the developments of the disease diagnosis, genetic testing, forensics and environmental monitoring, it is more important for the accurate, simple and rapid detection for specific DNA sequences. At present, a series of optical and electrochemical DNA testing technology and sensor has been developed by analysts in order to adapt to the development of life science. This thesis proposed a new biosensing method through combining the molecular beacon, photosensitive reaction and electrochemical reaction;The immobilization of the electrochemiluminescence(ECL) reagent Ru(bpy)32+on the electrode surface by electrodeposition was studied and an ECL sensor was proposed.This thesis has four chapters, the content is as follows:(1)In the first chapter of this thesis, we outlined the structure of the DNA and its conventional methods for the determination of DNA. It was reviewed for molecular beacon and its discipline, the discipline and application of ECL, the discipline of Ru(bpy)32+ECL.(2)Firstly, the requisite electrochemical capture probe of singlet oxygen in the photo-induced electrochemical DNA sensor based on fluorescent molecular marked molecular beacon was investigated. It was studied for the electrochemical response of active oxygen scavenger, such as rutin, dopamine, epinephrine, isoniazid and vitamins C,to the photo-induced active oxygen. It was found that the electrochemical responses of rutin and dopamine to photo-induced active oxygen were more obvious. The type of photosensitive reactions of reactive oxygen species produced was judged. The conditions was optimized, and it was found that, when the p H of phosphate buffer solution was 7, concentration of rutin was 1 ×10-5mol/L and concentration of methylene blue was 1×10-6mol/L, the electrochemical response of rutin to photo-induced active oxygen was most sensitive.( 3) A novel photo-induced electrochemical DNA sensor based on fluorescent molecular marked molecular beacon was developed. In this method the molecular beacon probe labeled with methylene blue and dopamine were first immobilized on the gold nanoparticles modified gold electrode surface. The methylene blue reacted with dissolved oxygen to produce singlet oxygen under illumination, and singlet oxygen could react with dopamine, resulted in the reduction of the amount of dopamine. The electrochemical signal of dopamine was used for the sensing of the conformational change of molecular, and hence for the detection of the target DNA. This method hasbeen successfully used to the detection of cauliflower Mosaic virus genome DNA.(4)A facile and easily controlled method for the fabrication of a silica-based hybrid film and its application as an ECL biosensor were demonstrated. A hybrid silica film containing chitosan, gold nanoparticles, and Ru(bpy)32+was prepared by electrodeposition. The composite film was studied using scanning electron microscopy,electrochemistry and ECL. This ECL analytical performance of the composite film modified electrode was investigated using C2O42-as the model analyte.