Electrochemical Biosensors Based On Gold Nanoparticles And Restriction Endonuclease

Gold nanoparticles have attracted increasing attention in electrochemical biosesors field because of easy synthesis and modification, good stability and excellent biocompatibility. In addition, the high loadage of nanoparticles has been successfully used for signal amplification. Meanwhile, restriction endonuclease has attracted intensive attention in electrochemical biosensors field because of specific recognition of DNA sequences and efficient catalyzation, which could enhance the signal of detection through flexible design. In this thesis, simple, sensitive electrochemical biosensors were demonstrated based on gold nanoparticles and the restriction endonuclease amplification strategies. The main researches are summarized as follows:1. An electrochemical biosensor for melamine detection based on gold nanoparticles signal amplification strategiesMelamine could form triple H-bonds with thymine in aqueous medium. An electrochemical biosensor for melamine detection based on DNA modified gold nanoparticles amplification strategies was demonstrated. In this system, the T-rich DNA probes were immobilized on electrode surface as recognition element. The cationic electroactive complex [Ru(NH3)6]3+ was bound to the DNA via electrostatic interactions as signal molecules. Since hundreds of DNA molecules were loaded on single gold nanoparticle, a good specificity and sensitivity was obtained in this method, the detection limit was ca. 0.5 nM.2. An electrochemical DNA biosensor based on restriction endonuclease amplification strategiesRestriction endonuclease could recognize a specific sequence of double-stranded DNA, and then nick at the recognition site. An electrochemical DNA sensor was demonstrated based on surface adjacent hybridization reaction and restriction endonuclease amplification strategies. The strand-specific restriction endonuclease was employed in this DNA sensor to digest double-stranded, which in turn release the target DNA. Therefore, each target DNA strand could go through many cycles, resulting dramatically signal change. The detection limit was ca. 14 pM. Furthermore, the system could discriminate the complementary sequence from mismatch sequences with high sensitivity and stability.3. An electrochemical biosensors for recognition of single-base mismatch DNA based on surface ligation reaction and gold nanoparticlesThe DNA ligase could offer high accuracy for single-base mismatch recognition. An electrochemical biosensor for single-base mismatch recognition was demonstrated based on surface ligation reaction and DNA modified gold nanoparticles. The biosensor had shown a successful application in sensitivity DNA sensing with high discrimination capacity of single-base mismatch, with a detection limit of 0.9 pM for complementary DNA (cDNA). For single-base mismatched DNA (smDNA), a negligible signal was observed. Even the concentration ratio of cDNA to smDNA was decreased to 1:1000, a detectable signal was observed.