Colormetric Sensing Research Based On Gold Nanoparticles And Dnazyme

There are four chapters in this thesis. A facile, highly sensitive and selective colorimetric strategy for dihydronicotinamide adenine dinucleotide detection is proposed based on anti-aggregation of gold nanoparticles via boronic acid-diol binding chemistry (Chapter2), A simple, highly sensitive and selective colorimetric strategy for phosphate (Pi) detection is proposed based on anti-aggregation of gold nanoparticles (AuNPs) via competition reaction between Pi and carboxylate group-modified AuNPs for Eu3+ions.(Chapter3), A novel, highly selective colorimetric strategy for pyruvic acid detection is proposed based on the effect of concentration of pyruvic acid to ssDNAconformationa and the stability of different ssDNA conformational to AuNPs against salt induced aggregation (Chapter4) and A highly sensitive and selective colorimetric method for coralyne detection has been developed on the basis of a novel catalytic G-Quadruplex DNAzyme oligonucleotide probe(Chapter5).1. The aggregation agent,4-mercaptophenylboronic acid (MPBA), has specific affinity for AuNPs through Au-S interaction, leading to the aggregation of AuNPs by self-dehydration condensation at a certain concentration, which is responsible for a visible color change of AuNPs from wine red to blue. With the addition of NADH, MPBA would prefer reacting with NADH to form stable borate ester via boronic acid-diol binding dependent on the pH and solvent, revealing an obvious color change from blue to red with increasing the concentration of NADH. The anti-aggregation effect of NADH on AuNPs was seen by the naked eye and monitored by UV-vis extinction spectra. The linear range of the colorimetric sensor for NADH is from8.0×10-9M to8.0x10-6M, with a low detection limit of2.0nM.2. A simple, highly sensitive and selective colorimetric strategy for phosphate (Pi) detection is proposed based on anti-aggregation of gold nanoparticles (AuNPs) via competition reaction between Pi and carboxylate group-modified AuNPs for Eu3+ ions.The linear range of the colorimetric sensor for Pi is from5.0×10-7M to3.0×10-8M, with a low detection limit of76nM.3. A simple yet highly selective colorimetric sensing platform for PA was established based on the effect of concentration of pyruvic acid assisted with PDC to ssDN A conformationa and the stability of different ssDN A conformational to AuNPs against salt induced aggregation.. The linear calibration ranged from5.6x10-6M to16.8×10-3M, with a detection limit of3μM.4. A simple label-free colorimetric method for coralyne detection was successfully established based on a novel catalytic G-Quadruplex DNAzyme oligonucleotide probe. Through this method, commonly used steps such as labeling, modification and separation were effectively avoided. So it provided a much simpler, faster, and more economical alternative to traditional methods. The linear calibration ranged from5x10-8M to5×10-6M, with a detection limit of31nM.