Preparation Of Gold Biomimetic Mineralized Composite Enzyme And Its Preliminary Medical And Environmental Applications

Noble metal nanoclusters especially gold nanoclusters(AuNCs)with excellent size effect and optical and electrochemical functions have been widely used in biological labeling,enzyme catalysis,imaging analysis,and sensing detection.This thesis,on the one hand,has developed the gold-encapsulated glucose oxidase(GOx)complexes based on the biomimetic gold mineralization route.An electrochemical signal amplification technology was thus designed for the ultrasensitive sandwiched detection of DNA sequences of Anthrax virus with the single-base difference in combination with magnetic separation technology.On the other hand,multifunctional enzyme mimic complexes were established based on the hemin-mediated gold biomineralization,showing the peroxidase-like catalysis and catalytic gold silver deposition functions.The obtained hemin-gold complexes were employed to label alpha fetoprotein(AFP)antibody for the rapid,sensitive and visualized detection for human serum AFP.At the same time,the recyclable multifunctional composite materials were synthesized through the combination the hemin-gold complexes and Fe3O4-loaded porous polymer of melamine and formaldehyde resin(mPMF)for the efficient adsorption and catalytic degradation of toxic environmental organic compounds like dyes.The main contents include:(1)An electrochemical sensing technique was developed for the detection of DNA sequence with single nucleotide mutation based on the biomimetic gold mineralization mediated by the protein matrix of GOx(Chapter 2).On the one hand,gold(Au)nanoclusters were synthesized and encapsulated into GOx by the in-site biomimic gold mineralization route with GOx protein as the reducing agent and stabilizer.The resulted GOx-Au composites could show the double catalysis activities of GOx and peroxidase-like catalysis of gold,which could additionally booster the electron transfer of GOx toward the enhanced catalysis for glucose.They were applied to label DNA detection probes with the tyramine modification to work with the magnetic nanoparticles-loaded DNA capture probes that were also modified with tyramine,to conduct the hybridication with the targeting DNAs of Anthrax virus by the sandwiched way.On the other hand,the GOx of GOx-Au catalytzed the hydrolyzation of glucose to produce H2O2 to further spark the oxidative coupling of tyramines catalyzed by the mineralized gold,resulting in the linking of capture and detection DNA probes.A magnetic separation-based sandwiched detection method using GOx-Gold and tyramine labels was thus tailored by the catalytic gold growth for the electroanalysis of DNAs of Anthrax virus in blood with single nucleotide mutation.The developed electroanalysis method breaks through the analysis bottleneck of low-level short chain DNAs,thus providing a new tool for the early diagnosis of clinical anthrax virus infection.(2)Preparation of application of mimetic enzyme complexes based on the hemin-mediated gold mineralization route for the colorimetric analysis of AFP(Chapter 3).The mimetic enzyme complex was formed by the hemin-mediated gold mineralization under the alkaline condition.The obtained hemin-Au composites could not only present the peroxidase catalysis,but also the gold catalysis for the silver deposition reaction.Furthermore,the hemin-Au composites were employed to label the antibodyies of liver cancer markers of AFP by combining with enzyme linked immunosorbent assay.Two rapid and highly sensitive colorimetric detection strategies were developed for probing AFP levels in blood separately through the two kinds of signal amplification ways of peroxidase like-catalyed chromogenic substrate and gold catalyzed silver deposition reactions.(3)Preparation of the catalytic complex materials with magnetic particles-loaded mPMF and hemin-Au composites for the applications of absorption and catalytic degradation of environmental toxins like dyes(Chapter 4).Magnetic Fe3O4 nanoparticles were prepared by the hydrothermal method and loaded with porous mPMF through the hydroxylation reaction.Furhtermore,the resulted magnetic Fe3O4@mPMF complex were coated with the hemin-Au composites by the covalent chemistry to form Fe3O4@mPMF@Hemin-Au materials with the multiple functions of high adsorption surface area,strong catalysis,and recycling usage.The adsorption catalytic degradation performances of Fe3O4@mPMF@Hemin-Au were systematically studied by using two typical dyes of methylene blue(MB)and rhodamine B(RhB)as the examples.The results indicate that the magnetic and catalytic complex materials should be applied widely as green and highly efficient functional materials for the absorption and catalytic degradation of environmental toxins like dyes.