Preparation Of Trypsin-stabilized Gold Nanoclusters For Sensing Of Sulfo-compound

Gold nanoclusters (Au NCs) consisting of a few to a hundred atoms haveemerged as a novel class of the most promising fluorescent labels since they providethe link between atoms and nanoparticles. As the size of Au NCs is comparable to theFermi wavelength of electrons, it has been proven that Au NCs exhibit molecule-likeproperties including discrete electronic state and size-dependent fluorescence,Water-soluble fluorescent Au NCs with color tenability could be synthesized by usingthiols, dendrimer, DNA, protein and others as stabilizer or template. Among theseligands, protein exhibits as biocompatible scaffolds for preparing Au NCs.Protein-ptotected Au NCs has gained much attention due to their goodbiocompatibility, facile preparation, and non-toxicity. Consequently, protein-ptotectedAu NCs show potential as ideal fluorescent materials for advancing fields such asbiosensors, molecular imaging, and nanomedicine. Therefore, the preparation ofprotein-stabilized Au NCs and their application as fluorescent probe is of significantimportance. In this thesis, trypsin was chosen as the model protein for the preparationof protein-ptotected Au NCs. Fluorescent trypsin-stabilized Au NCs (T-Au NCs) werein-situ prepared using protein as both the stabilizing agent and reductant via a rapidultrasound approach. The preparation method was studied. The obtained fluorescentmaterials were characterized by UV-vis absorption spectroscopy (UV-vis),fluorescence spectroscopy, Transmission electron microscopy (TEM), X-rayphotoelectron spectroscopy (XPS), and so on. Meanwhile, the as-prepared Au NCscould be applied in the sensing of sulfo-compound. The detailed results weresummarized as follows:1. Trypsin was used as both a stabilizing agent and a reductant to in-situsynthesize water-soluble fluorescent T-Au NCs with the assistance of ultrasoundmethod. The as-prepared T-Au NCs exhibited red fluorescent emission. Thepreparation process and properties of as-prepared T-Au NCs were investigated using fluorescence spectroscopy, TEM, XPS, UV-vis. The results indicated that thefluorescent T-Au NCs were successfully synthesized, and the valence state of theT-Au NCs was estimated. The fluorescence quantum yield (QYs≈2.2%) wascalculated with rhodamine B as the standard substance. The fluorescence intensity ofT-Au NCs to pH was studied.2. Based on the interaction between T-Au NCs and Na2S through Au-S bond, theeffect of the concentration of Na2S on fluorescence intensity of T-Au NCs was studied.The results showed that Na2S was capable of quenching the fluorescence of T-Au NCs.This phenomenon exhibited sensitive and selective fluorescent response for thedetermination of Na2S. The obtained sensor could detect Na2S with a wide linearrange of0.1-4.0μmol/L and4.0μmol/L-0.7mmol/L.3. Nanomaterials surface energy transfer (NSET) between organic fluorescentdyes-fluorescein isothiocyanate (FITC) and T-Au NCs was constructed to detectsulfo-compound of L-cysteine (CSH). In this system, FITC and T-Au NCs werechosen as the energy donor (a sensitive signal reporter) and acceptor, respectively.Thus, the fluorescence intensity of FITC could be quenched when they were attachedto the surface of T-Au NCs through their isothiocyanate group. Addition of the CSHresulted in the inhibition of NSET, and FITC was released because of the formation ofAu-S bond on the surface of T-Au NCs. As a result, the fluorescence of released FITCmolecules was recovered. The developed sensor demonstrated good performance fordetection of CSH with a wide linear range of50.0pmol/L-10.0μmol/L.