Preparation And Biological Application Of Gold Nanocluster/Polymer Composite Nanoprobes

Gold nanoclusters(Au NCs) generally constitute several to dozens of gold atoms which play the core role. The ligands are organic molecules such as thiol compounds, proteins and so on. Ligands and metal core atoms self-assembles into molecular aggregations. As new nanometer materials, Au NCs possess size of subnanometer dimensions, discrete energy levels and tunable size-dependent in the visible region when they compare to nanoparticles. In addition, Au NCs have good biocompatibility, good water solubility and other excel ent features. The superior properties of Au NCs have established their enormous application potential in biosensing, bioimaging, photodynamic therapy, and drug delivery.With a simple and “green” synthetic strategy, the preparation of BSA-Au NCs are based on the ligand of bovine serum albumin(BSA). BSA-Au NCs possess charming properties, such as small size, high fluorescence quantum yield, good stability and biocompatibility, and so on. BSA-Au NCs have been developed for biosensing, bio-detecting and clinical diagnostics applications. However, the relative small significantly limits BSA-Au NCs’ application in cellular labeling. In this paper, we designed the gold nanocluster/polymer composite nanoprobes which exhibited optical properties of BSA-Au NCs and size of suitable for cellular labeling.We firstly used BSA and chloroauric acid to form ~ 1 nm BSA-Au NCs. Then the gold nanocluster/polymer composites materials were achieved with the reactions between P4VP(Poly(4- vinylpyridine)) and BSA-Au NCs. In the second chapter, we prepared three different size(20 nm, 40 nm, 100 nm) of composite materials via changing the P4 VP reaction-concentration. The features of composite nanomaterials such as size, zeta potential, spectra, morphology and fluorescence brightness were characterized. The gold nanocluster/polymer composites possess spherical shape, similar optical properties of BSA-Au NCs, good colloidal stability, size of suitable for cellular labeling. The gold nanocluster/polymer composites have certain application potential in cel ular imaging due of the above advantages.In the third chapter, we carried out the cellular toxicity and cellular labeling experiments of the gold nanocluster/polymer composite nanoprobes. The MTT assay results indicated that the 100 nm gold nanocluster/polymer composites had minimum cytotoxicity under the conditions of various concentrations.We also observed that these three materials had very low cytotoxicity at lower concentrations(50 μg/ml, 100 μg/ml) and cytotoxicity of the 20 nm gold nanocluster/polymer composites increased apparently at higher concentrations(200 μg/ml). Herein, we made a conclusion that gold nanocluster/polymer composites had good biocompatibility and low cytotoxicity. In the fluorescence labeling of MCF-7 human breast cancer cells experiments, we evaluated the cel ular labeling efficiency of three materials by analyzing fluorescence images. Then the optimal composites’ size for cel ular labeling were selected. The cel ular labeling results indicated that the larger size(40 nm, 100 nm) gold nanocluster/polymer composites exhibited stronger fluorescence and higher efficiency upon photoexcitation. Hence, we chose gold nanocluster/polymer composites with a diameter range of 40- 100 nm, having analyzed the above experimental results.