Study On Targeted Hydrosoluble Gold Nanoclusters And Its Composites Construction For Fluorescence Imaging And Antitumor

Cancer is one of the most serious diseases that threaten human health and life in the twenty-first Century.The early diagnosis and effective treatment of cancer have been the focus of cancer medicine research.On the one hand,fluorescence imaging possesses high sensitivity and resolution at the cell level,which is considered as an effective diagnostic method.On the other hand,photodynamic therapy(PDT)and photothermal therapy(PTT)are both minimally invasive cancer therapies.Compared with other traditional tumor therapies,such as chemotherapy and radiotherapy,PDT and PTT show little side effects,high selectivity and low treatment cost.Therefore,the development of functional nanomaterials with excellent biocompatibility,targeting,optical properties and therapeutic effect to realize imaging diagnosis and treatment of tumor cells is the direction we need to strive.Compared with traditional organic dyes,water-soluble gold nanoclusters(AuNCs)have become a new generation of diagnostic and therapeutic agents because of their excellent biocompatibility,low toxicity,ultra-small particle size and strong fluorescence.Our main works are aimed at the direction of this frontier research and carried out around the hydrosoluble AuNCs,and the obtained results can be summarized as follows:1.We synthesized a kind of water-soluble AuNCs protected by glutathione(GSH)with high fluorescence through one-step method,which could changed into another kind of AuNCs.protected by dual mitochondrial targeting ligand molecule((4-mercaptobutyl)-triphenylphosphonium bromide,MTPB)and GSH through ligand exchange.The nuclear magnetic hydrogen spectrum(1H NMR)and electrospray ionization mass spectrometry(ESI-MS)tests showed that the molecular formulas of the two nanoclusters were Au18SG14 and Au18SG12MTPB2,respectively.The synthesized Au18SG14 can concentrate in lysosomes,whereas the ligand exchanged Au18SG12MTPB2 gives rise to a target switching,that is,targeting mitochondria instead of lysosomes.From the test of the generation of 1O2,both two kind of nanoclusters could obviously induce the generation of 1O2 under the irradiation of 638nm laser.However,the poor photodynamic effects of Au18SG12MTPB2 nanoclusters were observed compared with Au18SG14nanoclusters,may be due to the exchange of two-SG ligands.We also demonstrate that Au18SG12MTPB2 with less 1O2 generation efficiency,but exhibits identical cytotoxicity toward cancer cells as that of Au18SG14,indicating the more significant photodynamic activity in mitochondria on cell death than that in the lysosome site.2.We first prepared a kind of mesoporous silica nanoparticles with special two-tiered mesoporous structure(TMS),after modified by amino group,the as-prepared AuNCs was loaded in the mesoporous channel of TMS via electrostatic adsorption.Then,the prepared AuNCs@TMS was gated by gelatin/folic acid(FA)through amidation reaction to obtain the final products(AuNCs@GTMS-FA),which could conquer the poor stability of hydrosoluble AuNCs.The fluorescence spectrum analysis showed that the fluorescence intensity of AuNCs@GTMS-FA was also increased compared with the only AuNCs,which was 3.3 times as much as that of AuNCs.The AuNCs@GTMS-FA nanocomposites not only exhibited excellent photodynamic effect,but also a certain ability of transforming light to heat under a laser irradiation.After a 808nm laser for 9min,the temperature of AuNCs@GTMS-FA dispersions can rise from 22.6 ℃ to 43.7℃.The cell cytotoxicity experiments indicated that AuNCs@GTMS-FA nanocomposites exhibited commendable biocompatibility,which could specifically targeted to cancer cells and kill cancer cells through the synergistic effect of PDT/PTT while the side effects to normal cells could be reduced.The confocal fluorescence imaging experiment showed that the AuNCs@GTMS-FA nanocomposites presented a better fluorescence stability than discrete AuNCs inside the cells,thus we can conclude that AuNCs@GTMS-FA nanocomposites show a better fluorescence imaging ability.3.We attempted to develop an enzyme-response hyaluronic acid(HA)/GSH stabilized AuNCs-graphene oxide(GO)complex(HG-AuNCs/GO)as a novel theranostic platform.Multifunctional fluorescent and photosensitive HG-AuNCs have been firstly prepared in situ with HG as a protective layer,which could be specifically targeted to the activated CD44 receptor on the surface of cancer cells.The assembly of HG-AuNCs and GO gave the HG-AuNCs/GO complex,a turn-on theranostic platform with strong inhibition of both fluorescence and 1O2 generation by GO,which could also effectively restored under the enzymolysis stimulation of lysosomal hyaluronidase.The confocal fluorescence imaging assay showed that the surface of different cancer cells presented different expression levels of CD44.In addition,A549 cells co-incubated with HG-AuNCs/GO complex had the best fluorescence imaging effect due to the superior CD44 expression level.The cell cytotoxicity and dead/live cells dual-staining experiments indicated that the enhanced therapeutic strategies associated with dual PTT/PDT can be realized by the combination of HG-AuNCs with GO.