Synthesis And Biomedical Application Of Metal Based Nanomaterials

Metal based nanomaterials have attracted a lot of attentions due to their small size,good biocompatibility and antibacterial property.Due to these advantages,they have been exploited in applications like drug/gene delivery,sensing,imaging,cancer therapy and antibacterial application.However,there are still many difficulties to concur regarding their biosafety and other biomedical application.The present work is mainly focused on the design and preparation of a variety of metal based nanomaterials and their applications in photothermal therapy,radiation enhancement therapy and biosafety.The present work can be summarized as follows:（1）Synthesis and Characterization of PEGylated Au@Pt nanodendrites（Au@Pt NDs）.The multifunctional Au@Pt NDs were prepared via reduction of Pt（acac）₂ on the surface of Au nanocore in oleylamine（OAm）under hydrogen atmosphere.After Pt（acac）₂ was added,Pt metal nanobranches grew on the Au nanocore surface,which led to the hybrid core–branches bimetallic NDs.Lipoic acid terminated PEG was finally grafted to impart water-solubility and biocompatibility.The chemical compositions and morphology of Au@Pt NDs have been fully characterized by TEM,Energy dispersive spectroscopic（EDS）,¹H NMR,UV-Vis,DLS and ICP-MS.（2）Study of PEGylated Au@Pt nanodendrites（NDs）as a novel X-ray computed tomography（CT）and PTT/RT enhanced theranostic agent for cancer therapy.The absorption of Au@Pt NDs was turned to the near-infrared region with the growth of Pt nanobranchesand thus enhances the efficacy of PTT.Furthermore,because of the high atomic number（high Z）of Au as well as Pt,Au@Pt NDs significantly enhanced lethal effects of RT by inducing a highly localized radiation dose within cancer cells.More importantly,the combination of Au@Pt ND-enhanced RT with PTT suppressed cancer cell growth more efficiently than that of RT or PTT alone,indicating a synergistic effect.Meanwhile,the Au@Pt NDs also possess significant CT imaging signal enhancement that has the potential to guide PTT/RT for cancers.（3）Synthesis of PEGylated ferrocene nanoconjugates as the radiosensitizer of Cancer Cells.A new type of radiation sensitizer（Fc-PEG）was synthesised by a facile one-step reaction of conjugating the hydrophilic PEG chain with hydrophobic ferrocene molecule.The chemical composition and structure of Fc-PEG have been thoroughly characterized by FT-IR,NMR,GPC,and MALDI-TOF mass spectrometry.This Fc-PEG conjugate could self-assemble in aqueous solution into spherical aggregates.After the chemically bonding with PEG chains,the uptake level of Fe element could be enhanced via the formation of aggregates.The live/dead,CCK-8 as well as apoptosis assays indicated that the death of cancer cells can be obviously increased by X-ray radiation after the incubation of these Fc-based nanoconjugates,which might be served as the radiation sensitizer towards cancer cells.（4）Synthysis and antibacterial activity of Mo S₂ nanosheets.The Mo S₂ nanosheets were prepared by surfactant exfoliation method and inspected by AFM and SEM.In this study,we investigated the antibacterial activity of Mo S₂ nanosheets against a Gram-negative Escherichia coli（E.coli）and Gram-positive Staphylococcus aureus（S.aureus）by the method of colony-forming units（CFU）.To better understanding the antibacterial mechanisms of Mo S₂ nanosheets,reactive oxygen species（ROS）generation was analyzed by an oxidant-sensitive DCFH-DA probe and morphological changes were detected by scanning electron microscope（SEM）.Cytotoxicity to eukaryotic cells was evaluated by CCK-8 assay.On the basis of those data,we have revealed that Mo S₂ nanosheets were toxic to grem-positive and Gram-negative bacterial strains,however,less toxic to eukaryotic cells.The antibacterial activity of Mo S₂ nanosheets may attribute to both the generation of ROS and directly injury membrane of bacterium.（5）Synthysis and antibacterial activity of WS₂ nanosheets.The WS₂ nanosheets were prepared by surfactant exfoliation method and inspected by AFM and SEM.In this study,we investigated the antibacterial activity of WS₂ nanosheets against a Gram-negative Escherichia coli（E.coli）and Gram-positive Staphylococcus aureus（S.aureus）by the method of colony-forming units（CFU）.To better understanding the antibacterial mechanisms of WS₂ nanosheets,reactive oxygen species（ROS）generation was analyzed by an oxidant-sensitive DCFH-DA probe and morphological changes were detected by scanning electron microscope（SEM）.Cytotoxicity to eukaryotic cells was evaluated by CCK-8 assay.On the basis of those data,we have revealed that WS₂ nanosheets were toxic to grem-positive and Gram-negative bacterial strains,however,less toxic to eukaryotic cells.The antibacterial activity of WS₂ nanosheets may attribute to injury membrane of bacterium instead of the generation of ROS.