Fabrication Of Branched Au Nanoparticles/Polymer Composites For Tumor Cell Photothermal Therapy

Nobel metal nanostructures due to their catalytic, optics, electronics, biology, surface-enhanced Raman scattering(SERS) and other fields have been become the focus and hotspot in the nanotechnology research. Nobel metal nanoparticles(NPs), especially Au NPs with different size and morphology will show differernt optical absorbance spectrum. Due to the high cross section area of Au NPs, they can transmitte the absorbed light into heat in picosecend. The photothermal therapy using Au NPs as photothermal agents has been explored in recent years. With the development of the photothermal therapy, the nanomaterial based on Au element with a variety of size, shape, composition and morphology has been gradually synthesized. What’s more, the bimetallic nanosturtures also been explored to get better photothermal transmit efficiency. In order to be applied in the phototheral ablation of cancer cells, the NPs need to modify the functional biomolecula with the special design. Among the surface functionzation strategies, the polymer coating is a excellent choice for improving the structure stability, biocompatibility of the anisotropic Au nanostructure. Addtionally, by fabrication the platform of the Au NPs with polymer shell nanostructures, it can further realize the target recognition, anti-cancer drug loading and controlled release, biological imaging and the diagnosis and treatment of disease.In the chapter 2, we utilized seed mediated method and chose hydroquinone(HQ) as reductant to synthesize the urchin-like Au NPs. By altering the amount of HAu Cl4, Au seeds and hydroquinone, the size of the urchin-like NPs were tunable from 55 to 200 nm. The increase of the hydroquinone concentration promoted a kinetics-favored deposition of gold atoms on the(111) lattice planes and thereby the growth of branches. In order to improve the sturctural stability and biocompatibility of the urchin-like NPs, the biocompatible polypyrrole(PPy) were chosen as the shell material for coating the as-prepared NPs via in situ polymerization. The systematic experiment results indicated that PPy-coated NPs exhibit improved structural stability toward storage, heat, p H, and laser irradiation. In addition, the thin shell of PPy also enhances the photothermal transduction efficiency of PPy-coated Au NPs.In chapter 3, we we report an extended galvanic replacement for preparing branched Au-Ag NPs using Ag seeds as sacrifice template. The galvanic replacement reaction is generated because the standardreduction potential of AuIII/Au0(1.003 V vs SHE) is higher than that of AgI/Ag0(0.799 V vs SHE). As a result, Ag seeds are etched and oxidized into AgI ions. Meanwhile, AuIII is reduced into Au0 and deposits on the residual Ag seeds. Subsequently, HQ is used to reduce excessive AuIII and the released AgI ions, successively. The deposition of them on the seeds supplies the further growth of branched structures. According to the element analysis and mapping, the growth mechanism was further investigated. By altering the feed ratio of Ag seed, HAu Cl4 and HQ, the size and absorption spectrum of the NPs were tunable. Therewith, we chose polydopamine with excellent adhesion ability as the shell material to coat the branched Au-Ag NPs. In comparison with bare NPs, PDA-coated branched Au-Ag(Au-Ag@PDA) NPs exhibit improved stability, biocompatibility, and photothermal performance. For the Au-Ag@PDA NPs with 10 nm PDA shell thickness, the photothermal transduction efficiency is calculated to be 61.4%. Utilizing the catechol on the PDA can conjugate with the SH- and NHterminal biomolecular will promote the application in selective treatment of tumor cells. Upon the 808 nm lase irradiation, The Hela cell viability decreases to 9% as the concentration of Au-Ag@PDA NPs at 40 μg/m L.In chapter 4, we chose polyol acted as both reductant and stbilizer, to achieve the synthesis the core-shell composite NPs in one step. By altering the reaction agents, the plasmon resonance absorption of the synthesized NPs were tuned to near-infrared(NIR) region, making them as potential materials in photothermal therapy. Dopamine contained both catechol and amine groups, which can act as reductant to redue the Au and Ag precursor to form hollow Au-Ag bimetallic NPs. And then, by altering the growth solution into alkaline environment, the residual dopamine will spontaneously polymerize on the surface of the hollow Au-Ag bimetallic NPs to form a coating layer. The one step strategy effectively avoided the large loss of as-prepared NPs in the purification and centrifugation. And the core-shell NPs synthesized by this method exhibited a better mophplogy stability. At last, the as-prepared Au-Au-PDA NPs with the SPR peak at 800 nm were applied into the photothemal ablation of thyroid cancer and achive abvious inhibiting effect. In addition, catechin was a kind of water soluble polyol extracted from tea. Due to the hydroxyl in the catechin, it possessed an amaizing reducing ability. After the reaction between HAu Cl4 and Ag seeds, the amount of catechin will effect the morphology of the formed NPs. When the volumn of catechin is less than 100 μL, the NPs were ultraspindly branched nanostructure, and the SPR peak can reach 1200 nm. When the volumn of catechin is more than 300 μL, the NPs were core-shell nanostructure, with the branch Au-Ag core and poly-catechine shell. And the poly-catechin shell thichness will enhanced with the volume of catechin. The interesting growth mechanism were under research. And we plan to apply the ultraspindly branchend NPs in the photothermal therapy under the window II(1000-1350 nm).