Preparation Of Gold Nanorods Composites For Photothermy And Drug Delivery

Cancer becomes a serious global public health issue threatening human life through the ages.Traditional clinical therapies such as chemotherapy,radiotherapy and surgery exhibited serious limitations such as severe side effects and low therapeutic efficiency.[1,2]To circumvent the limitations,for example,burgeoning light-mediated photothermal therapy(PTT)has been developed as a promising alternative therapeutic strategy for tumors.PTT is achieved by the conversion of light into local heat with the help of photothermal transduction agents(PTAs)which can kill tumor cells locally.PTT have several advantages such as high tumor specificity,minimal invasiveness and low systemic toxicity when compared to traditional cancer therapies.PTT under near infrared(NIR)laser irradiation becomes popular because of deeper tissue penetration up to 10 cm and minimal normal tissue invasion due to the minimal absorption by skin and tissue of NIR lightGold nanorods(GNRs),as one of the most studied inorganic PTAs,exhibit two distinct surface plasmon resonance(SPR)peaks due to their anisotropic shapes,namely a weak transverse SPR peak at?520 nm and an intense longitudinal SPR peak spanning from visible to near infrared regions(NIR,650-1200 nm)by adjusting the aspect ratios.The latter SPR peak bestowed on GNRs with excellent photothermal conversion efficiency for PTT and photoacoustic imaging(PAI)capability under NIR laser irradiation.However,the direct use of GNRs in vivo is still restricted due to their potential cytotoxicity from the residual surface surfactants(e.g.CTAB),unsatisfied photothermal stability and aggregation,and the lack of payload holding space.GNRs,for example,would melt into spherical AuNPs under long NIR irradiation due to the low melting point of Au,which weakened their PCE and imaging features due to the shift of absorption peaks away from the wavelength of the laser.This thesis aims to investigate a simple method for the synthesis of three kinds of GNRs composites and to analyze the photothermal therapy and drug release characteristics of it for cancer therapy applications.The main contents of this paper include the following1.The multifunctional GNR@Gd2O3@PDA core/shell nanostructure was prepared by facile step by step route.First,the CTAB capped GNRs were synthesized by seed mediated growth approach,followed by ligand exchange approach to change the surface of the GNR from CTAB to oleate.Next,rare earth oxide(Gd2O3)was grown on oleate-GNRs.Finally,the dopamine molecule was self polymerized onto to the GNR@Gd2O3 surface under alkaline condition with Tris buffer to form a GNR@Gd2O3@PDA core/shell structure.In comparison with GNRs and GNR@Gd2O3@PDA core/shell nanostructure,GNR@Gd2O3@PDA exhibited the improved their photothermal conversion efficiency due to their excellent NIR absorption and photostability.The prepared sample shows the pH and NIR-responsive drug release processes and it can be used as synergetic photothermal and chemotherapy agent for cancer therapy2.A simple synthesis strategy was proposed to fabricate GNR@Gd2O3@SiO2@CaP multifunctional core-shell nanostructures.A mesoporous silica(SiO2)shell was grown on the surface of GNR@Gd2O3 by soft template approach.Then,Ca-PAA self-assembled around the surface of the GNR@Gd2O3@SiO2 upon the addition of isopropanol alcohol(IPA)to obtain GNR@Gd2O3@SiO2@Ca nanostructure.Subsequently,GNR@Gd2O3@SiO2@CaP core-shell nanostructure was formed with the addition of Na2HPO4 as the phosphate anion source.The resulting multifunctional GNR@Gd2O3@SiO2@CaP core/shell nanostructure possesses high drug-loading capacity,pH/NIR dual-responsive drug delivery property and enhanced photothermal efficiency which was applied for chemo-photothermal therapy of cancer cells3.The GNR@SiO2@MnO2 multifunctional nanocomposite was synthesized by a facile preparation method.The SiO2 shell was synthesized using the precursors TEOS and CTAB with template of CTAB-GNRs.The interactions of positive and negative charges of precursors are results in the formation of GNR@SiO2.The mesoporous structure was finally formed by adjusting the amount of CTAB.In order to prevent DOX from leaking from the GNR@SiO2 mesopores,the MnO2 nanosheets were combined with the GNR@SiO2 nanomaterials to form a GNR@SiO2@MnO2 nanocomposite.Among them,the presence of gold nanorods can be used for photothermal therapy;silica SiO2 is a mesoporous structure for drug delivery;MnO2 nanosheets have pH/GSH dual responsiveness and can be used for drug sustained release.Therefore,the synthesized GNR@SiO2@MnO2 nanocomposite is multifunctional,capable of merging the characteristics of each composite nanostructure,and has the ability to release drug and pH/GSH dual-response drug release.