Silica Sufrace Modification And Biocompaitbility Of Gold Nanorods

Noble metal nanoparticles have been the focus of intensive research due to theirunique properties. Different methods of preparing noble metals were studied by manyresearchers, and their size-and shape-dependent properties were also investigated, inthese noble metal nanoparticles,gold nanorods got more attentions. GNRs areelongated gold nanoparticles with unique optical properties depending on their size andshape, GNRs possess two absorption bands, longitudinal plasmon band and transverseplasmon band, the longitudinal plasmon band is tuable, with the increase of ratio oflength to width, the longitudinal plasmon band located from visible region to thenear-infrared (NIR) region. Based on this, there are many exciting applications forphotothermal therapy, optical imaging, and biosensing.Now there are many methods tosynthesize gold nanorods,such as porous aluminum template method,electrochemicalmethod, photochemical method, and the seed-mediated growth method, of all thesemethods, the seed-mediated growth method is widely used. Generally, theseed-mediated growth method includes two steps: synthesis of seeds and the growth ofseeds. The former is done by using a strong reducing agent to reduce a metal saltsolution in aqueous medium so as to get a certain size of spherical gold nanoparticles,After the gold seeds are formed, the next step is to add them into the surfactant, whichacts as a soft template to direct seed growth. To obtain a high yield of GNRs, CTAB,an important cationic surfactant, is frequently used, which acts not only as an inducingagent but also a capping agent to ensure the structure of gold nanorods. The CTABmolecule has a long alkyl chain, which makes it difficult to further modify GNRs inthe presence of abundant CTAB, at the same time CTAB have high toxicity. However,removing excess CTAB will cause GNRs to undergo irreversible aggregation, Therefore, it is imperative to implement surface modifications before further biologicalapplications. So in this paper, gold nanorods were synthesized by seed-mediatedgrowth method and coated with CTAB molecules first, the CTAB molecules were thenreplaced with silica by improved St¨obe method. Cytotoxicity of the silica-coatedgold nanorods were assessed by cell proliferation assay with CCK-8detection. In thepaper we have done the following work:1.Using seed-mediated growth method to getgold nanorods, the improved St¨obe method to get silica-coated gold nanorods(Au@Si02),and then, the physical properties including shapes、disperbility and of thesilica-coated gold nanorods are characterized by transmission electronmicroscopy(TEM) and UV-vis spectrometer, the silica-coated gold nanorods(Au@Si02) have the same size, good dispersion, and conserved absorption peaks at500nm,825nm.2. The cytotoxicity of the silica-coated gold nanorods were assessedby cell proliferation assay with CCK-8detection in the cells after in-cubation withvarious concentrations(0-60um) of the gold nanorods in different times. The resultsproved that coating the gold nanorods with a shell of pure transparent silica did notintroduce toxicity to cells, so the silica-coated gold nanorods show a goodbiocompatibility, suggesting that it have broad potential applications in biomedicalfields.