Functional Controlled Release Systems Triggered by Photothermal Effect of Gold Nanorods
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1241-XX06-05
Functional Controlled Release Systems Triggered by Photothermal Effect of Gold Nanorods Shuji Yamashita1, Hiromitsu Fukushima1, Yasuro Niidome1, Takeshi Mori1,2, Yoshiki Katayama1,2, Takuro Niidome1,2,3 1 Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan, 2 Center for Future Chemistry, Kyushu University, Fukuoka 819-0395, Japan, 3 PRESTO, Japan Science and Technology Agency, Kawagushi 332-0012, Japan ABSTRACT Gold nanorods, rod-shaped gold nanoparticles, have transverse and longitudinal surface plasmon (SP) bands at visible and near-infrared (IR) regions, respectively. Since the absorbed light energy is converted into heat, photothermal effect of gold nanorods can be triggered without damaging the tissues in the path of near-IR laser light. In this study, we tried to construct controlled release system of functional molecules from surface of gold nanorods mediated by the photothermal effect. First, we evaluated controlled release of poly(ethyleneglycol) (PEG) chains from PEG-modified gold nanorods (PEG-NR). Next, we employed double stranded oligonucleotide as a thermo-responsive dissociating group (DNA-NR). Finally, we evaluated photothermal release of PEG chains mediated retro-Diels-Alder reaction (PEG-DA-NR). For construction of controlled release system of functional molecules, these studies will provide important information about the photothermal reactions of surface molecules on the gold nanorods triggered by near-IR light irradiation. INTRODUCTION Recently, nanoparticles used as a biomaterial have attracted great interest. In these nanoparticles, gold nanoparticles have been studying for long time because of a specific characteristic of optics [1,2,3,4]. Gold nanorods, rod-shaped gold nanoparticles, have strong absorbance at near-IR region corresponding to longitudinal surface plasmon (SP) oscillation. Then, absorbed light energy is converted to heat [6]. Since the near-IR light can penetrate tissues [7], photothermal effect of gold nanorods can be triggered the body without damaging the tissues in the path of near-IR laser light. Gold nanorods are anticipated as functional materials that are controlled by external stimulation. EXPERIMENTAL DETAILS Materials Gold nanorods were provided by a joint research project between Mitsubishi Materials Corp. and Dai Nippon Toryo Co. Ltd. The mean size of the gold nanorods was 65±5 nm and 11±1 nm in longitudinal and transverse directions, respectively. Controlled release of poly(ethyleneglycol) (PEG) chains from PEG-modified gold nanorods An as-prepared gold nanorod solution containing an excess amount of hexadecyltrimethylammonium bromide (CTAB) as a stabilizing agent (1 mL, CTAB: 480 mM, Au: 0.03 wt%) was centrifuged. The supernatant was discarded and the precipitates then
dispersed in water. A thiol-terminated PEG solution (m-PEG5,000-SH, 5 mM, Mw = 5,000, NOF Corp.) was added to the centrifuged gold nanorod solution. The mixed gold nanorod solution was then stirred for 24 h then dialyzed to remove any excess CTAB (molecular weight cut
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