磁性合金粒子的合成及應用

Synthesis and application of magnetic alloy nanocrystal

周尚威(Chou Shang-Wei)

指導教授 ： 陳家俊

國立臺灣師範大學/理學院/化學系/博士(2010年)

摘要

本篇論文中，可調控的鐵鉑合金奈米結構生長被系統地研究。鐵鉑的octapod, cuboctahedron, 以及 nanocube都成功地經由cuboctahedral seed生長而成，同時也藉由高解析電子顯微鏡來瞭解其構造。在溶液反應中，成長晶種上的特殊surfactant-facet bindings可藉由調控反應條件而產生同時也造成了晶種上晶面生長速度的差異。因此我們認為這些鐵鉑奈米結構的生長機制主要是由於cuboctahedral seed上 {111} 及 {100} 晶面生長速率的不同所造成的。特別的是，鐵鉑octapod的奈米結構具有最高的coercivity 及 blocking temperature。主要的因素是octapod本身擁有相當高的體積表面積比及較複雜的表面晶面。另一方面，我們藉由控制反應時間而成功合成不同尺寸的鐵鈷奈米粒子。生長機制主要是由於具有低晶格能的FexCo1-x在反應中產生了Ostwald ripening。同時由XRD的結果可以觀察到鐵鈷奈米粒子結構相的轉變和磁無效層的生成。這樣結構上的變化明顯的影響鐵鈷奈米粒子飽和磁化率的數值。
最後，我們製備3, 6 和12 nm的水溶性鐵鉑奈米粒子，同時這些粒子擁有相當高的生物相容性及低溶血性。特別的是，在生物器官分佈分析中，3 nm 水溶性鐵鉑奈米粒子在腦中表現出很高的濃度。另外12 nm的水溶性鐵鉑奈米粒子則是有最高的循環半生期及體外CT/MRI顯影效果。我們進一步驗證修飾Anti-Her2抗體的鐵鉑奈米粒子在MBT2和被剔除Her2/neu 基因的MBT2細胞上可進行標定顯影。而12 nm鐵鉑奈米粒子在CT及MRI的MBT2細胞標定顯影效果優於3 nm鐵鉑奈米粒子。另外也將修飾Anti-Her2抗體的12 nm鐵鉑奈米粒子藉由靜脈注射至癌化動物體內，結果證明以鐵鉑奈米粒子為顯影劑可以增強CT/MRI顯影效果並且辨識出癌症位置。這些成果指出鐵鉑奈米粒子有潛力成為臨床檢驗上新穎且多工的分子顯影劑。

關鍵字

鐵鉑粒子 ； 鐵鈷粒子 ； 磁性 ； 核磁共振 ； 電腦斷層

並列摘要

The controlled growth of alloy FePt nanostructures was investigated systematically. FePt octapod, cuboctahedron, and nanocube were successfully synthesized from a cuboctahedral seed and examined by the high-resolution transmission electron microscopy (HRTEM). In a solution reaction, the specific surfactant-facet bindings on the growth seed were generated and then, the growth rate of crystal facets on seed was differentiated by the djustments of reaction parameters. Therefore, the formations of FePt nanostructures were mainly attributed to the differences in the growth rate between the {111} and {100} planes of cuboctahedral seeds. In particular, the highest coercivity and blocking temperature of octapods are mainly due to its higher surface to volume ratio and more structural facets. On the other hand, the FeCo particles with different sizes were synthesized through controlling the reaction period. The process of Ostwald ripening was discovered in the FexCo1-x system due to the low lattice energy. Based on the XRD patterns, the transformation of structural phase and formation of magnetically dead layers was observed. Also, the saturated magnetization of FexCo1-x nanoparticles was influenced by their structural changes obviously.
Finally, the water-soluble nanoparticles with the sizes of 3, 6 and 12 nm in diameters were prepared and presented excellent biocompatibility and hemocompatibility. The bio-distribution analyses indicated that 3nm-FePt nanoparticles exhibited the highest brain concentration. Moreover, 12 nm-FePt nanoparticles exerted the highest circulation half-life and image contrast effect in the
in vitro CT/MRI test. Anti-Her2 antibody conjugated FePt nanoparticles demonstrated molecular expression dependent CT/MRI dual imaging contrast effect in MBT2 cell line and its Her2/neu gene knock out counterpart. The 12 nm-FePt outperformed 3nm-FePt in both imaging modalities. Selective contrast enhancement of Her2/neu overexpression cancer lesions in both CT and MRI was found in tumor bearing animal after tail vein injection of the nanoparticles. These results indicate the potential of FePt nanoparticles to serve as novel multi-modal molecular imaging contrast agents in clinical settings.

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