我們成功利用熱裂解法製備出各種尺寸(5-22 nm)的截面八面體Fe3-δO4奈米粒子，藉由XRD光粉末繞射光譜圖的分析，各個繞射峰面隨著奈米粒子的尺寸縮小而往低角度位移，這個偏移現象與Fe3-δO4顆粒中的陽離子缺陷數(δ)有關，且缺陷數隨著氧化鐵尺寸縮小變多。在XRD、電子繞射、傅立葉轉換影像、縱向XPS組成分析與拉曼光譜鑑定光譜圖中，可看出22 nm尺寸的Fe3-δO4粒子結構中包含了金屬鐵的組成。SQUID的分析顯示，飽和磁化量隨著氧化鐵尺寸而線性增加，其中，22nm尺寸的Fe3-δO4奈米粒子達到最大飽和磁化率值(94 emu/g)，高於塊材的四氧化三鐵的數值( 92 emu/g)。
選擇高磁性22 nm Fe3-δO4來進行不同的表面修飾，分別使用界面活性劑(CTAB)和高分子( PSMA)來達到表面親水改質目地。由於修飾上PSMA的四氧化三鐵具有高於200 mM-1s-1 的r2弛緩速率且比市售的顯影試劑(Resovist)還來的高(91mM-1s-1)，能發展成為高對比能力的的T2顯影劑。體外與體內生物活性顯示，親水性的四氧化三鐵奈米粒子有良好的生物相容性。修飾上PSMA的22 nm Fe3-δO4注射到小鼠體內觀察，藉由量測T2＊鬆弛數值與影像對比分析，結果顯示我們的氧化鐵奈米粒子較市售的Resovist可有效的觀察肝臟影像變化所需時間。
修飾上PSMA的22 nm Fe3-δO4奈米粒子還可以做為藥物載體，例如藉由氫鍵結合策略，攜帶5-FU抗癌藥。結合上述實驗結果，我們製作出的22 nm Fe3O4@PSMA磁性奈米粒子同時結合了MRI顯影和藥物載體功能，未來將朝向“磁感”應答性質的生醫奈米技術平臺發展。

We report the size-controlled synthesis of truncated octahedral Fe3-O4 nanoparticles with sizes varying from 5 to 22 nm. Size-dependent XRD spectra showed that the iron oxide gradually shifted from magnetite toward maghemite as size decrease. The nonstoichiometric Fe3-O4 was expressed the resulting iron oxide nanoparticles, where the cation vacancy numbers were deduced leading to  increase as particle size decrease. Size dependence of XRD, magnetization and Raman measurements indicated that the 22 nm-sized particles displayed the formation of magnetite nanoparticles. The saturation magnetization increased linearly as the particle size increased, with values up to 94 emu/g, which is comparable to bulk magnetite (92 emu/g). XRD, electron diffraction including fast Fourier transform filtering analysis, and depth profiling XPS were conducted, indicating the presence of metallic iron in the 22 nm-sized magnetite resulting in high magnetization.
The high magnetization 22 nm-sized magnetite was engineered by different surface modification strategies using surfactant (CTAB) and polymer (PSMA) resulting in hydrophilic property. The chosen PSMA-coated magnetite have r2 relaxivity large than 200 mM-1s-1, where a commercial Resovist hepatic agent displays 91 mM-1s-1. Aiming to develop highly effective hepatic contrast agents, we injected the PSMA-coated magnetite into BALB/C mice to evaluate the T2* relaxation and image contrast. The results showed a greater signal reduction in liver as compared to Resovist agent.
Simultaneously, the PSMA-coated magnetite with fluorouracil (5-FU) can act as a candidate for drug delivery carriers. Combining theses biomedical effects into a Fe3O4@PSMA fluid system would be further developed into an ultra-sensitive of magnetic response and sensing for bionanomedical platform and applications.

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