建構一新穎的多功能級可調控藥物釋放系統及適體修飾之奈米氧化鐵核金殼粒子於粒徑效應之探討

Abstract

近年來，由於癌症的死亡率一直高居不下，癌症治療載體的研究一直吸引著許多研究學者的注意。其中，超順磁奈米氧化鐵粒子及其衍生材料一直以來都被廣泛研究於各種治療方面的運用。本篇研究中，我們成功利用共沉澱法合成出超順磁奈米氧化鐵粒子，並利用氧化還原法在其表層合成出奈米金殼。此種金包鐵殼核結構可使我們同時利用氧化鐵的磁性特性以及金的表面及光學特性，達成多功能藥物載體的目的。借由奈米金殼的表面特性，我們利用硫基在奈米金表面修飾上特殊的雙股去氧核醣核酸分子(DNA)序列。借此序列的特性，我們可以同時達到藥物攜帶已及專一性辨識兩種效果。另外，借由改變還原劑的濃度，我們成功的合成出不同粒徑大小的金包鐵奈米粒子。奈米金殼的厚度會影響金包鐵奈米粒子的磁性特性、表面積及其他材料特性，進而影響其在癌症治療方面的運用。首先，在熱療法方面，因為金殼所造成的屏蔽效應，外加射頻磁場後所造成的升溫效果會隨著金殼的加厚而下降。另外，因為表面積的差異，不同粒徑大小的金包鐵奈米粒子可以鍵結的DNA序列數並不相同。隨著粒徑增大，表面鍵結的序列數也會增加，進而影響藥物的攜帶量已及後續化學治療方面的效果。同時，因為我們的DNA序列兼具了專一性辨識的效果，序列數的多寡同樣會影響辨識的效果。最後，載體的細胞毒性是未來應用中很重要的考慮因素。借由體外細胞實驗，我們也證明了我們的載體並不會造成明顯的細胞凋亡。同時我們也證明了我們設計的藥物載體系統在外加射頻磁場的狀況下，可以有效的達到殺死癌症細胞的功效。並且借由熱治療及化學治療兩種方法的加成效果，可以有效的降低化學藥物的使用量，進而降低負作用產生的可能。總結來說，我們成功設計出了具備化學治療、熱治療以及具有專一性的藥物載體，並探討出粒徑大小的影響以利未來的運用。

Recently, due to the high mortality caused by cancer, development of carriers for cancer therapy had engaged a lot of attentions for many researchers. Among these investigations, superparamagnetic iron oxide nanoparticles (SPIONs) and their derivatives have been widely investigated in numerous medical applications. In this study, we have successfully synthesized superparamagnetic iron oxide nanoparticles by co-precipitation method, and then gold nanoshell was coated by reduction method. This Fe3O4@Au core-shell structure served as a substrate for further applications in multifunctional drug delivery system with both magnetic properties derived from Fe3O4 and optical properties derived from gold nanoshell surface. Because of the specific surface characteristic of gold nanoshell, we could modify special-designed sequence of DNA with thiol bonding. By means of the sequence including not only an aptamer which had been demonstrated with specific binding ability, but also CG-rich fragments which carried doxorubicin (DOX) as anticancer drug, both the drug loading and specific targeting could be achieved . By triggered with high frequency magnetic field (HFMF), high release percentage could be achieved efficiently in relatively short period of time. Besides, by adjusting the concentration of reduction agent, we had synthesized Fe3O4@Au with different size distribution. The thickness of gold nanoshell would influence of Fe3O4@Au in magnetic, surface area and other physical properties, which also affected the performance for cancer therapy. First, temperature increment caused by high frequency magnetic field would decrease with the increasing thickness of nanoshell due to the shield effects. Next, larger surface area, which leads to higher DNA binding concentration, relatively carry more DOX molecules. This phenomenon further results in the difference of chemotherapeutic ability. At last, cytotoxicity of our dsDNA-conjugated Fe3O4@Au drug carrier was investigated under concern for future applications. No obvious apoptosis by in vitro cell viability test exhibited good biocompatibility of our carriers. At the same time, our drug-capsulated carriers had been proved to eliminate cancer cell under HFMF. With both effects of chemotherapy and hyperthermia, lower minimum amount of drug that has to be used was predicted, which means side effects could be reduced effectively. In conclusion, we have successfully built a release- controlled drug delivery system based on a special-designed drug carrier under HFMF treatment, in which chemotherapy, hyperthermia and specific targeting were all integrated.. Moreover, the study of size effect demonstrated that sizes of these particles act as a controllable and efficient factor for drug delivery behavior and the system tend to be more completed consequently.