單步驟雙乳化法製備奈米複合藥物載體應用於磁場操控釋放及生物顯影

Abstract

在本研究中，發展出以單一乳化步驟即可合成出水-油-水雙乳化結構的中空奈米複合藥物膠囊，且只需要單一兩性高分子-聚乙烯醇(PVA, Polyvinyl alcohol)，與油相奈米氧化鐵粒子作為原料，不必依賴其他乳化劑或界面活性劑的參與。由於聚乙烯醇本身具有界面活性劑的功能，而在水油平衡值的實驗當中，驗證了聚乙烯醇在特定分子量範圍之內，具有同時穩定油/水和水/油介面的能力，故單一高分子即可形成雙乳化結構的中空載體。隨著分子量的增加，聚乙烯醇的疏水度會隨之增加，使分子間極性增加影響載體形成之結構，此研究中也呈現了利用不同分子量的聚乙烯醇合成出中空以及實心的奈米膠囊合成之奈米膠囊大小均在200奈米以下，在進入生物體內時較不會造成副作用。聚乙烯醇及奈米氧化鐵具有高生物相容性，也降低了奈米膠囊的生物毒性。而有關膠囊的特性，由於奈米氧化鐵具有超順磁性，使奈米膠囊可當作磁振造影顯影對比劑，以及能夠用於磁熱療，並可以利用磁導引至特定區域再施加磁場來刺激藥物釋放，達到更佳的療效。由於此奈米中空膠囊特殊的結構，可同時在親水性的核內包覆水溶性藥物、疏水性的外層中包覆油溶性的藥物。我們採用了兩種最常用的抗癌藥物：油溶性的太平洋紫杉醇(Paclitaxel)及水溶性的小紅莓(Doxorubicin)來探討藥物釋放的特性，並選用兩種癌細胞：HeLa, MCF-7進行細胞實驗。首先在藥物釋放機制的分析中，因為藥物分子從外層與內核擴散進入溶劑中的路徑不同，可以發現中空和實心結構的載體具有不同的藥物釋放動力學。而兩種藥物的自然釋藥率都極低，顯示中空奈米膠囊保護藥物的優異能力。當施加磁場時，奈米氧化鐵粒子受擾動而破壞載體，可促使藥物快速釋出。證明了此中空奈米膠囊不僅可同時攜帶兩種不同特性的藥物來提高用於治療時的療效，並可以操控釋放，乃一極具潛力的藥物載體。而在細胞實驗中，經過表面修飾後讓中空奈米膠囊可以對癌細胞有標靶的能力，可以大幅提高癌細胞內的藥物累積及降低對正常組織的毒性。再結合磁場操控藥物釋放以及磁熱療，可以達到更佳的抗癌效果。而雙重藥物的結合，也大大提升了抑制癌細胞的能力，而且在中空奈米膠囊的保護之下，可避免雙重藥物對正常組織的傷害。此多功能奈米複合藥物膠囊，可望作為新一代的藥物治療系統。

In this study, one-step double-emulsion magnetic hollow nanocapsule (HNCs) was successfully designed. Without other emulsifier or surfactant, we used only one amphiphilic polymer, Poly vinyl alcohol (PVA), incorporated with hydrophobic magnetite nanoparticles. PVA can act as a surfactant, and is able to stabilize W/O and O/W interfaces in the meantime when the molecular weight (MW) is in certain range that we have verified in HLB (hydrophilic-lipophilic balance) test. Since hydrophobicity of polymer increases with MW, it also affects the morphology of nanocapsules. We display the hollow/spherical change in this report. Size of HNCs was below 200 nm and is appropriate for entering human body. HNCs is low cytotoxic because PVA and magnetite nanoparticles are biocompatible. HNCs possesses outstanding advantages that it can act as MRI contrast agent and can be used in hyperthermia since the present of superparamagnetic magnetite nanoparticles. Drug release can be controlled by applying AC magnetic field. Hydrophilic and hydrophobic molecules can be encapsulated at the same time because of the water-in-oil-in-water structure of HNCs. We use two common anticancer drugs, Paclitaxel (PTX) and Doxorubicin (DOXO) to discuss the kinetic of drug release. And choose two cancer cells, HeLa cell and MCF-7 cell to demonstrate in vivo experimental. Through drug release profiles we analyzed the releasing mechanisms dominated by different structures. Both drugs behaved low nature release revealed the drugs were well encapsulated in HNCs. Drugs released in a burst-like way when exposed to AC magnetic field. In cell culture, we coupled a targeting ligand to surface of HNCs. Hence HNCs could target cancer cells to enhance the activity of anticancer drugs by high intracellular drug level. Magneto-induced hyperthermia and chemotherapy showed high cancer cell inhibit efficacy. Dual-drug delivery behaved high anticancer activity, and the site effect caused by two drugs might be diminished in the help of HNCs. In summary, HNCs has great potentials in biomedical applications including co-delivery, controlled release, targeted therapy and bioimaging.