設計與製備具顯影與磁場刺激藥物釋放之多功能型奈米藥物輸送載體元件

Abstract

在控制藥物釋放的系統中，尤其在是在及外力場刺激下作用之智慧型藥物釋放系統，在全球已經引起各學界與業界人士的注意。在本論文中，利用材料與藥物的結合，設計與製備一種具多功能性的磁性藥物奈米載體，除了具有利用外部磁場控制釋放藥物之功能，並可以同步監測藥物釋放的情形。然而，傳統的藥物釋放，僅利用藥物載體的特性與所在的環境變化來運作，在人體中並未真正達到完善地控制釋放的目標。故本論文根據此創新的研究構想，使用"磁場"的非接觸力特性，達到遙控藥物載體快速藥物釋放的效果。首先，用奈米級氧化鐵與明膠/幾丁聚醣製備複合材料水膠，該水膠可以利用外加高頻磁場驅動水膠內部氧化鐵生熱與轉動，進而使該溫度敏感型水膠高分子結構鬆散，達到快速藥物釋放的效果。為達到可應用於體內之藥物載體，因此將藥物載體奈米化，提出利用新穎製程控制，先將poly-(N-vinyl-2-pyrrolidone) (PVP)做為奈米核之結構，其表面具有螯合鐵離子的特性，再利用共沈法，將單晶奈米氧化鐵殼層成長於表面上，發展具有磁敏感性的奈米核殼膠囊結構，將藥物完美的包覆於該奈米膠囊當中，在未加磁場的狀態下，該奈米膠囊藥物自然釋放量趨近於零，如此可大幅降低高毒性藥物在體內的副作用，然而當此奈米膠囊抵達治療位置時，可以利用外部的磁場刺激磁奈米載體，控制藥物快速的局部釋放，有效的控制藥物釋放於定點。此外，利用奈米晶體成長技術，架接具光學特性的量子點於奈米膠囊的表面上，此具光學特性量子點，可以利用其螢光顯影，來追蹤該奈米膠囊於體內的位置，並且搭配磁場的控制下，可監測藥物於定點釋放的情形，可用來評估釋放量對於疾病的影響。並且奈米膠囊的表面經由化學表面改質，可帶有標靶癌細胞的分子，在體內中大量提升奈米膠囊進入癌細胞的效率。此奈米複合膠囊搭配外加磁場的控制的結構元件，期望在未來可達到快速有效率的局部釋藥於腫瘤細胞，並同時於體內偵測藥物釋放情形。 同時，為了達到包覆油相藥物與提升包藥率，設計另一種多功能性的磁性奈米膠囊藥物載體，尺度約為100奈米，將油相藥物與氧化鐵作為奈米核，並在載體外部包覆奈米二氧化矽殼層，達到大幅降低藥物自然釋放的效果；並藉由螢光染劑標定二氧化矽殼層，可使該載體可同時具有控制釋放藥物與顯影之功能。未加磁場的狀態下，由於二氧化矽為堅固緊密之結構，此奈米膠囊藥物利用奈米殼層，將藥物包覆於載體當中，可大幅降低載體漏藥性與高毒性抗癌藥物在體內的副作用，然而當此奈米膠囊抵達需要特定位置時，再施加外部的磁場刺激磁奈米載體，控制藥物快速的局部釋放，將大量的藥物釋放於治療之位置，達到治療的效果。此外，磁性奈米粒子還能利用MRI來作為細胞追蹤的標的，在磁性奈米粒子表面接枝特定抗體，使此特殊架接的奈米粒子可以與特定細胞之抗原結合，以達到標定式之藥物釋放。本研究後期將利用靜脈注射的方式，將奈米膠囊藥物載體注射入老鼠的血管內，來作一些體內之標定式藥物釋放之測試，並觀察體內腫瘤細胞的治療效果，期望達到新一代的治療效果。

Controlled drug release has been received greatest attention worldwide, especially stimuli-responsive drug-delivery systems. In order to accelerate the response of an adaptive nanocarrier to stimuli, the use of the magnetic-sensitive nanomedical platfoems as a new type of actuator has been developed in this thesis. In first part, ferrogels composed of thermosensitive polymers, gelatin and chitosan, and iron oxide nanoparticles were triggered by a high frequency magnetic field to achieve pulsatile drug release. Under cyclic exposures to the high frequency magnetic stimuli, a highly controllable and repeatable burst release were exhibited with desirable precision from the ferrogels. In second part, the drug carriers were designed and narrowed down to nanosize. A novel core-shell nanosphere which was constructed by a poly-(N-vinyl-2-pyrrolidone) (PVP)-modified silica core with an outer layer of single-crystal iron oxide shell was fabricated. This drug delivery nano-device capable of providing controlled release of precise dose of therapeutic molecules when body needs and in particular, zero release when no need in the host, is critically important for clinical practices. The nanosphere showed outstanding release-and-zero-release characteristic via the addition and removal of an external manipulation of high-frequency magnetic field, respectively. Upon magnetic stimulus, the single crystal iron oxide shell with a thickness in a few nanometers demonstrated atomic re-arrangement, forming lattice of varying orientations, where inter-crystal boundary were developed, allowing drug eluted or no released in a reversible behavior. Further stimulation causes rupturing, i.e., permanent damage, of the shell, where drug eluted rapidly and can hardly be ceased, even after removal of the stimulus. Such novel core-shell nanospheres showed a fast cancerous cell (human cervical cancer cell line) uptake behavior, which implies a highly efficient potential to achieve anti-cancer therapy when anti-cancer drug is delivered. On the other hand, constructing with other functional nanoparticles like quantum dots can form the multifunctional magnetic nanocarriers that could be applicable to a variety of fields as a new driving mechanism. Combining with fluorescent quantum dots, the nanocarriers can be tracked in the human body. The optical properties also can be tunable while applying the magnetic field for sensing the drug release. Drug release rate at on-off operation of AC magnetic fields (hyperthermia effects) and the conditions of killing-tumor cells also would be investigated. Finally, the magnetic nanocapsules capable of carrying hydrophobic drug molecules were synthesized as the bifunctional magnetic vectors that can be triggered for control release of therapeutic agent by an external magnetic field. The drug release profiles of cpsules can be well-regulated through an ultra thin layer of silica shell. Remote control of drug release from the nanocapsules was successfully achieved using an external magnetic field where the core phase being structurally disintegrated to a certain extent while subjecting to magnetic stimulus, resulting in a burst release of the encapsulated drug. However, a relatively slow and linear release restored immediately right after removal of the stimulus. More than surprisingly, the nanocapsules demonstrated a relatively high uptake efficiency by HeLa cell line. In addition, the magnetic nanoparticles still provides some advantages, such as magnetic resonance image (MRI) for cell labeling and grafted probe-proteins (such as biotin or antibody) onto magnetic nanoparticles for “target” drug delivery. Therefore, the multifunctional drug-carriers is able to be triggered by thermal and magnetic changes, and especially put emphasis on “target” drug-delivery using MRI, cell labeling or others detecting technique.