設計與製備多功能孔洞二氧化矽基板奈米平台應用於提高療效與增強影像之研究

Abstract

奈米載體結合診斷與治療等多功能的系統，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、奈米粒子與藥物的結合，設計與製備具多功能的磁性奈米載體與具高強度光反應的顯影載體。除了具有利用外部磁場或雷射光控制釋放治療之功能外，並可以同步監測奈米載體的位置。然而，目前的多功能奈米載體仍然具有許多缺點需要改善，例如:無法長時間監控載體，容易受外界環境影響載體的穩定性。為了改善這些缺點，本論文發展出一個結合診斷與治療於一身的多功能二氧化矽載體。於本論文第一部分研究，首先，以孔洞二氧化矽當作基材，將抗癌藥物載入孔洞中，並利用單分散氧化鐵奈米粒子藉由化學鍵和孔洞二氧化矽奈米粒子鍵結。此化學鍵提供氧化鐵奈米粒子和孔洞性二氧化矽奈米粒子有緊密的鍵結，並且當作奈米蓋子完整覆蓋於二氧化矽的孔洞表面。在沒有外加磁場刺激之下，近乎沒有藥物從磁性奈米載體裡面外漏出來。然而，當我們施加可控制的外加磁場刺激之下，磁性奈米載體表面的氧化鐵粒子將會脫落，使得二氧化矽孔洞外漏出來，進而讓孔洞裡面的抗癌藥物釋放出來。此磁性奈米載體具有高強度的核磁共振顯影效果與螢光顯影的特性，比較於其他類似的結構更為出色。 另一方面，由於孔洞二氧化矽材料受限於孔洞的大小，孔洞太小無法攜帶大分子藥物與功能性奈米粒子，限制其應用性。因此，於論文第二部分，我們將功能性量子點載入於10奈米孔洞大小的二氧化矽球中，並且透過非共價鍵的生物分子架接標靶分子，此載體具有良好的光對比特性與多重色碼標示的優點，更可以大幅降低量子點會受到外界環境影響的特性，保護量子點維持其量子效應，並且改善量子點的生物相容性差的缺點，最後在標靶分子方面，具有標靶分子的載體在腫瘤細胞的標靶具有很明顯的差異。透過此簡易的乘載方法，使量子點在生物醫學應用上有很大的突破。 同時，在第三部分，設計另一種新型多功能奈米複合結構的奈米載體，其結構是由奈米金棒填滿孔洞二氧化矽球，並且具有高度強度且穩定性的光聲顯影效果。可當作一種新型的光聲顯影之顯影劑，這種光聲顯影是一種結合超音波及雷射所發展出之一種具有低成本及良好顯影的技術，可以應用偵測腫瘤及一些的病態組織，而其中當然最重要的是顯影劑。而奈米金棒成長填滿於孔洞奈米結構，則可以應用在這方面來當顯影劑，此奈米金棒於高強度的奈米秒發間歇性雷射照射之下，仍然具有且保留良好的光學特性與光熱穩定度，而且無論於生物體外和生物體內都具備了穩定的光聲顯影和高效率的熱治療，由此可以得知奈米金棒成長填滿多孔性球具有強而有力的奈米診斷治療能力。此外，奈米金棒填滿多孔性球也具有良好的生物相容性與低毒性的特性。所以，奈米金棒填滿孔洞球，的確可以成為一個具有熱治療與光聲顯影的奈米診斷治療平台。最後，將此奈米金棒填滿孔洞球與磁性氧化鐵結合，形成同時具備有磁特性、光特性奈米載體與核磁共振顯影和光聲顯影雙重顯影的功能。利用磁導引的特性，在光聲顯影方面，提升了將近7.2倍的影像強度，另一方面，應用於幹細胞治療上，奈米載體經由幹細胞吞噬之後，透過磁導引的方式，將幹細胞引導至中風部位，大幅降低於人體中幹細胞90%會被肝跟肺所代謝。未來期望能透過多功能的奈米載體達到新一代的治療與診斷效果。

Multifunctional nanoprobes have been received greatest attention worldwide, especially combining diagnostic and therapeutic functions. In order to enhance imaging and therapy efficiency, the use of the mesoporous silica nanoparticles as a new type of actuator platforms to anchor guest molecules has been developed in this thesis. In first part, an anticancer drug, (S)-(+)-Camptothecin (CPT)) were encapsulated into the mesoporous silica nanoparticles which is chemically capping by Fe3O4 to prevent drug elapsing and remote-controllable. With an external high frequency magnetic field (HFMF) trigger, the Fe3O4 nanocaps can be removed from surfaces of mesoporous silica vehicles due to the breaking of chemical bonds and then subsequently lead a fast-responsive drug release and concentration gradient for second drug release. The nanosystems also show the potential of magnetic resonance imaging and fluorescence imaging for diagnostic. In second part, the meosporous silica matrix was enlarged the pore size to incorporate quantum dots for bioimaging. A highly hydrophobic mesoporous silica nanoparticle with pore size greater than 10 nm was incorporating quantum dots and bridging the targeting peptide cRGD by using noncovalent biotin-streptavidin link. Their outstanding optical contrasts render these highly fluorescent QDs ideal fluorophores for wavelength-and-intensity multiplex color coding. This nanoprobe is able to provide highly chemically stability for the quantum dots and maintain the high quantum yield even in the low pH value environment. For the targeting effect, the cRGD-encoded lipid coated QDs tagged nanobeads exhibited significantly increased αvβ3-expressing cell targeting toward MCF-7 breast cancer cells over the αvβ3-low expressing in HeLa cervix cancer cells. Furthermore, in MCF-7 xenograft nude mice, the cRGD-encoded nanoprobes revealed prolonged accumulation time at tumor site. In third part, we a new type of theranostic system based on gold nanorod-containing mesoporous silica nanobeads with exceptionally efficient and stable photoacoustic imaging modality was synthesized. The novel nano-seaurchin structure is characteristic of high-density and well-dispersive gold nanorods (AuRNBs) in one mesoporous silica nanobead. The optical properties and photothermal stability of porous silica nanobeads with pore-filled gold nanorods (AuRNBs) under intense irradiation with nanosecond laser pulses were investigated by UV-Vis spectroscopy and transmission electron microsocopy. The AuRNBs showed increased photothermal stability and retained their superior optical properties under much higher fluence laser pulses at 10 mJ/cm2. The AuRNBs also provided a stable photoacoustic signal and highly efficient hyperthermia effect both in vitro and in vivo, indicating a powerful theranostic modality. Finally, the mesoporous silica nanobeads tagged iron oxides nanoparticles, where the nanoporosity was further filled with gold nanorods. The magnetic nanoprobes could be controlled by external magnetic navigation, capable of performing MR and photoacoustic imaging modalities simultaneously. The magnetic nanoprobes showed that the r1 value was 1.205 s-1mM-1Fe, and the r2 value was 127.89 s-1mM-1Fe. The higher transverse (r2) relaxivities could be attributed to the silica nanobeads tagged the Fe3O4 NPs in the pore forming a well-dispersive and chemical stable condition. On the other hand, the PA contrast could be further increased 7.2 times PA signals by an external magnet PA signals compare with without an external magnet applied, demonstrating their ability to perform active magnetic guide. The magnetic nanoprobes could be internalized efficiently toward the stem cells and a prolonged retention for 48 hours. In addition, the magnetic nanoprobes were successfully achieved using an external magnet guiding the stem cells to the stroke areas and cell labeling by MR images for in vivo MCAO stroke mouse. Therefore, this multifunctional nanoprobe not only provides exceptionally highly photothermal stability but also remote-controlled property, which offers potential advantages for carrying/homing stem cell, therapy and dual imaging.