開發多功能奈米載體應用於細胞專一標的與抗癌藥物傳遞之研究

Development of multifuctional nano-carrier for specific cell targeting and anti-cancer drug delivery

賴千蕙(Chian-Hui Lai)

指導教授 ： 林俊成

國立清華大學/理學院/化學系/博士(2012年)

摘要

本論文的研究是著重於發展醣體功能化的奈米粒子(nanoparticle, NP)以及細胞專一標的、生物影像和癌症治療等多方面運用之研究。表達在HepG2細胞表面的去唾液酸醣蛋白接受器 (Asialo-glycoprotein receptor，ASGP-R)可以專一性識別非還原末端(non-reducing end)含有半乳糖 (galactose)或乙醯胺基半乳糖 (N-acetyl-galactoseamine，GalNAc)的醣體(glycans)，因此選擇ASGP-R作為標的蛋白質接受器(receptor)進行研究。不同奈米載體如磁性奈米粒子、二氧化矽奈米粒子和孔洞材料奈米粒子表面裝配具有專一標的配位基(ligand)-其為三價體半乳糖。此三價體半乳糖分子同時也裝配到多價體(dendrimer)分子(dendritic glyco-borane, DGB)結構體上去發展中子捕獲抗癌試劑。我們利用以奈米粒子(NP)或是樹狀體(dendrimer)當作良好的多價載體(multivalent carrier)，結合有機合成方式，使奈米粒子表面或是分子裝配三價半乳糖，再經由受質引導的吞噬作用(receptor- mediated endocytosis)專一性的標的HepG2肝癌細胞。在此篇研究中，所有的奈米粒子表面皆有修飾螢光基團(Cyanine 3, Cy3)，螢光基團的修飾是經由不同的化學競爭反應，使奈米粒子表面除了裝配螢光團之外，奈米粒子仍可修飾幾乎相同表面高濃度的配位基-半乳糖。
利用化學共價鍵結的方式在磁性奈米粒子表面同時修飾具有不同比例的螢光團和半乳糖衍生物，用以發展多功能HepG2細胞專一標的之試劑。經由實驗證實，半乳糖衍生物修飾之磁性奈米粒子可以經由受質引導的吞噬作用專一地進入HepG2細胞，並且T-Gal-s-Cy3@MNP被此細胞吞噬的最多，同時我們發現，倘若能夠在奈米粒子表面修飾之小分子配位基可以調整其空間位向使其配合接受體的空間排列，則可使經由受質引導的吞噬作用發揮到最大。在此處的研究，所有醣體修飾的奈米粒子都不具有毒性，在生物應用上應有很大的潛力。
利用有機合成的方式，合成雙烯架橋分子使其裝配在螢光二氧化矽奈米粒子表面，藉此增加表面可修飾官能基的數量與增加極高反應性，二序列兩次點擊反應包含strain-promoted azide-alkyne cycloaddition (SPAAC) 和 Cu(I)-catalyzed azide-alkyne cycloaddition(CuAAC)來建構表面具有抗癌藥物(paclitaxel, PTX)和三價半乳糖體的螢光二氧化矽奈米粒子，此方法中，昂貴的化合物或是不易合成的分子可經由SPAAC的形式裝配到奈米粒子表面，因其反應不須外加任何試劑，更可在反應之後直接回收珍貴之分子，而利用三價半乳糖分子修飾的表面除了可以增加水溶性之外亦可以有專一標的HepG2細胞的功能，此種TGal-PTX@Cy3 SiO2NP奈米碳針表面裝配包含螢光、專一標配位基和抗癌藥物，可以提供第一時間(real-time)細胞專一標的之抗癌藥物細胞毒殺效果。
在硼中子捕獲治療中(BNCT)，必須仰賴傳遞除足夠的10B原子至標的之癌細胞，施予中子至含10B細胞，激發態之不穩定的硼分子隨後放出一定距離的能量，最終死細胞，然而在此領域的研究中，常受限於含硼藥物的毒性、低水溶性與低癌細胞專一性，因此在筆者研究中發展兩種中子捕獲試劑，包含醣體多價體
(dendritic glyco-borane, DGB)和孔洞材料架構之T-Gal-B-Cy3@MSN，DGB多價分子與T-Gal-B-Cy3@MSN皆具有三價半乳糖，可能供水溶性與專一標的性，在DGB的實驗中證實，其為極好的硼中子捕獲試劑，跟美國食品藥物管理局准許的硼中子試劑BSH比較，具有十倍以上的毒殺效果，在孔洞材料架構之T-Gal-B-Cy3@MSN方面，是發展「特洛伊木馬」的策略，孔洞材料具有多孔體積，可置入極大值的含硼藥物 (此處用o-carborane)，平均一個奈米粒子就要含約重量百分之五十的硼原子在其內部，這樣的策略解決孔洞材料當藥物載體之藥物釋放動力學之限制，在表面又修飾三價半乳糖分子，可以提供專一標的HepG2細胞之能力，相信這兩種硼中子捕獲試劑，應在中子捕獲治療上有極大的潛力。

關鍵字

奈米粒子 ； 專一標的 ； 抗癌藥物 ； 表面修飾 ； 硼中子療法 ； 二次序列點擊反應 ； 生物影像

並列摘要

The work presented in this thesis focuses on the development of carbohydrate-functionalized nanoparticles (NPs) and their diverse biomedical applications such as cell-specific targeting, imaging and cancer therapy. The asialoglycoprotein receptors (ASGP-Rs), which can specifically interact with galactose (Gal) or N-acetyl-galactosamine (GalNAc), were chosen as a way to target HepG2 cells. Targeting ligands were presented on NP carriers such as magnetic nanoparticles (MNPs), silica oxide nanoparticles (SiO2NPs) and mesoporous silica nanoparticles (MSNs). Moreover, a dendrimer-like multivalent galactosyl carborane (dendritic glyco-borane, DGB) was developed for potential application in boron neutron capture therapy (BNCT). Multivalent carriers such as NPs or dendrimer-like molecules decorated with trivalent-Gal moieties are good systems for HepG2 cell-specific targeting via receptor-mediated endocytosis. The fluorescent NPs (MNP, SiO2NPs and MSN) were fabricated by a competition method to incorporate Cy3 without the loss of the original surface amine density that allows for the loading of high concentrations of targeting ligand.
The fluorescent dye Cy3 and galactose derivatives were covalently assembled with different ratios on the surfaces of MNPs to produce multifunctional HepG2 cancer cell–targeting agents. We found that the specific uptake of galactosyl-conjugated MNP by HepG2 cell via receptor-mediated endocytosis and T-Gal-s-Cy3@MNP was the most efficiently ingested MNP tested. Moreover, we found that by adjusting the spatial arrangement of the ligands on MNPs to match the distance between carbohydrate binding sites on the receptor, the increase in cellular uptake by multivalent presentation of the ligand could be maximized. All the glyco Cy3@MNPs are not cytotoxic, indicating that they may potentially be used for in vivo applications.
We also used sequential double click chemistry (SDCC) involving strain-promoted azide-alkyne cycloaddition (SPAAC) and Cu(I)-catalyzed azide-alkyne cycloaddition to assemble an anticancer drug (paclitaxel, PTX) and a targeting ligand (trivalent galactosside, TGal) on a fluorescent silicon oxide nanoparticle (SiO2NP) by using a di-alkyne linker as a bridge which can increase the surface availability for further functionalization. The expensive compound used in SPAAC can be easily recovered due to the absence of other reagents in the reaction mixture. The use of a trivalent galactosyl ligand, which interacts with the ASGP-Rs on the surface of HepG2 cells, not only provides a targeting function, but also overcomes the inherent low water solubility of PTX. The presence of a fluorescent probe, a targeting ligand, and an anticancer drug on the multifunctional TGal-PTX@Cy3SiO2NP allows for real-time imaging, specific cancer-cell targeting and cell-killing effects that are similar to PTX.
Boron neutron capture therapy (BNCT) relies on the uptake of a sufficient number of 10B atoms by the target cell. The cell is then being irradiated with neutrons and the absorption of neutrons by 10B atoms leads to the release of energy and finally to the death of the cell. The success of BNCT requires a sufficient number of 10B atoms to be delivered to the targeted cells and the main challenges often arise from the low water solubility of boron compounds, the unselective uptake of the cancer cell, and the toxicity of boron. Two types (dendritic glyco-borane, DGB and T-Gal-B-Cy3@MSN) of boron neutron capture therapy (BNCT) agents were design as third generation BNCT agents. DGB which possesses trivalent Gal moieties and trivalent carboranes was synthesized and tested as a potential cell-targeting agent in BNCT with HepG2 cells. DGB improved the delivery of boron to HepG2 cells, and neutron irradiation data show that DGB exhibits a ten-fold improvement at killing HepG2 cells compared to BSH, an FDA-approved drug. Another strategy we pursued was to use mesoporous silicon NPs (MSNs) as 10B carriers for a “Trojan horse” type approach. T-Gal-B-Cy3@MSN as BNCT agent has large pore volumes which allow for the loading of o-carborane (almost 50% boron atoms per MSNs particle). This resolves previous limitations concerning the drug release kinetics of MSNs. Moreover, the trivalent Gal moiety serves as a targeting ligand for the targeting of HepG2 cells. We believe that our approach provides new insights on the development of dendrimer- and MSN-type BNTC agents.

並列關鍵字

Nanoparticle ； Specific Targeting ； Anticancer drug ； Surface modifiaction ； BNCT ； Sequence double click chemistry ； Cell image

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