聚氰基丙烯酸酯奈米載藥粒子的研究

Study on Drug-Loaded Poly(alkyl 2-cyanoacrylate) Nanoparticles

黃基毓(Chi-Yu Huang)

指導教授 ： 李育德

國立清華大學/工學院/化學工程學系/博士(2006年)

https://doi.org/10.6843/NTHU.2006.00704

摘要

聚氰基丙烯酸烷基酯（PACA）是具生物可分解和生物相容性的材料，利用乳化聚合反應可製備載負多種不同種類藥物的PACA奈米粒子。由於此材料的降解速率甚快，因此，特別適合做為抗腫瘤藥物的載體粒子。於PACA奈米粒子的研究中，一直只使用單一種單體聚合而成的均相PACA粒子，其快速且無法控制的降解速率，限制此材料應用於長效型和需具有特定藥物釋放速率的載體材料。相較於其它常用的藥物載體材料，PACA過於快速的降解速率易使得產生的降解產物濃度過高，造成此材料的毒性偏高。因此，在本研究的第一部份主要是製備和鑑定可控制降解速率和親疏水性的核-殼（Core-shell）奈米粒子。此奈米粒子主要是使用氰基丙烯酸正丁酯(n-Butyl cyanoacrylate; BCA）和氰基丙烯酸異辛酯（2-Octyl cyanoacrylate; OCA）兩種單體，在0.01 N的鹽酸水溶液中，以Pluronic F127為乳化劑，進行陰離子乳化共聚合反應所製得。各種不同BCA/OCA進料組成所製得的粒子，均為粒徑小於100 nm、粒徑均一度高且形狀為完整圓球形的粒子。生成粒子的粒徑大小、表面電位（Zeta potential）高低、高分子的分子量與親疏水性和降解速率，均受BCA及OCA組成的影響。體外粒子水解研究中，顯示改變共聚物中BCA和OCA的組成比例，可控制粒子的水解速率，最高與最低水解速率間的差異可達200倍。分析粒子與生成的共聚高分子，推論由BCA/OCA所組成的粒子形態，粒子的內層可能是由富含OCA的共聚高分子鏈端所組成；而富含BCA的共聚高分子鏈端，為位於粒子的外殼層的核-殼粒子結構。體外細胞毒性的結果顯示，POCA的奈米粒子的毒性相較於PBCA的奈米粒子，其毒性甚低；然而，BCA/OCA所組成的奈米粒子毒性卻與PBCA粒子的毒性相近。
一般製備載藥PACA粒子的方式，是將藥物先溶於反應分散液中，於氰基丙烯酸烷基酯單體進行乳化聚合反應過程中，將藥物包覆於粒子內；或是於PACA粒子生成後，再將藥物溶入膠體乳液內，生成的粒子利用吸附的方式載負藥物。所以可被粒子載負的最大藥物重量，即為藥物可溶解在分散液中的重量。使用此傳統乳化聚合法製備載負如紫杉醇的高疏水性藥物之PACA奈米粒子，可預期所得載藥PACA粒子的載藥率甚低。
為解決PACA無法製備載負高疏水性藥物粒子的缺點，本論文第二部份利用迷你乳化聚合反應，使用Pluronic F127為界面活性劑，以求製備兼具高載藥率和高包覆率的載負紫杉醇之PBCA奈米粒子。實驗結果顯示，利用迷你乳化聚合反應所得載負紫杉醇之PBCA粒子，不論在載藥率或包覆率，均為乳化聚合反應所製得載藥粒子的三倍（進料BCA中含有紫杉醇濃度為1 % (w/w)）。使用具不同紫杉醇濃度的BCA單體溶液，經由迷你乳化聚合反應所製得的載藥粒子，載藥率和包覆率均隨紫杉醇在BCA單體中的含量增加而增加，最高可得載藥率4 % (w/w) 的載藥粒子，同時對藥物的包覆率亦達80 % (w/w)。雷射測徑儀測得利用迷你乳化聚合反應製備的載藥PBCA粒子，粒子的平均粒徑約為100 nm，且由場發射掃描式電子顯微鏡觀察載藥PBCA粒子，顯現所得粒子為獨立完整的球狀粒子。X射線繞射儀（XRD）所測得載負紫杉醇之PBCA粒子的圖譜，顯示不論是利用乳化聚合反應或迷你乳化聚合反應所製備的載藥粒子，均未有紫杉醇的結晶峰產生。因此，可推論所製備載負紫杉醇的PBCA粒子，紫杉醇可能是以分子、無結晶或是小於XRD偵測極限的小結晶形態分佈於載藥粒子中。載負紫杉醇之PBCA粒子於pH=7.4的磷酸鹽緩衝溶液（PBS）中的藥物釋放動力曲線顯示，乳化聚合反應製備的載藥粒子呈現明顯雙階段的釋放曲線，初始時粒子表層的藥物被快速的釋出，隨後，粒子內的藥物才被緩慢的釋出。然而，相較於乳化聚合反應，迷你乳化聚合反應所製備的載藥粒子，藥物突釋效應的程度較低，顯示利用迷你乳化聚合反應所製備的載藥粒子，有較大比例的藥物分佈於載藥粒子的內部。利用乳化及迷你乳化所製備的載藥PBCA粒子，於PBS中進行藥物釋放96小時後，均有80 % (w/w)以上的藥物可自粒子中被釋放出來。再者，藥物釋放速率隨載藥粒子載藥率增加而降低。

關鍵字

氰基丙烯酸酯 ； 奈米粒子 ； 藥物釋放 ； 紫杉醇 ； 迷你乳化

並列摘要

Polyalkylcyanoacrylate (PACA) is a biodegradable and biocompatible material and PACA nanoparticles prepared via emulsion are capable of encapsulating various kinds of drugs and are eminently suitable as anti-tumor drug delivery carrier for treatment of cancer since it’s characteristic of rapid degradation rate. The type used in application and study is homopolymer, fast and uncontrollable degradation rate limit PACA as drug carrier applied for long-term release and met the required drug release rate on various clinical treatments. Compared with other commonly used materials, excessively fast degradation rate of PACA causes the higher cytotoxicity arising from the high concentration of degradation products. Hence, the first part of this research, core-shell type of nanoparticles with manipulated degradation rate and balanced hydrophilic/hydrophobic properties were designed and characterized. The nanoparticles based on the copolymers of n-butyl cyanoacrylate (BCA) and 2-octyl cyanoacrylate (OCA) were prepared by anion emulsion polymerization in 0.01 N HCl solution with pluronic F127 as the stabilizer. These nanoparticles were spherical in shape and with size smaller than 100 nm in a narrow distribution. The particle size, zeta potential, molecular weight, hydrophobicity and degradation rate of the copolymer depended on its composition significantly. In vitro chemical hydrolytic studies indicated that the degradation rate of the NPs could be controlled over 200-fold by adjusting the BCA/OCA ratio. Differential scanning calorimetry measurements verified the existence of copolymer with tapered structure which was induced by the reactivity difference of the monomers. A BCA/OCA core-shell structure is postulated that the OCA rich segments were mainly located in the core of the NPs. The cytotoxicity of poly(2-octyl cyanoactylate) (POCA) is quite lower than that of poly(n-butyl cyanoacrylate) (PBCA) and the toxicity of poly(BCA-co-OCA) nanoparticles is similar to that of PBCA nanoparticles.
The most common approach of preparing drug-loaded PACA nanoparticles is either incorporation during the process of emulsion polymerization or adsorption by the surface of formed nanoparticles. The maximum weight of encapsulated drug is limited to the drug solubility in medium. It is expected that drug-loaded PACA nanoparticles with low drug loading efficiency for hydrophobic drugs such as the most representative drug of paclitaxel.
The second part of this study, the strategy of miniemulsion polymerization is successful to obtain stable paclitaxel-loaded PBCA nanoparticles containing high loading and encapsulation efficiency simultaneously were achieved in the presence of pluronic F127. It was found that both drug loading and encapsulation efficiencies of PBCA nanoparticles prepared by miniemulsion were higher (approximately 3 times) than those obtained by emulsion with similar paclitaxel content in the feed monomer (1 % (w/w)). Furthermore, the loading and encapsulation efficiencies increased concurrently (to a maximum of 4 % and 80 % respectively) with increasing paclitaxel content and these nanoparticles were spherical in shape and with size near 100 nm. XRD patterns revealed that paclitaxel in particles was distributed in the molecular or amorphous state or in the form of small crystals. The in vitro drug release profile of drug-loaded PBCA nanoparticles prepared from miniemulsion exhibited a gradual release; more than 80 % (w/w) of the paclitaxl was released after 96 hours. Thus, miniemulsion polymerization could be used as a successful strategy to effectively encapsulate highly hydrophobic drugs in the PACA nanoparticles.

並列關鍵字

cyanoacrylate ； nanoparticle ； control release ； taxol ； miniemulsion