合成具香豆素脂之兩親性PAMAM樹枝狀分子及其對DNA結合與光致釋放能力之探討

Synthesis of amphiphilic PAMAM dendrons with photocaged coumarin ester towards DNA binding and photo-triggered release

歐家褕(Jia-Yu Ou)

指導教授 ： 朱智謙

中山醫學大學/健康管理學院/應用化學系碩士班/碩士(2016年)

摘要

遠程調控藥物傳遞系統使用觸發媒介主動控制人體中的藥物載體釋放藥物，因此藥物的釋放率大大增加同時提升了治療效果。在所有觸發媒介中，光為一安全，且具高穩定性與調控性之能源，可依所需選擇光的波長，照光的時間、區域，因此我們欲合成出具有良好釋放效率之光敏感載體。香豆素為一被廣泛應用於光致釋放系統之物質，因此我們經由五步有機反應，合成出以香豆素為光敏感基團的兩親性載體－C-G1與C-IG1，以NMR與 Mass確認成功合成出C-G1與C-IG1，亦經由螢光與吸收圖譜得知載體應保持香豆素原有之光學特性，為進一步確認，將C-Chol（載體前驅物）進行光致釋放實驗，同時探討載體對波長為365 nm及405 nm光的光敏感性。根據兩親性結構之特性，我們預測載體可於水中自組裝形成帶正電之微胞，並利用靜電吸引力攜帶DNA，因此我們利用Langmuir技術和Nile red assay探討載體分子於水中的聚集情形，以及其對UV光之光敏感性，除此之外，亦透過螢光滴定與溴化乙錠（EtBr）置換實驗研究載體對DNA的結合與光致釋放能力，而所得之實驗結果亦證實了我們的想法。現今已有許多文獻報導表示UV光會對人體組織造成傷害，因此我們希望能使用可吸收較常波長之光敏感載體，故我們設計並合成出（Carbazole-coumarin, CC）。不過迄今為止尚未有研究報導證實CC具有光致釋放的能力，因此我們合成出CC-Chol並對其進行一系列光致釋放實驗。而最終實驗結果證實CC具有光致釋放的能力。

關鍵字

香豆素 ； 光致釋放 ； 光控載體 ； Langmuir 單分子層 ； 咔唑－香豆素

並列摘要

With controlled drug release systems, a single dose can sustain drug levels within the desired therapeutic range for long periods of time. It avoid to administer drug frequently or continuously in order to achieve a long-lasting effect. The controlled drug release systems are applicable to almost every organ system, including the heart, brain, eye and peritoneum. It is also used to release a variety of therapeutic agents on different dimension scales, from proteins to DNA and RNA to small molecule drugs. Despite these advantages of drug release system, most had the shortcoming that drug release after administration was at best monotonic: drugs would be released at a predetermined rate irrespective of patient needs or changing physiological circumstances. They were “controlled” only in the sense that the encapsulating matrices affected, i.e., slowed, drug release. More recently, there has been increasing interest in developing methods where drug release can be controlled directly, triggered by either an interaction between a “smart” material and changes in its environment or by an operator, perhaps with a remote device affecting the injected or implanted drug delivery system. Ideally, such systems could determine the timing, duration, dosage, and even location of drug release, and could allow remote, noninvasive, repeatable, and reliable switching of therapeutic agent flux. Additionally, drug release in the “off” state should be minimal. Triggerable drug delivery systems enable on-demand controlled release profiles that may enhance therapeutic effectiveness and reduce systemic toxicity. Light is widely employed as a triggering stimulus in remotely triggerable drug delivery systems (RTDDS). Because light can be externally applied and easily tuned to a desired wavelength and power, it provides excellent spatial and temporal control over photoactive systems. Light's ability to activate chemistries on-demand independently of biological environments provides an enhanced level of control. Here, we employed coumarin as photosensitive group to synthesize the amphiphilic photosensitive carriers(C-G1 and C-IG1), which is composed of a lipophilic cholesterol and hydrophilic poly(amido amine) (PAMAM) dendron. The result products were characterized by NMR and Mass. First, we make C-G1 and C-IG1nder 365 nm and 405 nm light stimulation to further investigate the photolytic reaction of C-Chol. According to the results of photo-release experiment, C-Chol could effectively release cholesterol under 365 nm and 405 nm light stimulation. Next, the results of Langmuir and Nile red assay demonstrate that the amphiphilic structure allows the self-assembly into a core-shell-like pseudodendrimer with positive charge above the critical aggregation concentration (CAC) of approximately 40 μM, and C-G1 and C-IG1 is sensitive to 365 nm light. Additionally, the results of EtBr displacement assay shows that polycationic C-G1 and C-IG1can bind polyanionic circular DNA by electrostatic interaction forming stabile complexes and the complexes are readily dissociated under 365-nm light irradiation. It means C-G1 and C-IG1 could realease nucleic acids effectively under active 365 nm light stimulation. Because many endogenous molecules in human body both absorb and are degraded by UV light; the resulting damage and poor penetration limit the in vivo applicability of such materials. To improve the limits, we have synthesized Carbazole-coumarin(CC), having longer absorption wavelength. There are no papers confirm that CC will undergo photochemical reaction like coumarin, so we make CC-Chol irradiated by 365 nm and 405 nm light to further investigate the ability of C-Chol release cholesterol. In conclusion, we have successfully synthesized two amphiphilic photosensitive carriers(C-G1 and C-IG1), and will self-assemble into a core-shell-like pseudodendrimer with positive charge. Consequently, C-G1and C-IG1 can bind circular DNA by electrostatic interaction and effectively release DNA under 365 nm light stimulation. In addition, CC can undergo photochemical reaction like coumarin under 365 nm and 405 nm light stimulation.

並列關鍵字

coumarin ； photorelease ； photocarrier ； Langmuir monolayer ； carbazole-coumarin.

參考文獻

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