發炎誘發藥物釋放之產氣式中空微球系統及其相關治療

Controlled Release via Inflammation-Induced Gas-Generating Hollow-Microsphere Systems for the Treatment of Inflammatory Related Diseases

鐘敏帆(Min-Fan Chung)

指導教授 ： 宋信文

國立清華大學/工學院/化學工程學系/博士(2015年)

摘要

在現今骨髓炎的治療方面，如何讓藥物有效進入細菌生物膜是一個待克服的難題。盡管抗生素藥品不斷推陳出新，藥物穿透生物膜的效率仍比一般組織低，使得療程頻繁且漫長，並有較高的復發率。為發展更有效的治療方式，本研究是利用一具有「發炎控制」釋放效果之中空微球系統，以poly(lactic-co-glycolic acid) (PLGA) 為材料，利用微流道 (microfluidic device) 系統建立中空球殼 (core/shell) 結構，並於內部攜帶親水性藥物與產氣材料。當此中空微球處於發炎的微酸環境時，產氣材料會與氫離子或活性氧化物 (reactive oxygen species；ROS) 反應並產生氣體，進而脹破球殼，使球體內部的藥物能夠被釋放出來治療骨科相關疾病。本研究分為三部份來進行：第一部份是一具有「發炎控制」釋放效果之中空微球骨水泥系統。此中空微球內部攜帶親水性抗生素與NaHCO3，與骨水泥混合後注入骨髓炎患處，當此中空微球處於骨髓炎 (osteomyelitis) 的酸性環境時，NaHCO3會與氫離子反應而產生CO2氣體撐破球殼，達到藥物控制釋放效果。以兔子骨髓炎模型進行動物實驗，證明此藥物載體能達到良好的治療效果並減少復發機會。由於關節炎患部的酸性程度較骨髓炎輕微，第二部份我們利用此中空微球裝載乙醇、NaHCO3及類固醇藥物，來增加系統對發炎程度的敏感性。藉由患部發炎產生的活性氧化物將乙醇氧化成醋酸，並偕同患部中偏酸性的組織液，將中空微球內之NaHCO3反應分解產生二氧化碳氣體，以延伸應用於關節炎治療。第三部份，使產生的氣體除了能調控藥物釋放之外，亦能夠提昇藥物治療效果。我們把一氧化氮產氣材料(Diethylenetriamine NONOate) 及抗癌藥物CPT-11 共同包覆於中空微球內，藉由癌症部位偏酸性的組織液，與中空微球內之DETA-NONOate反應，使其分解產生一氧化氮氣體，反應後產生的一氧化氮氣體除了能撐破球殼並釋出CPT-11藥物之外，也能抑制P-glycoprotein(P-GP) 過度表現，來減少癌細胞抗藥性，使CPT-11能有效殺死抗藥性癌細胞。

關鍵字

發炎疾病 ； 刺激應答材料 ； 藥物釋放載體 ； 過氧化物 ； 一氧化氮 ； 抗藥性

並列摘要

Poly(D,L-lactic-co-glycolic acid) (PLGA) has been extensively utilized as a carrier material for drug delivery, but in the absence of a triggering mechanism, the rate of release of a drug from a PLGA-based carrier is typically slow, resulting in a sub-effective drug concentration. To address this issue, this work develops an injectable hollow microsphere (HM) system that carries the drug and the bubble-generating agent. Upon injection of this system into inflamed tissues, environmental protons (H+) or H2O2 infiltrate the shell of the HMs and react with their encapsulated bubble-generating agent to form bubbles that trigger localized drug release.
In study I, in the conventional treatment of osteomyelitis, the penetration of antibiotics into the infected bone is commonly poor. To ensure that the local antibiotic concentration is adequate, this work develops an injectable calcium phosphate (CP) cement in which is embedded pH-responsive HMs that can control the release of a drug according to the local pH. The HMs are fabricated using a microfluidic device, with a shell of PLGA and an aqueous core that contains vancomycin (Van) and sodium bicarbonate (SBC). At neutral pH, the CP/HM cement elutes a negligible concentration of the drug. In an acidic environment, the SBC that is encapsulated in the HMs reacts with the acid rapidly to generate CO2 bubbles, disrupting the PLGA shells and thereby releasing Van locally in excess of a therapeutic threshold. The feasibility of using this CP/HM cement to treat osteomyelitis is studied using a rabbit model. Analytical results reveal that the CP/HM cement provides highly effective local antibacterial activity. Histological examination further verifies the efficacy of the treatment by the CP/HM cement. The above findings suggest that the CP/HM cement is a highly efficient system for the local delivery of antibiotics in the treatment of osteomyelitis.
In study II, this work proposes an ultra-sensitive ROS-responsive HM carrier that contains an anti-inflammatory drug, an acid-precursor of ethanol and FeCl2, and a bubble-generating agent (SBC). In cases of osteoarthritis, in inflamed tissues H2O2 in low concentrations diffuses through the HMs to oxidize their encapsulated ethanol in the presence of Fe2+ by the Fenton reaction, to establish an acidic milieu. In acid, SBC decomposes to form CO2 bubbles, disrupting the shell wall of the HMs and releasing the anti-inflammatory drug to the problematic site, eventually protecting against joint destruction. These results reveal that the proposed HMs may uniquely exploit the biologically relevant concentrations of H2O2 and thus be used for the site-specific delivery of therapeutics in inflamed tissues.
In study III, Multidrug resistance (MDR) due to the overexpression of drug transporters such as P-glycoprotein (Pgp) increases the efflux of drugs and thereby limits the effectiveness of chemotherapy. To address this issue, this work develops an injectable HM system that carries an anticancer agent (CPT-11) and a nitric oxide (NO)-releasing donor (NONOate). Upon injection of this system into acidic tumor tissues, environmental protons (H+) infiltrate the shell of the HMs and react with their encapsulated NONOate to form NO bubbles that trigger localized drug release and serve as a Pgp-mediated MDR reversal agent. The site-specific drug release and the NO-reduced Pgp-mediated transport can cause the intracellular accumulation of the drug at a concentration that exceeds the cell killing threshold, eventually inducing its antitumor activity. These results reveal that this pH-responsive HM carrier system provides a potentially effective method for treating cancers that develop MDR.

並列關鍵字

inflammatory diseases ； stimuli-responsive materials ； drug delivery ； reactive oxygen species ； nitric oxide ； multidrug resistance

參考文獻

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