- 學位論文
從中藥合成之碳量子點作為藥物載體與生物顯影之應用
Application of Carbon dots Synthesized from Traditional Chinese Medicine as Drug Carrier and Bioimage
摘要
碳量子點是一種泛指直徑小於10nm的新興奈米碳材料，可經由不同程序合成，包括水熱法、微波、高壓加熱，使用不同的有機前驅物製備，可得到表面含有不同官能基的碳量子點，使其具有多元化學特性。 碳量子點易於製備及修飾，有許多優異的生物及化學特性，生物特性像是高度水溶性、無毒、生物相容性佳；化學特性像是高度螢光效應、抗光漂白現象等。 目前對於碳量子點與醫藥結合的應用相當多，本篇研究著重在提升傳統化療藥物對癌細胞的選擇性，藉此提升藥效，達到降低劑量與減少副作用的目標。 使用傳統化療藥物治療癌症最大的缺點在於副作用。目前傳統藥物對癌細胞的作用方式多為抑制細胞生長，藉由競爭性抑制特定酵素作用，中斷細胞的合成或代謝路徑，來抑制細胞生長，由於傳統化療藥物無法有效識別癌細胞與正常細胞，所以使用傳統化療藥物的同時也會傷害正常細胞，導致嚴重副作用像是掉髮、貧血、腹瀉、噁心嘔吐、疲憊虛弱、免疫力降低、消化道損傷等。 一般在使用傳統化療藥物進行化療時，藥物劑量若要有效抑制癌細胞必須使用高劑量，但使用高劑量的同時對正常細胞的傷害過大，所以只能選擇中低劑量給予，同時適度補充拮抗劑，且療程必須結合其他治療方式，像是放射線治療或外科手術切除腫瘤。 改善傳統藥物製造嚴重副作用的其中一種方式是使用藥物載體，藥物載體的概念是在載體上修飾配體與攜帶藥物，配體能夠與癌細胞膜上的特定受體結合而使此藥物載體聚集在癌細胞附近，之後再配合有效的釋放系統釋放藥物，達到對癌細胞的選擇效果。 本篇研究使用從川芎(Ligusticum striatum)合成的碳量子點作為methotrexate的藥物載體，methotrexate為結構類似葉酸的傳統化療藥物，與葉酸受體的親和力為葉酸對葉酸受體的1000倍，葉酸受體（FR）在大量癌細胞中過度表達而成為公認的腫瘤細胞生物標誌物。 Methotrexate會競爭性結合葉酸受體與二氫葉酸還原酶，進入葉酸循環中干擾癌細胞對葉酸的攝取及嘌呤嘧啶的合成，進而破壞DNA/RNA的合成，達到抑制細胞生長的作用。利用methotrexate與葉酸受體的高度親和力，將methotrexate以靜電作用力附著在碳量子點上，用碳量子點作為methotrexate的載體運輸藥物，由於癌細胞具有旺盛的乳酸代謝途徑，所以周遭環境在乳酸堆積下呈現弱酸性，弱酸環境中可以促進搭載藥物的碳量子點釋放藥物，癌細胞附近的methotrexate濃度將會選擇性的提高，達到同時降低藥物劑量與提升藥效的目的。
並列摘要
Chemotherapy is a kind of cancer treatment that uses chemotherapeutic drugs to kill fast-growing cancer cells. Generally, chemotherapeutic drugs producing cytotoxic effects on cancer cells while simultaneously may be able to damage the normal healthy cells, resulting in side effects. This is a major disadvantage of using traditional chemotherapeutic drugs in the treatment of chemotherapy. To overcome this significant issue, the drug delivery systems are developed that demonstrating their superior efficiency towards loading and releasing of drugs, and targeting cancer cells. Recently, carbon dots (C-dots) are a promising material for the development of biosensors and drug delivery systems due to their good biocompatibility and low toxicity. Herein, we report the fabrication of C-dots with methotrexate (MTX) to investigate the drug-carrying capability of C-dots for delivery of MTX and their therapeutic activity. The C-dots was synthesized from ligusticum striatum Chinese medicine and used as drug carrier. MTX is a traditional chemotherapeutic drug whose structure is similar to folic acid. The MTX was conjugated with C-dots through electrostatic interaction. The capability of drug-loading and releasing of C-dots/MTX was performed, and the results revealed a high drug-loading capability of C-dots. The C-dots/MTX exhibited pH-dependent MTX release behavior in which high efficiency obtained at pH 5.0 compared to that of pH 7.4. The cell viability of C-dots and C-dots/MTX was determined in HeLa and human normal fibroblasts cells. The C-dots possess less toxicity whereas C-dots/MTX showed high cytotoxicity compared to that of bare MTX on HeLa cells. This finding confirms that the C-dots/MTX had a higher cellular uptake which signifying excellent drug-carrier property of C-dots. In addition, the fluorescence bioimaging measurements were examined in live HeLa cells to verify the drug-delivery efficacy of C-dots/MTX by using confocal fluorescence microscopy. Overall, the C-dots/MTX promises their potential in bioimaging and drug-delivery system resulting from the fascinating features including photoluminescent, good biocompatibility, cellular uptake, and efficient drug release properties. It should be believed that the C-dots/MTX nanodrug may hold great potential for cancer chemotherapeutic applications.