探討螢光奈米鑽石載體對細胞代謝之影響

Abstract

螢光奈米鑽石是大小位於奈米層級的鑽石顆粒，通過高速粒子束的撞擊後再以熱能結合創造出晶格缺陷。由於其特殊的晶格結構，螢光奈米鑽石在約 560 nm 波長的光激發之下，可以發出波長約 700 nm的紅色的螢光。螢光奈米鑽石的螢光具有高穩定性，在組織中穿透深度高等特性，且無光漂白、光閃爍的缺點。文獻指出，螢光奈米鑽石不具生物毒性，與其他碳結構之奈米材料相比亦具有較佳的生物相容性。同時奈米鑽石的表面易於做官能基的修飾，便於更進一步以生物分子如核酸或蛋白質等做結合。許多研究指出螢光奈米鑽石於生醫領域的應用有高度潛力，如運載藥物分子或做為細胞標定的探針。為了評估並優化螢光奈米鑽石於臨床上的運用，進一步深入了解奈米鑽石顆粒對細胞的交互作用與影響是必要的。以做為基因治療之藥物載體為例，奈米鑽石需要進入細胞內釋放搭載的核酸藥物以達到治療的效果。然而螢光奈米鑽石對於細胞內部的影響，目前還尚不清楚。在本研究中，我們利用口腔癌細胞株為研究模式，詳盡的探討細胞在吞入螢光奈米鑽石顆粒後受產生的變化。我們發現細胞攝入螢光奈米鑽石後，細胞的增生會更加活化；同時細胞主要代謝途徑中的醣解作用與粒線體有氧呼吸效率也受到提升。我們並使用代謝體輪廓分析之技術來鑑別導致此現象之可能相關代謝途徑；而實驗顯示醣解作用路徑之代謝流通量降低，而乳酸生成和胺基酸之生合成的胞內代謝物水平有所增加，可能代表著更多碳源的利用自能量產生導向生合成的途徑。這些結果或許是由於細胞將攝入之螢光奈米鑽石誤認為如碳水化合物之營養物，進而導致胞內的代謝流向改變。我們將更進一步釐清細胞受到影響的分子層面之機制，而未來也可以將螢光奈米鑽石在促進細胞增殖與活化細胞代謝之特性於運用臨床治療的設計；把奈米鑽石與標靶於特定細胞代謝途徑或針對細胞分裂之藥物作結合使用，以提升治療的效果，實現多功能奈米載體在癌症治療的應用。本研究探討螢光奈米鑽石對細胞之細部影響，揭露了奈米鑽石運用於生醫領域的全新觀念：奈米鑽石不但具有作為藥物載體之潛力，其與細胞之交互作用或許可以輔助藥物運作以提升治療效果或降低副作用。

Fluorescent nanodiamonds (FNDs) are nanometer scale diamond particles bearing incandescent fluorescence, and can be easily functionalized with chemical groups and bio-molecules. Several studies have reported that FNDs display better biocompatibility than most of the other carbon-based nanomaterials. In our lab, we have previously demonstrated that FNDs promote delivery of siRNA into cancer cells to enhance target gene suppression. Together, these properties illustrate FNDs as an ideal candidate nanovector for cancer therapy, with potential to combine imaging, targeting, and enhanced delivery into cancerous tissues. Toward the optimization and evaluation of FNDs as clinically applicable biomedical carrier, it is obligatory to understand the detailed interactions between cells and FND, an issue that remains largely obscure. In this study, we use oral cancer cell models to monitor cellular interactions with FNDs upon their delivery as drug carriers. We found that FND-internalized cells display enhanced proliferation compared to untreated control cells. This was accompanied with increasing oxygen consumption as well as anaerobic glycolysis, suggesting a major change on cellular metabolism. To understand how FND evoke this metabolic change in cells, we employed metabolomic methodology to identify the putative signaling pathways underlying this response. Our data revealed an increasing glycolytic flux into lactate production also amino acid and lipid anabolism, suggesting an increased tilt of carbon sources utilization towards biosynthetic pathways. This unprecedented effect of FND implies the possibility of cells to uptake FNDs in view of mistaking FNDs as nutrients, which leads to subsequent change in cell metabolism. Furthermore, we can make use of the metabolic and proliferative change induced by internalizing FNDs to drug delivery applications by combining anti-cancer drugs specifically against metabolism or cell division. Understanding the cellular response to FND reveals a new aspect of FND in drug delivery. FND has the potential not only being a vehicle transporting drugs, the interaction of FND and cells itself can be used to help improve therapeutic outcomes.