本實驗利用螢光共振能量轉移現象，來觀察包覆於奈米微粒載體內之doxorubicin於細胞內不同胞器的釋放情形。其原理為利用螢光共振能量轉移現象對於donor與acceptor間距離非常敏感之特性，當N-palmitoyl chitosan ( NPCS )奈米微粒進入不同酸鹼值的胞器時，隨著pH值的降低，接枝在其自由胺基上的螢光物質Cy5 ( acceptor )與包覆於疏水鏈段內之doxorubicin ( donor )兩者間的距離會逐漸拉開，造成螢光共振能量轉移現象的變化。由實驗結果得知，奈米微粒主要是藉由caveolae-mediated endocytosis進入細胞。最初奈米微粒位在caveosome ( pH 7.0 )，此時doxorubicin包覆於奈米微粒載體內，可觀察到強烈的螢光共振能量轉移現象。接著，隨著奈米微粒逐漸進入early endosome ( pH 6.2 )， doxorubicin與Cy5間的距離隨pH值降低而逐漸拉開，螢光共振能量轉移現象開始減弱。之後奈米微粒進入late endosome / lysosome ( pH 5.0 )，螢光共振能量轉移現象消失，僅顯現出doxorubicin的螢光，且doxorubicin釋放量有隨時間增加的趨勢，表現在細胞核內的doxorubicin螢光也漸漸增強。實驗最後再輔以MTT assay來測試細胞的存活率，結果顯示出Cy5 labled NPCS15%-DOX奈米微粒對於腫瘤細胞確實具有治療效果。

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