高速螢光影像於超音波激發相變液滴藥物釋放之研究

High-Speed Fluorescence Imaging of Ultrasound-Triggered Drug Release from Phase-Change Droplets

張宗倫(Chang, Tsung Lun)

指導教授 ： 葉秩光

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2015年)

https://doi.org/10.6843/NTHU.2015.00276

摘要

新式超音波藥物載體—相變液滴，外部為脂質殼層，可乘載多種抗癌藥物、內部為液態全氟化合物，於體內可以穩定存在，可透過聲學激發液滴汽化(Acoustic Droplet Vaporization，ADV)進行藥物釋放，對於藥物傳遞相當具有潛力。然而，目前並沒有任何文獻關於相變液滴於瞬間的藥物釋放動力學，這是由於ADV的過程僅為微秒等級，且於傳統白光視野下難以觀察藥物。因此，本研究目的是透過架設一套高速螢光顯微系統，可使得相變液滴於ADV瞬間的藥物動態視覺化，並探討藥物脫離相變液滴的原因、脫離後的藥物於空間上的分佈、以及聲學參數對於釋藥距離、以及釋放量的影響，進而藉此解開相變液滴的藥物釋放機制。
相變液滴的藥物釋放必須高於特定強度的聲學參數(至少9 MPa)才會啟動。而相變液滴的釋放特徵方面，本研究發現所釋放的藥物主要累積於相變液滴與環境的接觸面，這也暗示了相變液滴作為標靶治療的潛力。相變液滴的釋放機制以超高速螢光進行攝影，探討聲學參數對於螢光影像的差異，且透過程式使得影像特徵數值化後，發現聲壓對於脂質動態分佈移動幅度具有正相關、12 MPa所造成的移動幅度為8 MPa的3.09倍，推測是因為具有方向性的匯聚流場所影響，並以白光拍攝相變液滴汽化之粒徑變化，證實氣泡的劇烈震動為流場形成的關鍵、12 MPa所造成的氣泡脹縮幅度為8 MPa的3.61倍。綜合上述可解開相變液滴的藥物釋放機制 : 透過聲學激發液滴汽化後，氣泡劇烈脹縮引發具方向性的流場，使得脂質交互擠壓，進而連帶著脂溶性藥物脫離載體。最後探討粒徑與聲壓對於釋放影響，發現不論是在釋放量、抑或釋放距離，粒徑越小或聲壓越高的組別，皆展現出相對較高的效率，並再度透過高速攝影液滴汽化之粒徑變化，證實氣泡脹縮的幅度為影響釋放效率的主因。

關鍵字

相變液滴 ； 聲學激發相變液滴汽化 ； 藥物釋放

並列摘要

The new ultrasound drug carrier, phase-change droplet (PCD), with liquid perfluorocarbon in lipid shell, and steady in the circulation, was proposed by R. E. Apfel in 1998. PCDs were promising for local drug delivery due to their ability to undergo acoustic droplet vaporization (ADV) under ultrasound excitations. However, no study has investigated the transient dynamics of drug release, since ADV occurred on microsecond scale and drugs were hardly identified in conventional bright field microscopy. Here, we established a high-speed fluorescence imaging system to visualize the process of drug release during ADV. The aim of the study was to find out the way of drug release from PCDs, the distribution of the released drug, the effect between acoustic parameters and release number, and finally the mechanism of drug release from PCDs.
Drug release from PCDs must be triggered by acoustic parameter higher than specific level (at least 9 MPa). At the pressures higher than ADV threshold, the shedding drug were observed only on contacted wall between droplets and tube. To figure out the mechanism of drug release from PCDs, the process was captured by high-speed fluorescence imaging system. From quantified images, acoustic pressure had effect on lipid dynamic on bubble shell, which was resulted from directionally converging flow. Moreover, the bright-field images were quantified to verify the effects of the evolution of bubble resulting in converging flow. In summary, the mechanism of drug release from PCDs was that ADV triggered the evolution of bubble, which resulting in converging flow. The flow induced the effect of lipid bending and shedding with drugs. Finally, small PCDs or high pressure induced the high efficiency on either release number or release distance. Through high-speed images, it was proved that the release efficiency was related to evolution of bubble.

並列關鍵字

phase-changed droplets ； acoustic droplet vaporization ； drug release

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