奈米粒子協助超音波治療的機制探討 -不同奈米粒子數量與空穴效應

Abstract

奈米粒子協助超音波治療(NAUT)為一新型態的腫瘤治療方式，研究發現將奈米粒子加入培養皿與細胞一起培養，隨後給予中等能量超音波照射，超音波傾向殺死癌細胞而保留正常細胞功能。預期將可有效降低傳統癌症治療為人詬病的副作用發生。然而其能夠選擇性針對癌細胞毒殺背後的機轉仍不清楚。本篇研究以奈米粒子能否作為反應核(nucleation sites)，降低空穴效應閾值，進而增加空穴效應，方面進行假設。利用Weissler reaction的方式來量化空穴效應，調查於溶液中加入不同數量的奈米粒子能否增加空穴效應的發生。實驗初期我們使用奈米金粒子做為奈米材料，然而發現我們所使用的碘化鉀試劑有其限制所在，會與加入的奈米金粒子發生反應進而干擾實驗結果。隨後改用奈米聚苯乙烯粒子觀察與空穴效應之間關連性，結果發現含有奈米聚苯乙烯組別與沒有加入任何奈米粒子組別所記錄到的三碘離子訊號量之間並無顯著差異，也就是說奈米粒子的加入無法直接增加空穴效應的產生。NAUT治療背後機制可能是超音波熱效應或其他機械效應所致，而非空穴效應，實際機轉待後續進一步調查。

Currently cancer therapies have serious side effects which are largely due to the destruction of normal cells. The immune system and normal organ functions can be compromised by these treatments which is why many cancer patients die. There is a need for methods in cancer treatment that reduce the destruction of normal cells which nanoparticle-assisted ultrasound for cancer therapy (NAUT) may do. Low to medium power ultrasound can kill cancer cells preferentially over normal cells in the presence of nanoparticles, but the mechanism for such is not clear. So we examined the cavitational aspects to determine whether increased cavitation is responsible for NAUT in order to optimize it. In this present investigation, the effect of the number of nanoparticles on cavitation activity has been determined by the Weissler reaction, which measurs and quantifies inertial cavitation. Originally we used gold nanoparticles as the nanomaterial, but the reaction is subject to two limitations (aggregation and reaction) and is not suited for monitoring gold nanoparticle suspensions. Using polystyrene nanoparticles, results show that triiodide (I3-) signal (the measure of inertial cavitation) in the potassium iodide assay was not significantly different among suspensions containing different numbers of polystyrene nanoparticles. The mechanism of NAUT for the enhanced difference in cell destruction may be heat or other mechanical effects rather than acoustic cavitation.