飛秒雷射於生物分子成核與奈米粒子捕陷之研究

Abstract

我們探討飛秒雷射的三項新穎現象：飛秒雷射誘發結晶化、飛秒雷射促進類澱粉蛋白纖維化與飛秒雷射捕陷單一奈米粒子。這些探索性研究主題在飛秒雷射於分子科學與科技上具有高度潛力。 於結晶化實驗中，我們首先藉由飛秒雷射誘發胺基酸之結晶化釐清飛秒雷射參數如何影響結晶化機率與所得結晶等實驗結果，發現照射僅一發雷射脈衝於氣液界面即有機會可形成單一結晶。於第二部分，因結晶化與類澱粉蛋白纖維化皆具有成核的依存性，於是我們的興趣延伸至飛秒雷射於類澱粉蛋白纖維化之應用。透過使用胰島素，我們檢驗類澱粉蛋白纖維化如何被飛秒雷射參數與溫控條件所影響。我們觀察到樣品預熱與短暫的雷射照射可加速類澱粉蛋白纖維化，如其成核所需時間被縮短。這是首次示範照射飛秒雷射可促進類澱粉蛋白纖維化。 於第三部分，我們研究單一粒子於連續波或飛秒雷射捕陷下的動態。事實上，在關於連續波與飛秒雷射捕陷效率的文獻中有以下矛盾的敘述：奈米粒子可在飛秒雷射捕陷下被有效捕捉，但捕捉微米粒子的效率卻在連續波與飛秒雷射捕陷下並無顯著差異。於是我們統計性地量測500奈米大小粒子的滯留時間－對應到單一粒子在雷射捕陷下可被穩定捕捉多久。我們發現此特定大小的粒子在連續波雷射捕陷下會隨雷射功率增加而延長被捕捉的時間；而在高功率的飛秒雷射捕陷下粒子卻無法被穩定捕捉。此發現提供對光操控有更深入的理解：目標粒子的動態與粒子大小、雷射模式與雷射功率有依存性。

We studied femtosecond (fs) laser-induced novel phenomena; fs laser-induced crystallization, fs laser-enhanced amyloid fibril formation and fs laser trapping of a single nanoparticle as exploratory topics showing high potential of fs laser in molecular science and technology. In crystallization experiments, we firstly clarified how fs laser parameters affect experimental results including crystallization probability and obtained crystals by crystallizing glycine, and found that one single crystal could be possibly formed by irradiating only a single pulse at the air/solution interface. Next, our interests were extended to amyloid fibril formation since both crystallization and amyloid fibril formation are nucleation-dependent. By utilizing insulin, we examined how amyloid fibril formation was affected by fs laser parameters and incubation conditions. We observed that pre-incubation and short laser irradiation accelerated amyloid fibril formation as its nucleation time was shortened. It is the first demonstration that fs laser irradiation can enhance amyloid fibril formation. In the third part, we studied dynamics of individual single particles under laser trapping in either cw- or fs-mode. In fact, there is a crucial contradiction between cw and fs laser trapping efficiencies reported; remarkable trapping efficiency for nanoparticles under fs laser trapping but indistinguishable trapping efficiency for a single microparticle with cw or fs laser. Accordingly, we statistically measured immobilization time of individually trapped 500-nm-sized particles indicating how long a single particle of intermediate sizes can be stably immobilized under laser trapping. It is found that particles in this particular size could be trapped longer as laser power increased under conventional cw laser trapping; however, the particles could not be stably trapped under fs laser trapping at high laser power. This finding provides a deeper understanding for optical manipulation that the dynamics of the target particle is size-, laser mode-, and laser power-dependent.