Harmonic Holographic Microscopy Using Nano-Materials as Imaging Probes

論文發表人:謝佳龍( 加州理工學院電機工程學系博士班)
 
http://www.cleoconference.org/

 

「發光標識物」一直以來受到生物科學界的重視，因為透過適當的化學方法，這些「發光標識物」可以準確的標記在希望觀察的目標物上，使我們得以看到原本看不見的目標物的分佈。螢光標識物，例如綠螢光蛋白以及量子點，具有高亮度以及生物體相容的優點，所以已經被廣泛的使用。然而他們確有著光性質不穩定的缺點。我們提出使用從奈米粒子中產生的光二倍頻作為訊號的想法，希望藉此來取代螢光訊號。因為光二倍頻的機制中並沒有真實的能階躍遷，所以光二倍頻訊號是非常穩定的。除了穩定之外，光二倍頻擁有飛秒等級的快速產生機制，這讓我們有機會看到目標物的快速動態資訊。此外，當使用這些二倍頻奈米粒子作為發光標識物時，我們可以更好的方法來偵測他們。利用光二倍頻的同調性質，我們可以用全像術的技術來存取光二倍頻訊號。全像術的技術可以在一張影像中同時捕捉光的強度和相位。利用數位分析所取得的影像後，一張影像便可捕捉二倍頻標識物的三度空間分佈。在這篇論文中，我們分析光二倍頻奈米粒子的光學特性以及發展倍頻全像顯微術。二倍頻奈米粒子的三度空間分佈成功的被紀錄在一張二維影像之中。

 

Luminescent markers have attracted lots of attention in bio-science. With proper functionalization, these markers could be attached to the target of interest and make the target visible. Fluorescent bio-markers, such as green fluorescent protein or quantum dots, have been popularly used due to their outstanding brightness and biocompatibility. However they suffer from the deficiency of photo-stability. We introduce the idea of using second harmonic generation (SHG) from nanoparticles as the signal. These nanoparticles can be used as markers to label biological cells and allow for better detection techniques. In contrast to fluorescent markers, both limited by photobleaching, Second Harmonic Radiation IMaging Probe (SHRIMP) emits a stable signal owing to the lack of real energy state transition. The femtosecond response allows for observing fast dynamic process, such as protein conformation. Moreover the coherent nature of SHG enables us to record holograms at the doubled optical frequency. Since the hologram captures both amplitude and phase information of the optical fields, we could reconstruct the three-dimensional (3D) object field from one hologram. We demonstrated the harmonic holographic microscopy which captures 3D distribution of SHRIMP in one image.