單基板液晶薄膜的蛋白質生物傳感及免疫檢測技術

Protein Biosensing and Immunodetection by a Liquid-Crystal Film Coated on a Single Substrate

白兆平(Chao-Ping Pai)

指導教授 ： 李偉 ； 李孟娟

國立交通大學/光電學院/影像與生醫光電研究所/碩士(2018年)

摘要

液晶生醫檢測技術在近年來之發展已趨於成熟，此技術的核心原理為藉由生物分子的附著，與液晶分子產生交互作用，造成液晶導軸的變化，於正交偏光系統下即可觀察到光學紋理的亮、暗訊號。有別於光訊號的定性分析，液晶生醫檢測的定量機制，其研發成果也不惶多讓，然而不論是定性法或是定量法，使用的量測樣品大多是傳統液晶盒，為液晶感測領域最常見的類型之一，但雙基板封盒結構的製程繁複，盒厚因子無法準確拿捏，而以往使用單基板結構的應用，大部分是作為液晶顯示器及光電元件，尚無人將之應用在生物感測上。

緣此，為了跳脫以往液晶與雙基板介面的窠臼，本論文欲將液晶旋轉塗佈於基板，以單基板液晶薄膜作為牛血清蛋白以及癌症生物標記CA-125免疫複合體之檢測，而旋轉塗佈參數的調整，可控制液晶膜之厚度，克服了以往液晶盒厚的不確定性。透過調整旋轉塗佈參數以及紫外光修飾配向層技術，可將牛血清蛋白之偵測極限降低至1 ng/ml；使用最佳轉速以及將感測液晶替換成高雙折射率之液晶，可將癌症生物標記CA-125免疫複合體之偵測極限往下拓展至10 ng/ml。

本論文除觀測向列型液晶的光學紋理做為定性分析，為了使單基板檢測平台更加完善，利用膽固醇液晶的可見光穿透譜特徵，在牛血清蛋白濃度為1 ng/ml-1 mg/ml的區間內，布拉格反射之中心波長λc隨著生物分子濃度增加而紅移，以及λc之穿透率會隨生物分子濃度增加而上升，以此機制作為系統之量化手段。

另外，本研究嘗試以反射中心波長在紅外波段的膽固醇液晶紋理結構，判斷生物分子的濃度區間，實驗結果顯示，當牛血清蛋白濃度為0 g/ml、1 ng/ml-1 μg/ml、10 μg/ml-10 mg/ml，其在偏光顯微鏡下之相態分別為垂直態、指紋態、平面態，並輔以穿透光譜之量測。綜合上述，本研究以單基板技術為基礎，建立新穎的液晶生物感測平台。

關鍵字

單基板 ； 液晶薄膜 ； 膽固醇液晶 ； 生物感測器 ； 牛血清蛋白 ； 免疫複合檢測 ； 癌症生物標記

並列摘要

Liquid-crystal (LC)-based biosensors have been completely developed in recent years. The main principle of this technique employs highly sensitive interfaces between LCs and the alignment layer to detect biomolecules and their interaction. We can observe the transitions of optical textures to receive qualitative signals through the reorientation of LCs in the presence of biomolecules. Quantitative analysis of this method for determining the biomolecular concentration has also been exploited. To date, the sample for measurements in most of LC-based sensors is prepared by confining the LC material between two substrates to constitute a sandwich-type cell. Such a cell geometry is however complicated and the cell gap factor cannot be accurately determined especially for a non-technical person. According to the recent researches, the applications of single-substrate structure are mostly used as LC displays and electro-optical devices, but no one has applied it on biosensing.

Applying the single-substrate technique for biodetection, in this research, bovine serum albumin (BSA) detection and cancer biomarker CA-125 immunoassay by a liquid-crystal film spin-coated on a glass substrate are demonstrated. The thickness of the LC film can readily be controlled by adjusting spin-coating parameters so that the uncertainty of the cell gap is overcome. By regulating spin-coating parameters and using UV-modified alignment layer technique, the detection limit for BSA can be extended to 1 ng/ml. When substituting a high birefringence LC as the sensing element, the detection limit of cancer biomarker CA-125 immunocomplex can be lowered to 10 ng/ml.

Apart from the use of optical texture observation for qualitative biodetection, the second part of this thesis is to use cholesteric LC (CLC) instead of nematic LC as the sensing platform and refers to its superior optical features for achieving quantitative analysis of biomolecular concentration. With increasing BSA concentration in the range of 1 ng/ml-1 mg/ml for the CLC-based biosensors with the central wavelength λc in the visible regime, it is found that the value of λc will get red-shift and the transmittance at λc will raise.

In addition, we further attempts to determine the concentration range of biomolecules by optical textures of the CLC whose λc is in the infrared region. Experimental results based on optical textures indicates that the BSA concentration can be ranged in terms of the CLC textures. The CLC is in the homeotropic in the case of 0 g/ml BSA but it is change to the fingerprint state and planar state when the BSA concentration is in the range of 1 ng/ml-1 μg/ml and 10 μg/ml-10 mg/ml, respectively. The change of CLC state as a function of BSA concentration can further be confirmed by measuring the corresponding transmittance spectra. As a result, this study is a novel LC biosensing platform through the instrumentality of a single substrate.

並列關鍵字

Single substrate ； Liquid-crystal film ； Cholesteric liquid crystal ； Biosensor ； Bovine serum albumin ； Immunoassay ； Cancer antigen 125

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