石墨烯的霍爾效應感測器應用於快速且無標記DNA之研究;The study of graphene-based Hall-effect biosensors applied to rapid and label-free DNA

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Title:	石墨烯的霍爾效應感測器應用於快速且無標記DNA之研究;The study of graphene-based Hall-effect biosensors applied to rapid and label-free DNA
Authors:	吳緯振;Wu, Wei-Cheng
Contributors:	機械工程學系
Keywords:	石墨烯;無標記DNA;霍爾效應
Date:	2022-06-15
Issue Date:	2022-07-14 01:21:09 (UTC+8)
Publisher:	國立中央大學
Abstract:	目前透過化學氣相沉積法於金屬基板上合成大面積石墨烯並將其轉印至絕緣基板製備成生醫感測器已是成熟的技術，藉由石墨烯優異的電學特性(極高的導電性以及載子遷移率)可作為生醫感測元件的主要平台。此外由於石墨烯表面之π軌域電子容易與DNA之苯環結構重疊並產生π-π堆疊，因此在現今生醫感測應用上可結合無標記且無官能化改質的優點於簡易感測流程。然而現今常用之石墨烯生醫感測元件皆有所瓶頸，如常見的螢光式的感測方式需要螢光分子進行標記，製備上較為繁瑣;以及液體式閘極(liquid-gate)場效電晶體(field-effect transistor, FET)，雖然其能快速且精準擁有檢測結果，但目前研究中發現液體式閘極FET上產生的電雙層會造成電容屏蔽影響檢測準確度。因此開發一種無標記並能解決電容屏蔽影響之檢測方式為目前石墨烯生醫感測研究上首要解決之問題。此外石墨烯為受電荷轉移或靜電效應的作用影響於目前文獻中對其檢測機制仍尚未明確。而DNA與材料間產生靜電排斥導致無標記石墨烯感測器整體所需的感測時間較長也是目前相關研究極需解決之難題。本實驗利用CVD大面積成長之單層石墨烯於製備生醫感測元件與病毒DNA序列上的苯環π-π堆疊，實現無標記檢測人類皰疹病毒第四型(Epstein-Barr Virus, EBV)之DNA序列，並透過霍爾量測有效避免FET中金屬閘極上電雙層產生的電容屏蔽之影響。此外也針對DNA序列對整體石墨烯以及其表面上造成的影響進行探討，並利用電泳吸附所產生的電場解決靜電排斥造成需耗時的感測程序。研究結果透過霍爾效應搭配電泳吸附的量測線性範圍為1 pM至10 nM、檢量限為1 pM且線性回歸達0.94，顯示此基於石墨烯的霍爾效應感測器對於EBV DNA具有高的感測效能。此外，透過新穎的表面界達電位(Surface zeta potential)分析石墨烯表面和吸附探針與目標DNA的過程，電位從-24.47降低至-33.05 mV，證實DNA序列於石墨烯表面上的電荷積累現象，建立感測機制的探討。利用電泳吸附的方式大幅降低DNA與石墨烯間以及探針DNA與目標DNA間靜電排斥的影響，因此從18個小時大幅縮短整體感測時間至大約5分鐘。;With excellent electrical properties such as high electrical conductivity and carrier mobility, large-area graphene grown by chemical vapor deposition (CVD) technology, which was widely used as the sensing material of bio-sensing platform. By forming a π-π bonding between graphene and the benzene structure of DNA, a label-free and non-functionalized graphene could be realized by use of graphene as the platform material which could significantly simplify the process of the currently used bio-sensing applications. However, several issues such as the cumbersome preparation of fluorescent sensing, the affected detection accuracy of liquid-gate field-effect transistor (FET) due to the formation of double layer capacity, and the relatively long sensing time caused by the electrostatic repulsion between graphene and DNA were still remained and need to be solved urgently. As for the detection mechanism, considering the complex affection of charge transfer and electrostatic effect of graphene, related kinds of literature were still lacking and further research was needed to be clarified. In this study, a label and functionalize-free graphene-based Epstein-Barr Virus (EBV) DNA sensing device was prepared by the CVD method and followed by the Hall measurement, which could effectively avoid the affection of voltage consumption due to the double layer capacity. In addition, the detection mechanism was further explored and investigated by the measurement of surface charging. Moreover, the electrophoretic adsorption method was introduced to solve the electrostatic repulsion issue. The research results show that with the electrophoretic adsorption, the effective sensing range from 1 pM to 10 nM was achieved together with a low detection limitation of 1 pM and the high reliability of 0.94. Moreover, for the first time, a novel surface zeta potential measurement was used to investigate the conditions of charging accumulation after the immobilization of probe DNA and the hybridization of target DNA, ranging from -24.47 to -29.42 and -33.05 mV, respectively. This could help to explain the sensing mechanism in this study Also, electrophoretic adsorption is used to reduce the influence of electrostatic repulsion between DNA and graphene and probe DNA and target DNA by shortening the sensing time from 18 hours to about 5 minutes.
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