Biotin-Streptavidin 生物分子感測

首先製作了奈米線蕭特基二極體，並在其中加入金屬之參考電極，目的為維持平衡 溶液中之電壓，並可在溶液中加入電壓比較元件對於帶電溶液之感測靈敏度。元件完成 後，將在中間元件部份接上微流道，目的在使溶液只流經元件的部份，而不會影響左右 電極的電性量測。下圖即為量測Biotin-Streptavidin 生物分子之元件光學顯微鏡俯視圖:

圖3-28、加入參考電極與微流道之元件光學顯微鏡俯視圖。

圖 3-29 即為當參考電極(VG)為-025~0.25 伏特時所得到之兩種元件電流電壓特性 圖。由圖可見，在奈米線蕭特基二極體順向偏壓(VD>0)電流的部份，電流受參考電極電 壓影響之變化差異不大，但奈米線蕭特基二極體之逆向偏壓的部份(VD<0)，電流受參考 電極電壓影響之變化明顯許多。由此可推測，當元件於溶液中感測帶電生物分子之時，

奈米線蕭特基二極體逆向偏壓電流之感測靈敏度可能較高。

此後，我們對兩種元件表面作 Biotin-Streptavidin 生物分子之修飾，並在修飾 Streptavidin 之前後作電性之量測，結果如下圖︰

圖3-30、元件表面修飾Biotin-Streptavidin電流電壓特性圖。

奈米線蕭特基二極體之生物感測器，主要即是利用對奈米線之表面做特定之修飾 後，接上特定之帶電微小物質，而形成類似一個上電極的結構。奈米線上的載子密度 (Carrier Density)，受到表面接著分子(例如:DNA 或是蛋白質)所帶電荷的影響，依據固態 物理理論其載子會被 Depletion 或 Accumulation，進而改變奈米線的電導值。本次論文 實驗所製作的元件皆為N 型矽，因此若接上奈米線之物質帶負電，則等效於對元件加上

此次 Biotin-Streptavidin 系統中，Biotin 為帶正電荷的物質，而 Streptavidin 則是帶 負電分子。由圖3-30 可見，由於 Streptavidin 帶負電，而本實驗所製作的元件參雜皆為 n-type，因而當 Streptavidin 接上元件時形成類似一個上電極的結構，則等效於對元件加 上一上電極之負電壓，將造成元件電流之下降。

表3-3、元件表面修飾Biotin-Streptavidin導電度變化量表。

+1 V -1 V

25pM 5% 5.35%

250nM 5.66% 142%

為了準確計算感測靈敏度，所以取元件操作於 VD=-1 和 1 伏特時所量測的電流值 來做計算。表3-3 與圖 3-30 相對應，為計算奈米線蕭特基二極體在兩種 Streptavidin 濃 度下的感測靈敏度。當所修飾的Streptavidin 為濃度 25 pM 時，元件操作在逆偏 VD=-1 V 之導電度變化量ΔG=5.35%，而在順偏 VD=1 V 之導電度變化量 ΔG=5%；Streptavidin 濃 度為250 nM 時，元件操作在逆偏 VD=-1 V 之導電度變化量 ΔG=142%，而在順偏 VD=1 V 之導電度變化量ΔG=5.66%。證明奈米線蕭特基二極體操作在逆向偏壓的感測靈敏度是 較高的。

第四章 結論與未來展望

(Summary and Future Work)

4.1 結論

4. 無論是在 AEAPTMS-GNP 或是 Biotin-Streptavidin 之系統下，奈米線蕭特基二極體皆 可成功的感測到帶電之分子，而且感測之靈敏度相當高。

是未來所必要的。

3. 利用蕭特基二極體來感測其他不同之生物分子，如 DNA。

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