利用金奈米粒子結合表面輔助雷射脫附游離法偵測 核苷單磷酸

Abstract

本論文利用溴化十六烷三甲基銨 (cetyltrimethyl ammonium brombide, CTAB吸附在金奈米粒子 (gold nanoparticles, Au NPs) 表面當做選擇性探針，同時也作為表面輔助雷射脫附游離質譜法 (surface-assisted laser desorption/ ionization mass spectrometry, SALDI-MS) 之無機基質，應用於食品工業及生物樣品中核苷單磷酸 (monophosphate nucleotides) 之偵測。由於腺核苷單磷酸 (adenosine 5’-monophosphate, 5’-AMP) 、鳥核苷單磷酸 (guanosine 5’-monophosphate, 5’-GMP)、尿核苷單磷酸 (uridine 5’-monophosphate, 5’-UMP) 和胞核苷單磷酸(cytidine 5’-monophosphate, 5’-CMP) 等分子帶負電，可藉由靜電作用力和帶正電的CTAB結合，使其更接近Au NPs表面並導致Au NPs聚集。藉由離心的方式濃縮分析物樣品，即可直接以SALDI-MS進行偵測。研究結果顯示CTAB除了可抑制背景雜訊，亦可增加訊號解析度及強度。其最佳化條件為使用1.8 nM Au NPs與0.4 μM CTAB混合所配製出的CTAB-Au NPs作為SALDI-MS之無機基質，可測得溶液中5’-CMP、5’-UMP、5’-AMP和5’-GMP之偵測極限分別為25、25、5和10 nM (雜訊比為3時)。在真實樣品方面，香菇萃取物及味精中核苷單磷酸的檢測結果與相關文獻一致。本方法提供很好的靈敏度、再現性 (變異數小於20%) 及樣品處理簡單的優點，希望此技術將來能應用在生物系統中核苷單磷酸代謝機制的研究上。

This thesis is that we demonstrated the determination of monophosphate nucleotides through the surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using hexadecyltrimethylammonium bromide (CTAB) adsorbed gold nanoparticles (CTAB-Au NPs). The binding of four monophosphate nucleotides — adenosine 5’-monophosphate (5’-AMP), guanosine 5’-monophosphate (5’-GMP),uridine 5’-monophosphate (5’-UMP) and cytidine 5’-monophosphate (5’-CMP) — to the surfaces of these CTAB-Au NPs induced their aggregation, which allowed selective concentration of the four analytes from sample solutions. The analytes adsorbed CTAB-Au NPs were directly subjected to SALDI-MS measuremen, preventing a need of mixing the analytes with organic matrices. Our results revealed that CTAB was effective to improve ionization efficiency of the analytes and to suppress the MS background from Au clusters. By using CTAB-Au NPs that were prepared by mixing 0.4 μM CTAB with 1.8 nM Au NPs, our SALDI-MS approach provided the detection of limits at a signal-to-noise ratio of 3 of 25, 25, 5 and 10 nM for 5’-CMP, 5’-UMP, 5’-AMP and 5’-GMP, respectively. We have successfully validated the practicality of this approach through the analyses of 5’-AMP, 5’-GMP, 5’-UMP and 5’-CMP in the mushrooms extracts and of 5’-GMP in monosodium glutamate. Our approach provides advantages of simplicity, sensitivity, and reproducibility (shot-to-shot variation less than 20%) for the the determination of the concentrations of the analytes in the biological samples。