質譜法在化學反應監測及快速檢測致病細菌之發展及應用

Abstract

質譜法可以被用來確定分析物的分子量和分子結構，具有強大的分析功能，尤其大氣壓下質譜法在21世紀初的快速發展使得質譜游離法的進展相當快速。此大氣壓下質譜游離法的優點為可以以最少的樣品前處理步驟，甚至是可以在不用任何樣品前處理的的情況下直接進行質譜分析。而大氣壓下質譜游離法的發展中的一個主題為所謂的反應型質譜法即以反應物為樣品而在樣品游離的過程中可以同時促進化學反應的加速進行，因此游離過程當中生成的中間產物、產物可以即時被質譜偵測到，此主題的發展仍持續成長中。在本篇論文的第一個部分，是利用高頻 (~ 1.7 MHz) 的微小型超音波霧化器為霧化樣品的裝置可在大氣壓下輔助液態樣品的氣化游離，而此方法也成功地用於小分子到大分子的質譜分析，並且利用此簡單的裝置就可以在質譜前端進行霧化游離並同時加速化學反應的進行及即時質譜線上偵測。論文中利用吉拉德T試劑及羥胺分別和類固醇進行反應為樣本反應。實驗的方法為將反應物溶液直接滴在已架在質譜前端的微小型超音波霧化器上，質譜可在一秒內可即時監測到來自生成物、中間產物及反應物的離子訊號。並且論文中也證明了，此方法可在複雜的尿液樣品中選擇偵測到來自於與類固醇反應的產物訊號，因此此反應型質譜法可以應用在未經樣品前處理的複雜樣品之分析，利用即時生成的產物訊號輔助確認複雜樣品中類固醇的存在。除此之外，基質輔助雷射脫附游離質譜之前已被成功證明可以用來快速地分析微生物樣品，利用指紋質譜圖的比對可用來達到快速辨識細菌身分的目的。在本論文第二部分，我們利用奈米探針結合漂白水、基質輔助雷射脫附游離質譜及主成分分析方法發展可以在複雜的細菌樣品中快速分辨不同屬、甚至不同亞種的細菌。即利用氧化鋁包覆氧化鐵的磁性奈米粒子為親和探針用於樣品中微量細菌的濃縮，再加入漂白水溶解細菌而利用基質輔助雷射脫附游離質譜法進行細菌溶解產物的分析，並結合主成分分析的結果可以應用於辨認如綠膿桿菌、金黃色葡萄球菌及大腸桿菌等細菌，此方法也成功用於區分不同亞種的大腸桿菌。論文中也實驗證明此方法可用於分析辨識在一毫升的尿液複雜樣品中僅含約一百顆大腸桿菌O157 : H7，即此方法之偵測極限大約為一毫升含100顆細菌。

Mass spectrometry (MS) is a powerful analytical tool that can be used to determine molecular weights and molecular structures of analytes. The progress of the ionization methods in MS is quite fast in the beginning of the 21st century because of the emerging of ambient MS (AMS). One of the advantages of AMS is that sample preparation can be minimized or eliminated. Among AMS approaches, reactive MS that can be used to monitor and to accelerate chemical reactions simultaneously during ionization process has gained considerable attentions. Furthermore, the development of reactive MS is still growing. Thus, in the first part of the thesis, an ionization method, so called ultrasonication-assisted spray ionization mass spectrometry (UASI) equipped with a miniature ultrasonic transducer (~1.7 MHz) as the ionization source was successfully used to analyze small and large molecules. Simply depositing a sample solution on the MHz-based ultrasonic transducer, which is placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Furthermore, using the UASI-MS for real-time acceleration/monitoring of chemical reactions was demonstrated. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions were readily generated and instantaneously monitored using MS within 1 s. Two reactions including Girard T reagent and hydroxylamine reacted with ketosteroids were used as the model reactions to demonstrate the feasibility of using the UASI in the applications of reactive MS. The identification of specific steroids from complex urine samples by monitoring the generation of the product ions was also demonstrated. Additionally, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been successfully used to rapidly characterize microorganisms. Pathogenic bacteria can be identified easily based on their fingerprint mass spectra. In the second part of the thesis, an approach by combining nanoprobes, use of bleach, MALDI-MS, and principal component analysis (PCA) was proposed to rapidly identify bacteria that are different in substrain/species levels from complex samples. Fe3O4@Al2O3 MNPs were used as affinity probes to rapidly enrich a sufficient number of bacterial cells from sample solutions for MS analysis by eliminating the steps of cell culture. Followed by addition of bleach, the bleach-dissolving bacterial products were analyzed by MALDI-MS. Different species of bacteria including Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli can be readily distinguished from the resultant MALDI results combined with PCA. Furthermore, different substrains of E. coli were also able to be differentiated by this approach. Only few bacterial cells such as E. coli O157:H7 (~100 cells/mL) in complex samples can be readily characterized using this proposed method.