| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 97 === This thesis is divided into two parts. In the first part, we have employed two sets of differently sized (average diameters: 3.5 and 14 nm) gold nanoparticles (Au NPs) as selective probes and matrices for the determination of aminothiols in biological samples using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Because of their higher ionization efficiency, the 3.5-nm-diameter Au NPs exhibited greater desorption/ionization efficiency toward the aminothiols than did the larger Au NPs; centrifugation of these small Au NPs was, however, difficult. To solve this problem, we investigated the use of mixtures of the 3.5- and 14-nm Au NPs; in this case, the analyte-induced Au NP aggregates were readily centrifuged, providing greater concentration efficiency. When using 38 and 150 pM solutions of the 3.5- and 14-nm Au NPs, respectively, as the probe and matrix, SALDI-MS provided limits of detection (signal-to-noise ratio = 3) of 2, 20, and 44 nM for 1.0-mL solutions of glutathione (GSH), cysteine (Cys), and homocysteine, respectively. We validated the practicality of this approach—with its advantages of sensitivity, reproducibility, rapidity, and simplicity—through the analysis of GSH in MCF-7 cell lysates and Cys in plasma.
In the second part, we have synthesized and investigated the uses of nanomaterials, including Au NPs, Pt nanosponges (NSP), Fe3O4 NPs, TiO2 NPs, Se NPs, and CdTe quantum dots (QDs), as SALDI-MS matrixes for the analysis of small molecules, peptides and proteins. Although those nanomaterials served as useful inorganic matrixes in the SALDI-MS measurements, SALDI-MS performance with respect to sensitivity, reproducibility, and mass range is highly dependent on the nature and concentrations of NPs. Thus, our aim of this study is to evaluate different NP matrixes for analyzing biomolecules in those optimum conditions. We found that for small solutes (e.g. glutathione), Au NPs provided the lowest (140 fmol) limit of detection (LOD) at signal-to-noise ration 3. And the upper detectable mass range is approximately 25 kDa by using Pt NSPs and Fe3O4 NPs as the SALDI-MS matrix. For efficient desorption and ionization, nanomaterials need to have a strong absorption of laser energy and an efficient proton energy transfer to the analytes, while their interactions with analytes can not be too strong. With respect to sensitivity, the nanomaterials must be stable under laser irradiation; minimum formation of clusters from the nanomaterials such as Au clusters. Although Fe3+ and Cd2+ have strong interactions with proteins, leading to improved ionization efficiency (sensitivity), they cause peak broadening (loss in mass resolution).
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