Preparation Of Functional Nanomaterials And Application In MALDI-TOF MS Analysis

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an effective instrumental tool for analysis of nonvolatile large molecules. Its superior advantages including easy sample preparation, soft ionization, low fragmentation, high sensitivity, good salt tolerance, as well as fast and high-throughput data acquisition all make it an increasingly popular technique for sample detection and identification. However, there are still challenges in broadening its application to small molecules, as well as comreshensively investigating phosphoproteome due to the low abundance of phosphoproteins and the stoicheiometry of phosphorylation sites.In this thesis, based on the platform of nanotechnology, we synthesized a series of functional nanomaterials with various composition and morphology, and applied them as MALDI matrix or in phosphopeptide enrichment for further MS analysis. Besides, with the aid of the concept of microchip, fast analysis for minute sample was eventually realized. The detailed contents were described as follows:1. N-doped graphene as an alternative carbon-based matrix for highly efficient detection of small molecules by negative ion MALDI-TOF MS.In this study, gas-phase N-doped graphene (gNG) was synthesized by a modified thermal annealing method and then for the first time applied as the matrix in negative-ion MALDI-TOF MS analysis. Based on gNG assisted D/I process, successful applications were carried out on a wide range of low melecular weight analytes with good salt tolerance and high ionization efficiency. The extraordinary LDI efficiency of gNG over traditional CHCA and undoped graphene materials was investigated to be originate from its two key properties. This work created a new application branch for nitrogen-doped graphene and provided an alternative solution for small molecule analysis.2. Synthesis of Fe3O4-Graphene-TiO2 Ternary Composite Networks for Enhanced Capture of PhosphopeptidesFe3O4-graphene-TiO2 ternary composite networks were first preprared by electrostatic assembly of Fe3O4 nanoparticles and in situ synthesis of TiO2 nanoparticles on graphene nanosheets. The ternary composites exhibited high selectivity and capacity in the capture of phosphopeptides, due to the enhanced contact to phosphopeptides given by graphene scaffold. Besides, ascribed to magnetic separability from Fe3O4 nanoparticles, FeaO4-graphene-TiO2 could be conveniently separated from the sample solution, fascinating the pretreatment process. We further applied this material in a complex sample, human serum for enrichment of endogenous phosphopeptides, demonstrating its high selectivity and good anti-interference.3. Tailoring of a TiO2 nanotube array-integrated portable microdevice for efficient on-chip enrichment of phosphopeptidesBy means of electrochemical anodic corrosion, TiO2 nanotube arrays were successfully prepared in a patterned domain on glass slide. Employing TiO2 nanotube arrays domain as separation bed and patterned PDMS as cover, we constructed TiO2 nanotube arrays/PDMS microdevice, and applied it in on-chip enrichment of phosphopeptides. Without any instrument, gravity driven injection was employed here for sample processing, realizing fast analysis for minute sample. This is the first time for TiO2 nanotube arrays to be integrated into a microdevice for phosphopeptide separation and enrichment.