Application Of Nano-Fe₃O₄ And Chinese Ink Nano-carbon In Matrix Assisted Laser Desorption Ionization Mass Spectrometry And Mass Spectrometry Imaging

Matrix assisted laser desorption/ionization mass spectrometry imaging（MALDI-MSI）,as a new molecular imaging technology,can obtain the composition,relative abundance and spatial distribution information of a large number of known or unknown compounds directly from the surface of the tissue.In the thesis,the nano-ferric oxide and Chinese ink nano-carbon were studid and appiled to analyze small molecules by MALDI-MS and MS image them in tissue section with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry（FT-ICR-MS）.（1）The nano triiron tetraoxide（nano-Fe₃O₄）was studied and applied as matrix in MALDI-MS analysis of small molecule compounds including amino acid,oligosaccharide and triglyceride.After compared with other nanoparticle matrices（nitrogen-doped carbon dots,graphite carbon nitride and titanium dioxide）and organic-inorganic binary matrices,the Fe₃O₄ nanoparticles were seelcted as matrix for the MALDI-MS analysis of pyroglutamic acid,aspartic acid,proline,phenylalanine,sucrose,raffinose,tripalmitin,and triolein.The effects of MALDI-MS experimental conditions on MS peak intensity and background noise were investigated.As result,Fe₃O₄presented the characteristics of increasing the MS peak strength and reducing background noise.Using the nano matrix to cover sample,and setting MS acquisition parameters including polarity as positive and laser power as 70%,the results showed that the nano Fe₃O₄is an ideal matrix for the detection of amino acids,oligosaccharides and triglycerides with better reproducibility and sensitivity.The MALDI-MS analysis of pyroglutamic acid,sucrose and triolein were performed using the nano Fe₃O₄matrix and there in-spot repeatability RSDs were less than 3.2%and spot-to-spot repeatability RSDs were less than 6.0%.Their linear correlation coefficients（r²）between MS peak intensity and concentrations were determined as no less than 0.997 in the concentration range of 0.05-1.0 mg/m L,which shows quantitative potential of the MALDI-MS analysis.（2）Chinese ink nanocarbon was selected as a new pre-coated matrix for MALDI-MS analysis and imaging.Chinese ink was shown that the carbon in the ink was about 20-50 nm nanomaterials by transmission electron microscope analysis.MALDI-MS experiment result also shows that the nano-carbon in Chinese ink plays the role of matrix.The mouse organs section with a thickness about 15μm were obtained after studying frozen section preparing method,which can be used for MALDI-MS with the pre-coating matrix.The effects of embedding and thickness of soybean and mouse tissue sections,matrix pre-coating method,and other experimental parameters such as laser energy and flight time were investigated.The The simulated tissue imprinted gelatin sections with the addition of glucose,sucrose and raffinose samples,and simulated pig liver homogenate tissue sections were prepared and MALDI-MS analyzed with selected conditions.For the imprinted gelatin simulation section,the MS peak intensity intra-chip repeatability RSDs<5.6%and their inter-chip repeatability RSDs<8.7%,the correlation coefficient between MS peak intensity and concentrtion were determined as no less than 0.993 in the concentration range of 2.5-25 mg/g.The MALDI-MS imaging was performed to analyze the small molecule components in soybeans.The results showed that oligosaccharides and triglycerides were almost evenly distributed in mature soybean slices,but there were differences in the radicle and cotyledons of immature soybeans.Among them,oligosaccharides were distributed more in the radicle of immature soybeans,while triglycerides were distributed more in the cotyledons.