Hankin Joseph A, Barkley Robert M, Murphy Robert C
Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, Colorado 80045-0511, USA.
J Am Soc Mass Spectrom. 2007 Sep;18(9):1646-52. doi: 10.1016/j.jasms.2007.06.010. Epub 2007 Jun 30.
Common organic matrix-assisted laser desorption/ionization (MALDI) matrices, 2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, and alpha-cyano-4-hydroxycinnamic acid, were found to undergo sublimation without decomposition under conditions of reduced pressure and elevated temperature. This solid to vapor-phase transition was exploited to apply MALDI matrix onto tissue samples over a broad surface in a solvent-free application for mass spectrometric imaging. Sublimation of matrix produced an even layer of small crystals across the sample plate. The deposition was readily controlled with time, temperature, and pressure settings and was highly reproducible from one sample to the next. Mass spectrometric images acquired from phospholipid standards robotically spotted onto a MALDI plate yielded a more intense, even signal with fewer sodium adducts when matrix was applied by sublimation relative to samples where matrix was deposited by an electrospray technique. MALDI matrix could be readily applied to tissue sections on glass slides and stainless steel MALDI plate inserts as long as good thermal contact was made with the condenser of the sublimation device. Sections of mouse brain were coated with matrix applied by sublimation and were imaged using a Q-q-TOF mass spectrometer to yield mass spectral images of very high quality. Image quality is likely enhanced by several features of this technique including the microcrystalline morphology of the deposited matrix, increased purity of deposited matrix, and evenness of deposition. This inexpensive method was reproducible and eliminated the potential for spreading of analytes arising from solvent deposition during matrix application.
常见的有机基质辅助激光解吸/电离（MALDI）基质，如2,5-二羟基苯甲酸、3,5-二甲氧基-4-羟基肉桂酸和α-氰基-4-羟基肉桂酸，发现在减压和高温条件下会升华而不分解。这种从固态到气相的转变被用于在无溶剂的质谱成像应用中，将MALDI基质应用于大面积的组织样本上。基质的升华在样品板上产生了一层均匀的小晶体。沉积过程可以通过时间、温度和压力设置轻松控制，并且从一个样品到下一个样品具有高度的可重复性。与通过电喷雾技术沉积基质的样品相比，当通过升华应用基质时，从自动点样到MALDI板上的磷脂标准品获得的质谱图像产生了更强、更均匀的信号，且钠加合物更少。只要与升华装置的冷凝器有良好的热接触，MALDI基质就可以很容易地应用于载玻片和不锈钢MALDI板插入物上的组织切片。小鼠脑切片用升华法应用的基质进行包被，并使用Q-q-TOF质谱仪进行成像，以产生高质量的质谱图像。该技术的几个特点可能提高了图像质量，包括沉积基质的微晶形态、沉积基质纯度的提高以及沉积的均匀性。这种廉价的方法具有可重复性，并且消除了基质应用过程中因溶剂沉积而导致分析物扩散的可能性。
