Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is a powerful label-free technique for mapping the spatial distribution of biomolecules directly from tissue. However, like most other MSI techniques, it suffers from low ionization yields and ion suppression effects for biomolecules that might be of interest for a specific application at hand. Recently, a form of laser post-ionization was introduced (coined MALDI-2) that critically boosts the ion yield for many glyco- and phospholipids by several orders of magnitude and makes the detection of further biomolecular species possible. While the MALDI-2 technique is being increasingly applied by the MSI community, it is still only implemented in fine vacuum ion sources in a pressure range of about 1-10 mbar. Here, we show the first implementation of the technique to a custom-built atmospheric pressure ion source coupled to an Orbitrap Elite system. We present results from parameter optimization of MALDI-2 at atmospheric pressure, compare our findings to previously published fine vacuum data and show first imaging results from mouse cerebellum with 20 µm pixel size. Our findings broaden the feasibility of the technique to overall more flexible atmospheric pressure ion sources.

中文翻译：

---

大气压下的MALDI-2-参数优化和首次成像实验。

基质辅助激光解吸/电离质谱成像（MALDI-MSI）是一种功能强大的无标记技术，可直接绘制来自组织的生物分子的空间分布。但是，像大多数其他MSI技术一样，它还面临着低电离产率和对生物分子的离子抑制效应的困扰，这对于手头的特定应用可能是有意义的。最近，引入了一种激光后电离的形式（硬币化的MALDI-2），该技术可以将许多糖和磷脂的离子产率显着提高几个数量级，并使得进一步检测生物分子成为可能。尽管MALDI-2技术已被MSI社区越来越多地应用，但它仍仅在压力范围约为1-10 mbar的精细真空离子源中实施。这里，我们向与Orbitrap Elite系统耦合的定制大气压离子源展示了该技术的首次实现。我们介绍了在大气压力下MALDI-2参数优化的结果，将我们的发现与先前发表的精细真空数据进行了比较，并显示了来自小鼠小脑的20微米像素大小的首次成像结果。我们的发现将这项技术的可行性扩大到整体上更灵活的大气压离子源。