Matrix‐assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) allows for highly multiplexed, untargeted detection of many hundreds of analytes from tissue. Recently, laser postionization (MALDI‐2) has been developed for increased ion yield and sensitivity for lipid IMS. However, the dependence of MALDI‐2 performance on the various lipid classes is largely unknown. To understand the effect of the applied matrix on MALDI‐2 analysis of lipids, samples including an equimolar lipid standard mixture, various tissue homogenates, and intact rat kidney tissue sections were analyzed using the following matrices: α‐cyano‐4‐hydroxycinnamic acid, 2′,5′‐dihydroxyacetophenone, 2′,5′‐dihydroxybenzoic acid (DHB), and norharmane (NOR). Lipid signal enhancement of protonated species using MALDI‐2 technology varied based on the matrix used. Although signal improvements were observed for all matrices, the most dramatic effects using MALDI‐2 were observed using NOR and DHB. For lipid standards analyzed by MALDI‐2, NOR provided the broadest coverage, enabling the detection of all 13 protonated standards, including nonpolar lipids, whereas DHB gave less coverage but gave the highest signal increase for those lipids recorded. With respect to tissue homogenates and rat kidney tissue, mass spectra were compared and showed that the number and intensity of neutral lipids tentatively identified with MALDI‐2 using NOR increased significantly (e.g., fivefold intensity increase for triacylglycerol). In the cases of DHB with MALDI‐2, the number of protonated lipids identified from tissue homogenates doubled with 152 on average compared with 76 with MALDI alone. High spatial resolution imaging (~20 μm) of rat kidney tissue showed similar results using DHB with 125 lipids tentatively identified from MALDI‐2 spectra versus just 72 using standard MALDI. From the four matrices tested, NOR provided the greatest increase in sensitivity for neutral lipids (triacylglycerol, diacylglycerol, monoacylglycerol, and cholesterol ester), and DHB provided the highest overall number of lipids detected using MALDI‐2 technology.

中文翻译：

---

MALDI 基质对使用 MALDI-2 定位质谱法进行生物组织脂质分析的影响


基质辅助激光解吸/电离成像质谱 (MALDI IMS) 可以对组织中的数百种分析物进行高度多重、非靶向检测。最近，开发了激光定位 (MALDI-2)，以提高脂质 IMS 的离子产量和灵敏度。然而，MALDI-2 性能对各种脂质类别的依赖性在很大程度上尚不清楚。为了了解所应用的基质对脂质的 MALDI-2 分析的影响，使用以下基质分析了包括等摩尔脂质标准混合物、各种组织匀浆和完整大鼠肾组织切片的样品：α-氰基-4-羟基肉桂酸、α-氰基-4-羟基肉桂酸、 2',5'-二羟基苯乙酮、2',5'-二羟基苯甲酸 (DHB) 和去甲哈尔烷 (NOR)。使用 MALDI-2 技术增强质子化物质的脂质信号根据所使用的基质而有所不同。尽管所有基质均观察到信号改善，但使用 NOR 和 DHB 观察到使用 MALDI-2 的最显着效果。对于 MALDI-2 分析的脂质标准品，NOR 提供了最广泛的覆盖范围，能够检测所有 13 种质子化标准品，包括非极性脂质，而 DHB 的覆盖范围较小，但对记录的脂质提供了最高的信号增强。对于组织匀浆和大鼠肾组织，比较了质谱，结果表明使用 NOR 通过 MALDI-2 初步鉴定的中性脂质的数量和强度显着增加（例如，三酰甘油的强度增加了五倍）。在使用 MALDI-2 进行 DHB 的情况下，从组织匀浆中鉴定出的质子化脂质数量平均增加了一倍，达到 152 个，而仅使用 MALDI 时则为 76 个。 使用 DHB 对大鼠肾组织进行高空间分辨率成像（~20 μm）显示相似的结果，其中从 MALDI-2 光谱中初步鉴定出 125 种脂质，而使用标准 MALDI 只能鉴定出 72 种脂质。在测试的四种基质中，NOR 对中性脂质（三酰甘油、二酰甘油、单酰甘油和胆固醇酯）的敏感性增加最大，而 DHB 则使用 MALDI-2 技术检测到的脂质总数最高。