叶贺和里纳特·阿布扎利莫夫得到了纽约城市大学专业工作人员大会（PSC-CUNY）研究奖项目的支持。陈玉琪和凯利·维拉萨米得到了阿尔弗雷德·斯隆基金会CUNY暑期本科生研究计划的支持。

该协议遵循纽约城市大学高级科学研究中心（ASRC）机构动物护理和使用委员会（IACUC）的指导方针。
1. 收获组织
<ol><li>准备铝船。准备一个长方形铝10厘米×20厘米，折叠在中间，使10厘米双层方形。将样品信息标记在一边，将另一侧折叠起来，形成一条底部表面约 4 厘米 x 4 厘米的船。</li>
	<li>在泡沫泡沫泡沫盒中的液氮（LN2）上预制船。 注:如果船太小，样品可能会从船上掉下来，并通过直接接触LN2而变得过度冻结，这可能导致在冷冻过程中出现碎片。</li>
	<li>按照国际兽联的制度指南，通过宫颈错位对动物实施安乐死，立即解剖感兴趣的组织。<ol>
<li>尽可能缩短动物麻醉和捕捉冻结之间的间隔，以尽量减少组织采集过程中代谢物的改变，特别是死后缺血导致大脑中的实验室代谢物。 注:用磷酸盐缓冲盐水（PBS）灌注动物将增加缺血的持续时间，进一步改变阴唇代谢物的浓度，夸大人工结果。因此，不建议用 PBS 灌注或清洗组织，除非血液或体液的污染比单个项目的代谢物变质或洗涤更令人关注。</li>
	</ol>
</li>
	<li>立即将组织放入漂浮在液氮上的铝船上，关闭发泡胶盒的盖子，根据组织大小冷冻2-10分钟:产后第1天（P1）、P21、P60鼠脑分别冻结2分钟、5分钟、7分钟，P60大鼠大脑分别冻结10分钟。 注意:不要长时间冻结组织（例如P1小鼠大脑5分钟），因为过度冷冻可能导致冷冻过程中组织碎片。</li>
	<li>用钳子取出船，折叠铝箔包裹纸巾，在干冰上运输，储存在-80°C，供以后使用。如果随后立即进行分割，将干冰上的样品带到低温状态。 注:为了更好地保存代谢物，最好将样品储存在完整的组织中，并在进行 MALDI 成像之前将其分割。组织可在 -80 °C 中存储长达 24 个月。</li>
</ol>2. 组织冷冻
注意:在处理氧化钛 （ITO） 幻灯片时，请随时戴上手套。避免直接呼吸到滑梯上或戴口罩（可选），以防止人唾液污染组织部分。
<ol><li>在分割组织之前，收集与 MALDI 兼容的 ITO 涂层玻璃滑梯所需的数量。</li>
	<li>使用设置为电阻的伏特计测试幻灯片的导电性。标记电阻测量读取的侧面:这将是组织部分所坚持的侧面。务必将滑梯放在干净的纸巾上以避免污染。</li>
	<li>在设置为 -20 °C 的低温统计中预冷却幻灯片。</li>
	<li>如果从 -80 °C 中取出组织样本，则根据组织大小，让组织在低温室中均等约 45-60 分钟。如果样品从干冰中取出，则将其平衡约30分钟。</li>
	<li>用70%乙醇彻底清洁低温剂。预冷所有必要的工具，包括薄尖艺术家刷和钳子在低温室。</li>
	<li>根据组织类型设置低温室和标本头的温度:肝脏 -14 °C，肌肉 -20 °C，皮肤9-25 °C。</li>
	<li>使用冷冻组织嵌入化合物 OCT 将组织安装到夹头上，避免 OCT 从感兴趣的区域。</li>
	<li>将干净的刀片放在舞台和锁上。调整舞台位置和标本角度，实现所需的切割角度。 注意:如果要切割不同类型的组织/基因型，请务必重新定位样本，以便使用刀片的清洁部分，或在切割下一个样本之前更改为新的刀片，以防止交叉污染。</li>
	<li>继续切割，直到发现感兴趣的区域（例如，大脑中的语料库）。请务必通过用在低温统计中平衡的艺术家画笔刷掉额外的作品来保持舞台清洁。</li>
	<li>一旦所需的区域被揭示出来，削减10-12μm厚度的较小部分。如果该部分容易剥落或脱落，则将低温统计器的温度提高，保持在 -22 °C 至 -11 °C 范围内。我们发现脑组织的最佳切割温度是 -15 °C 至 - 18 °C。</li>
	<li>一旦一个好的部分被切断，坚持它到ITO幻灯片（在低温室操作）。</li>
	<li>使用艺术家画笔尖将组织的一部分转移到 ITO 幻灯片上。</li>
	<li>将手指放在滑梯下加热部分，以确保安装安全。组织部分将首先在5-10s中变成透明，然后在大约30-60s中变成不透明。</li>
	<li>小心地将幻灯片放在低温统计器中。</li>
	<li>重复其他组织样本的步骤，确保组织的每一部分均匀地放置在幻灯片上，并尽可能对齐。</li>
	<li>由于 MALDI 目标最多可容纳两个幻灯片，请将来自同一组的多个样本的部分放置在单个幻灯片或两个幻灯片上，以确保可以同时分析它们。</li>
	<li>完成后，将 ITO 滑动放入真空箱中，并转移到带干燥剂的干燥器中。真空干燥滑梯 45-60 分钟。 注意:如果实验室中没有真空干燥器，请一直将滑梯保持在 -20 °C 以下，以避免代谢物变质。</li>
	<li>幻灯片存储和运输:除非样本由 MALDI 成像核心设施准备，以便直接进行 MALDI 成像，否则将幻灯片存储在 -80 °C 或运送到干冰上的核心设施或其他 MALDI 研究实验室。</li>
	<li>为了最好地保存样品，将滑梯放入滑梯运输机中，用氮气（可选）填充，用准胶片密封，放入拉链袋中，然后放入另一个装有干燥剂的拉链袋中。给外拉链袋贴上标签。</li>
	<li>在 -80 °C（最多 6 个月）下继续储存或用足够的干冰运输。</li>
</ol>3. 矩阵准备
<ol><li>准备矩阵。 注:所有试剂必须是 HPLC 等级。<ol>
<li>以 10 毫克/mL 的浓度准备 NEDC。准备10 mL的基质溶解在溶剂70%甲醇（100毫克NEDC，7mL甲醇，3mL的H2O）。</li>
		<li>此外，还要准备额外的 10 mL 70% 甲醇:水溶液，以便在填充矩阵之前冲洗喷雾器系统。</li>
	</ol>
</li>
	<li>一旦幻灯片在步骤 2.17 中脱水，使用大胆的点银标记在组织部分外的玻璃滑梯空白处放置"X"标记，然后在银"X"顶部放置带有细点黑色标记的第二个"x"。黑色"X"与银色背景形成鲜明对比（大胆的银色"X"）稍后将作为 MALDI 仪器中后期质量光谱采集的受托标记。</li>
	<li>将滑梯加载到 MALDI 滑动金属目标中。使用塑料盖，将样品绘制到塑料盖上。留。</li>
	<li>使用平板扫描仪与 MALDI 目标一起扫描幻灯片图像。目标表面的螺丝将用作垫片，以防止扫描仪损坏或污染组织部分。在 16 位灰度和 2400 dpi 中预览和扫描选定的幻灯片区域。保存图像，以便以后在马尔迪 MSI 中使用。</li>
</ol>4. 矩阵沉积
注:有多种方法将细晶体大小的均匀矩阵层应用于 MALDI 幻灯片，包括升华、滴喷墨打印、自动矩阵喷雾器和使用艺术家 airbush9的手动喷雾。我们将使用自动矩阵喷雾器作为本协议中高可重复性示例。
<ol><li>启动:打开矩阵喷雾器单元，确保阀门位于 LOAD 位置并启动喷雾器软件。检查排气风扇是否运行良好。如果活性通风不能正常工作，请不要启动溶剂泵。</li>
	<li>在 Comms 选项卡上确认一切都在通信，然后以 0.1 mL/min 启动溶剂泵，背压为 ±500 psi（或 3.4 MPa）。</li>
	<li>通过将氮气罐设置为 30 psi 来开始压缩流向矩阵喷雾器的气流。然后，将喷雾器前部的压力调节器调整为 10 psi，并根据需要设置喷雾喷嘴温度。 注意:如果祈祷中的气压低于 5 psi，喷雾喷嘴将无法加热以保护。</li>
	<li>由于阀仍在 负载 位置，请使用注射器用 7 mL 的 70% 甲醇冲洗环路，然后用 6 mL 矩阵填充环。</li>
	<li>将组织滑入喷雾器中的支架，将两端贴上胶带以防止移动，并保留无基质边缘，以避免矩阵对 MALDI 目标的金属夹子进行污染。 注:强烈建议在进入珍贵样品幻灯片之前，先在空白显微镜幻灯片上测试矩阵喷雾。</li>
	<li>检查流量和温度是否稳定，开始喷洒。</li>
	<li>使用空白玻璃滑梯选择所需的方法进行预测试。</li>
	<li>按 开始。这将设置喷嘴温度并调整泵流量，以匹配所选方法。将阀门从 负载 切换到 喷雾 位置，然后通过单击 "继续"进行确认。</li>
	<li>允许系统运行，根据方法，每个幻灯片需要 5-20 分钟。将阀门从 喷雾切换 到 负载 位置，然后在完成后单击 "继续" 进行确认。</li>
	<li>从喷雾器中取出幻灯片，检查显微镜下矩阵涂层的图案，以确保细矩阵晶体的均匀层。</li>
	<li>矩阵沉积后，将幻灯片放入金属 MALDI 支架中立即使用。如果只有一个标本幻灯片，则添加另一个空白幻灯片以填充 MALDI 支架的两个空格。</li>
	<li>按照制造商的指示在使用后立即清理系统，以防止喷雾喷嘴堵塞。</li>
	<li>样品幻灯片涂上矩阵后，要么立即进入 MALDI 成像仪，要么使用第 2.19 步描述的相同双拉链袋制备，用干冰将其装运。 注:在紧急情况下，如 MALDI 仪器不可立即使用，将涂层滑梯存放在真空状态或 -20 °C 下长达 24 小时，尽管某些代谢物的恶化可能发生在存储期间，但尚未彻底研究。</li>
</ol>

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</ol>

作者声明没有相互竞争的经济利益。

MALDI-成像（MALDI-MSI）是一种无标签的成像技术，使研究人员能够研究各种生物分子的分布及其在组织中的修饰，这是病理学的分子基础。将 MALDI-MSI 与传统的 LC-MS 组织分析方法相结合，提供与传统 Omics 工作流相同的分子深度，但也保留了细胞网络中这些信号的空间关系。样本制备是 MALDI MSI 中最关键的一步，也是在不同实验室进行的代谢学研究的最终读出中变化的原因。在这里，我们提供了一个全面而实用的协议，以标准化使用 MALDI MSI 进行代谢分析的样本准备，希望它有利于广泛的研究团体在其当前和未来的研究中实施 MALDI MSI，从基础生物学到转化研究。
人们必须始终牢记所有预防措施，以尽量减少样品制备过程中分子剖面（丰度和空间分布）的变化，避免污染。首先，尽量减少动物安乐死和组织采集之间的时间，如原地冷冻或微波固定加热，使大脑中的酶失活，以减少对死后缺血症的责任4，5，6。其次，样品的捕捉冻结状态至关重要。冷冻不足会导致代谢物的退化和损失，而过度冷冻会导致冷冻过程中的组织碎片。冷冻时间应始终根据先前报告的研究进行测试，本文中对发育小鼠大脑的研究为啮齿动物脑组织提供了参考点。第三，切割生物组织并将其部分转移到 ITO 幻灯片中需要充分实践。请务必注意，在使用画笔从舞台上拾取部分时，应小心使用画笔。允许刷毛只接触组织部分的边缘，以降低污染和部分碎裂的风险。尽可能平整滑梯上的部分，这样可以防止在手指加热期间卷曲该部分。第四，在安装到 ITO 幻灯片上时，请确保整个部分与 ITO 幻灯片连接良好，因为组织的不同区域可能需要不同时间的手指加热。例如，脑肿瘤组织需要比正常脑组织更长的加热时间。在 MALDI-MS 扫描过程中，安装不良可能导致组织分离和碎裂。请记住，手指变暖可能使酶作用和新陈代谢导致代谢的人工变化。第五，MALDI矩阵的精细和均匀沉积在实现准确的空间信息和强 MALDI-MS 信号方面发挥了重要作用。建议在空白幻灯片上测试矩阵喷洒，并在显微镜下观察晶体图案以验证适当的覆盖范围，然后再进行珍贵标本幻灯片的涂层。最后，由于单个研究人员以不同速度执行组织采集和滑动制备，因此最好由一个人在同一组中处理样本制备，以最大限度地减少变异。
协议提供了上述详细标准程序，可根据特定实验的需要进行定制。例如，通常用于样品冷冻分割的冷冻凝胶 OCT 可以进一步用作组织夹头的安装胶（如上文所述）。先前的研究表明，OCT中的聚合物成分会导致强烈的离子抑制14。然而，在没有聚合物凝胶的额外支持的情况下，嵌入样品可能是不可避免的。为了对抗这些情况下的信号抑制，组织可能需要用70%乙醇和95%乙醇的连续清洗清洗，以去除残留的OCT来检测蛋白质或脂质，而不建议清洗用于检测小分子代谢物9。
MALDI MSI 在研究实验室和临床实践环境中越来越相关。例如，MALDI MSI最近被证明在研究蛋白造物学，以描述一个有机体15的表型功能状态，并作为微生物识别和诊断随后疾病16的代理。虽然 MALDI MSI 支持广泛的应用，但仅依靠此技术存在一些限制，尤其是在区分相似物种或代谢物以及确定特定目标方面。另一个挑战是根据 MALDI MSI 信号对代谢物浓度进行量化。人们通常认为，MALDI MSI光谱中的离子丰度与解剖组织中相应分子物种的空间分布（或相对丰度）密切相关。然而，人们应该始终记住，离子强度与相应分子物种数量之间的关系是由许多因素造成的，包括但不限于离子抑制的影响、组织结构的变化和离子分子反应17。利用内部标准的技术可以实施在MALDI-MSI18中进行绝对量化（μmol/g组织）。这两个挑战通常通过 MALDI MSI 与液相色谱串联 MS （LC-MS/MS） 技术相结合的工作流程来解决，根据该技术，MALDI-MS 允许绘制感兴趣的区域图谱，该区域随后需要微切除和 LC-MS/MS 来提供更多信息来识别代谢物19。
近年来，基于MS的成像方法被开发出来，作为以前对小分子代谢物进行成像技术的替代方式。随着 MALDI MSI 的进步和日益普及，预计 MALDI 成像将成为可视化小分子的新标准工具。在生物环境中对脂质和内源性小分子（如神经递质和代谢物）进行成像，以及为开发新药剂而成像异生物，都特别令人感兴趣。预计在不久的20年，随着马尔迪MSI的应用，这三个领域将取得迅速进展。

代谢物，代谢的中间体或最终产物，包括核苷酸、氨基酸或有机酸、脂质，是生物功能和过程的关键成分。代谢学，代谢物的研究，允许探索其生化相互作用，并理解其在基础、转化和临床研究中的作用。代谢物与生物体的表型密切相关，并提供细胞代谢过程中发生的生化活动信息。因此，除了基因组学和益生术之外，代谢学已成为了解生理和病理条件的重要工具。例如，代谢学用于阐明现有药物背后的机制及其耐受性。在药物开发中，异生物代谢有助于评估不同物种代谢物的活动或毒性，后来转化为支持个性化药物2。尽管代谢学的广泛应用，代谢物的成像可能具有挑战性，由于代谢物的化学反应性，结构异质性和广泛的浓度范围3。然而，包括高能化合物、葡萄糖、乳酸盐、糖溶胶、五氯蔗分流通路和TCA循环中间体、磷脂、神经递质、信号化合物在内的阴唇代谢物的浓度，在组织酶在组织采集过程中活跃时，如脑收获4、5、6中的死后缺血，可在几秒钟内发生变化，并在几分钟内取得进展.为确保准确的代谢数据采集，适当和仔细的样品准备是关键7，8。目前已建立的测量代谢物的平台包括NMR、酶检测和质谱（包括液体和气体色谱），最后一个平台在下面进一步讨论。
MALDI-MSI 是一种最先进的技术，它允许通过检测单个分子物种来分析复杂的样品。MALDI MSI 使能够快速和可重复地测量生物样本中的各种分子化合物的好处。质谱成像进一步允许产生基于其复合代谢物的表示组织生物学的图像，同时保留样品9中代谢物的空间分布。MALDI 能够在不使用抗体标记、结构修饰或其他专用试剂（如用于免疫染色）的情况下检测样品中的分析物，再加上它在单个实验中监测数百个分子的能力，仅包括 MS 成像在代谢分析10方面授予的一些优势， 11.除了常用的基质，如2，5-二氢苯二甲酸（DHB）和9-阿米诺阿克里丁（9-AA），最近发现了新的基质N-（1-纳芙yl）二氢二氢化二氢（NEDC），这是非常适合分析各种低分子量代谢物， 进一步改善了马尔迪MSI在代谢分析12中的应用。
尽管MALDI MSI的广泛应用，但仪器的高成本和实验程序的复杂性阻碍了其在个别研究实验室的广泛实施。因此，大多数 MALDI MSI 研究都通过共享的核心设施提供支持。样品制备，包括幻灯片制备和矩阵涂层，是 MALDI MSI 中最关键的一步。但是，幻灯片制备通常在个别研究人员的实验室进行，这为以后的 MALDI MSI 收购带来了潜在的变化。在这里，我们旨在提供一个详细的协议，为生物样本的样品准备之前，进行MALDI MSI测量，并使用发育小鼠大脑的代谢分析作为例子。

<table><tbody><tr><td>Andwin Scientific&amp;nbsp;Tissue-Tek CRYO-OCT Compound</td><td>Fisher Scientific&amp;nbsp;</td><td>14-373-65</td><td></td></tr><tr><td>Artist brush MSC #5 1/8 X 9/16 TRIM RED SABLE</td><td>Fisher Scientific&amp;nbsp;</td><td>50-111-2302</td><td></td></tr><tr><td>Autoflex speed MALDI-TOF MS system</td><td>Bruker Daltonics Inc</td><td></td><td>MALDI-TOF MS instrument</td></tr><tr><td>BD&amp;nbsp;Syringe with Luer-Lok Tips</td><td>Fisher Scientific&amp;nbsp;</td><td>14-823-16E</td><td></td></tr><tr><td>BD&amp;nbsp;Vacutainer General Use Syringe Needles</td><td>Fisher Scientific&amp;nbsp;</td><td>23-021-020</td><td></td></tr><tr><td>Bruker Daltonics&amp;nbsp;GLASS SLIDES MALDI IMAGNG</td><td>Fisher Scientific&amp;nbsp;</td><td>NC0380464</td><td></td></tr><tr><td>Drierite, with indicator, 8 mesh, ACROS Organics&amp;nbsp;</td><td>Fisher Scientific</td><td>AC219095000</td><td></td></tr><tr><td>Epson Perfection V600 Photo Scanner</td><td>Amazon</td><td>Perfection V600</td><td></td></tr><tr><td>Fisherbrand&amp;nbsp;5-Place Slide Mailer</td><td>Fisher Scientific&amp;nbsp;</td><td>HS15986</td><td></td></tr><tr><td>Fisherbrand&amp;nbsp;Digital Auto-Range Multimeter</td><td>Fisher Scientific&amp;nbsp;</td><td>01-241-1</td><td></td></tr><tr><td>FlexImaging v3.0</td><td>Bruker Daltonics Inc</td><td></td><td>Bruker MS imaging analysis software</td></tr><tr><td>HPLC Grade Methanol</td><td>Fisher Scientific&amp;nbsp;</td><td>MMX04751</td><td></td></tr><tr><td>HPLC Grade Water</td><td>Fisher Scientific&amp;nbsp;</td><td>W5-1</td><td></td></tr><tr><td>HTX M5 Sprayer</td><td>HTX Technologies, LLC</td><td></td><td>Automatic heated matrix sprayer</td></tr><tr><td>Kimberly-Clark Professional&amp;nbsp;Kimtech Science Kimwipes Delicate Task Wipers</td><td>Fisher Scientific&amp;nbsp;</td><td>06-666A</td><td></td></tr><tr><td>MSC&amp;nbsp;Ziploc Freezer Bag</td><td>Fisher Scientific&amp;nbsp;</td><td>50-111-3769</td><td></td></tr><tr><td>N -(1-Naphthyl) Ethylenediamine Dihydrochloride (NEDC)</td><td>Millipore Sigma Aldrich</td><td>222488</td><td></td></tr><tr><td>SCiLS Lab (2015b)</td><td>SCiLS Lab</td><td></td><td>Advanced MALDI MSI data analysis software</td></tr><tr><td>Thermo Scientific&amp;nbsp;CryoStar NX50 Cryostat</td><td>Fisher Thermo Scientific</td><td>95-713-0</td><td></td></tr><tr><td>Thermo Scientific&amp;nbsp;Nalgene Transparent Polycarbonate Classic Design Desiccator</td><td>Fisher Scientific&amp;nbsp;</td><td>08-642-7</td><td></td></tr></tbody></table>

sample preparation for metabolic profiling using maldi mass spectrometry imaging

代谢学是识别和量化实验样本中小分子和代谢物的研究，已成为研究发育过程中的生物活动和疾病的重要工具。代谢学方法被广泛应用于癌症、营养/饮食、糖尿病和其他涉及代谢过程的生理和病理条件的研究。本文所提倡的有助于代谢分析的有利工具是矩阵辅助激光脱光/电离子质谱成像（MALDI MSI）。它能够在不标记、结构修改或其他特殊试剂（如用于免疫染色）的情况下就地检测代谢物，使 MALDI MSI 成为推进代谢学领域相关方法的独特工具。适当的样品制备过程对于产生最佳结果至关重要，并且将成为本文的重点。

具有代表性的实验是根据 图1中显示的工作流程进行的。产后第1天、第21天、第60天（成人）发育的C57BL野型小鼠大脑按照CUNY IACUC指南采集，分别在漂浮在液氮上的铝船上冷冻2、5和7分钟。冷冻组织在标本头和腔室的 +15 °C 厚度段下冷冻。然后，组织低温被轻轻地转移到 ITO 涂层玻璃幻灯片的预冷却导电侧，以便进行 MALDI 成像。在室温下，ITO 幻灯片上的安装低温在真空中干燥 45 分钟，然后使用自动矩阵喷雾器进行矩阵沉积。矩阵 NEDC 用于检测代谢物，甲醇/水中（70/30 v/v）中 10 毫克/mL 的矩阵溶液以 0.1 mL/min 的流速沉积，喷嘴温度为 75 °C，用于 12 个周期，每个周期之间有 5 s 干燥。采用喷雾速度1300毫米/分钟，轨道间距2毫米，N2 气压10 psi，流速3L/min，喷嘴高度40毫米。
MALDI质量光谱由马尔迪飞行时间（TOF）MSI仪器以负离子模式获得。0.5-1 μL 的红磷（Pn 簇与 n = 1 - 90）甲醇乳液沉积到 ITO 幻灯片上，旁边安装的组织，并用于校准仪器在 100 -1000 m/z 质量范围内应用二次校准曲线13。激光点直径聚焦于 50μm 光刺宽度的"中等"调制光束轮廓。质量范围从 m/z 50 到 1000 的光谱以 1000 Hz 获得，用于 500 次拍摄。记录了质谱数据，并使用先进的 MALDI MSI 数据分析软件进一步分析了成像。离子图像生成时，根均值方块 （RMS） 正常化的垃圾箱宽度为 ±0.25 Da。
图2的结果显示，从每100道尔顿间隔中选择的M/z光谱MALDI MSI数据分析软件的输出图像，清楚地描绘了从小分子代谢物到高分子量脂质的光谱识别效用。每行都绘制各自的离子热图，包含产后第 1、21 和 60 天收集的三个组织中特定代谢物物种的空间和光谱信息。对于每个具有代表性的 m/z，可以使用区域分布和离子丰度分析来比较不同年龄的相应物种的相对数量。MALDI MSI 方法的一个优点是能够识别 m/z 识别的某些物种对发育里程碑或特定解剖结构的特异性。观察到一些代谢物在P1新生儿（m/z 320.1）中富集，在P60成人中富集（m/z 846.5），或在不同年龄（m/z 480.3）中均匀分布:其他分子物种特别富含灰质（m/z 117.1:524.3:765.1）、白质（m/z 673.4:846.5）或CSF/文特尔（m/z 239.0）（图2A）。代表性代谢物的空间分布，包括低氧酸（m/z 135.0）、N-乙酰-L-阿斯巴酸（m/z 174.0）、阿拉奇多尼奇 酸 （m/z 303.2）， 和几个脂质， 如利索法蒂莱他诺胺 LPE （18:1） （m/z 478.3）， LPE （20:4） （m/z 500.3）， LPE （22:6） （m/z 524.3）， 磷酸乙醇胺PE （44:: 10） （m/z 838.5），磷酸二醇PI（38:4）（m/z 885.6）也显示（图2B）。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62008/62008fig01.jpg"> 图1。马尔迪-飞行时间（TOF）质谱成像的工作流程。 捕捉冷冻组织在低温统计中低温，并安装在 ITO 幻灯片上。→ 带组织部分的幻灯片使用自动矩阵喷雾器涂上细细的矩阵层。→质谱由马尔迪-托夫MSI仪器在20-200um的光泽中收集。→ 数据进行分析，并且使用先进的 MALDI MSI 数据分析软件生成图像。缩放栏:2 毫米。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62008/62008fig01large.jpg" target="_blank">请单击此处查看此图的较大版本。</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62008/62008fig2v2.jpg"> 图2。代表输出，选定的 m/z 光谱来自质谱学，以 50 μm 的横向分辨率获得。（A） 热图描绘了从P1、P21和P60确定的三个发育里程碑中每100道尔顿/z间隔中选择的特定代谢物物种的空间分布。（B） P1、P21和P60中代表性代谢物的空间分布，包括:低氧酸、N-乙酰-L-阿斯巴酸、阿拉奇多尼酸和不同脂质物种，如利索法蒂莱诺胺（LPE）、磷酸二醇胺（PE）、磷脂二醇（PI）。缩放栏，500 μm。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62008/62008fig2v2large.jpg" target="_blank">请单击此处查看此图的较大版本。</a>

Watch this Scientific Journal Video about Sample Preparation for Metabolic Profiling using MALDI Mass Spectrometry Imaging at JoVE.com

Sample Preparation for Metabolic Profiling using MALDI Mass Spectrometry Imaging

本协议的目标是在规划使用 MALDI MSI 进行实验时，为样品制备提供详细的指导，以最大限度地提高生物样品中的代谢和分子检测。

使用 MALDI 质谱成像进行代谢分析的示例准备

Metabolomics, the study to identify and quantify small molecules and metabolites present in an experimental sample, has emerged as an important tool to ...

sample-preparation-for-metabolic-profiling-using-maldi-mass

Research

JoVE Journal

Biology

6.1K 次观看.  The City University of New York. 本协议的目标是在规划使用 MALDI MSI 进行实验时，为样品制备提供详细的指导，以最大限度地提高生物样品中的代谢和分子检测。 

视频: Sample Preparation for Metabolic Profiling using MALDI Mass Spectrometry Imaging

Preparation of Homogeneous MALDI Samples for Quantitative Applications

This protocol demonstrates a simple sample preparation to reduce spatial heterogeneity in ion signals during matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The heterogeneity of ion signals is a severe problem in MALDI, which results in poor data reproducibility and makes MALDI unsuitable for quantitative analysis. By regulating sample plate temperature during sample preparation, thermal-induced hydrodynamic flows inside droplets of sample solution are able to reduce the heterogeneity problem. A room-temperature sample preparation chamber equipped with a temperature-regulated copper base block that holds MALDI sample plates facilitates precise control of the sample drying condition. After drying of sample droplets, the temperature of sample plates is returned to room temperature and removed from the chamber for subsequent mass spectrometric analysis. The areas of samples are examined with MALDI-imaging mass spectrometry to obtain the spatial distribution of all components in the sample. In comparison with the conventional dried-droplet method that prepares samples under ambient conditions without temperature control, the samples prepared with the method demonstrated herein show significantly better spatial distribution and signal intensity. According to observations using carbohydrate and peptide samples, decreasing substrate temperature while maintaining the surroundings at ambient temperature during the drying process can effectively reduce the heterogeneity of ion signals. This method is generally applicable to various combinations of samples and matrices.

A protocol for reducing spatial heterogeneities of ion signals in MALDI mass spectrometry by regulating substrate temperature during sample drying processes is demonstrated.

定量应用同质MALDI样品的制备

This protocol demonstrates a simple sample preparation to reduce spatial heterogeneity in ion signals during matrix-assisted laser desorption/ionization ...

科研

生物化学

MALDI Sample Preparation: the Ultra Thin Layer Method

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS) 1,2. The ultra-thin layer method involves the production of a substrate layer of matrix crystals (alpha-cyano-4-hydroxycinnamic acid) on the sample plate, which serves as a seeding ground for subsequent crystallization of a matrix/analyte mixture. Advantages of the ultra-thin layer method over other sample deposition approaches (e.g. dried droplet) are that it provides (i) greater tolerance to impurities such as salts and detergents, (ii) better resolution, and (iii) higher spatial uniformity. This method is especially useful for the accurate mass determination of proteins. The protocol was initially developed and optimized for the analysis of membrane proteins and used to successfully analyze ion channels, metabolite transporters, and receptors, containing between 2 and 12 transmembrane domains 2. Since the original publication, it has also shown to be equally useful for the analysis of soluble proteins. Indeed, we have used it for a large number of proteins having a wide range of properties, including those with molecular masses as high as 380 kDa 3. It is currently our method of choice for the molecular mass analysis of all proteins. The described procedure consistently produces high-quality spectra, and it is sensitive, robust, and easy to implement.

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS).

MALDI样品制备：超薄层的方法

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption ...

生物学

Low Molecular Weight Protein Enrichment on Mesoporous Silica Thin Films for Biomarker Discovery

The identification of circulating biomarkers holds great potential for non invasive approaches in early diagnosis and prognosis, as well as for the monitoring of therapeutic efficiency.1-3 The circulating low molecular weight proteome (LMWP) composed of small proteins shed from tissues and cells or peptide fragments derived from the proteolytic degradation of larger proteins, has been associated with the pathological condition in patients and likely reflects the state of disease.4,5 Despite these potential clinical applications, the use of Mass Spectrometry (MS) to profile the LMWP from biological fluids has proven to be very challenging due to the large dynamic range of protein and peptide concentrations in serum.6 Without sample pre-treatment, some of the more highly abundant proteins obscure the detection of low-abundance species in serum/plasma. Current proteomic-based approaches, such as two-dimensional polyacrylamide gel-electrophoresis (2D-PAGE) and shotgun proteomics methods are labor-intensive, low throughput and offer limited suitability for clinical applications.7-9 Therefore, a more effective strategy is needed to isolate LMWP from blood and allow the high throughput screening of clinical samples. 
Here, we present a fast, efficient and reliable multi-fractionation system based on mesoporous silica chips to specifically target and enrich LMWP.10,11 Mesoporous silica (MPS) thin films with tunable features at the nanoscale were fabricated using the triblock copolymer template pathway. Using different polymer templates and polymer concentrations in the precursor solution, various pore size distributions, pore structures, connectivity and surface properties were determined and applied for selective recovery of low mass proteins. The selective parsing of the enriched peptides into different subclasses according to their physicochemical properties will enhance the efficiency of recovery and detection of low abundance species. In combination with mass spectrometry and statistic analysis, we demonstrated the correlation between the nanophase characteristics of the mesoporous silica thin films and the specificity and efficacy of low mass proteome harvesting. The results presented herein reveal the potential of the nanotechnology-based technology to provide a powerful alternative to conventional methods for LMWP harvesting from complex biological fluids. Because of the ability to tune the material properties, the capability for low-cost production, the simplicity and rapidity of sample collection, and the greatly reduced sample requirements for analysis, this novel nanotechnology will substantially impact the field of proteomic biomarker research and clinical proteomic assessment.

We developed a technology based on mesoporous silica thin film for the selective recovery of low molecular weight proteins and peptides from human serum. The physico-chemical properties of our mesoporous chips were finely tuned to provide substantial control in peptide enrichment and consequently profile the serum proteome for diagnostic purposes.

生物标志物发现的介孔二氧化硅薄膜的低分子量蛋白质富集

The identification of circulating biomarkers holds great potential for non invasive approaches in early diagnosis and prognosis, as well as for the ...

生物工程

Optimal Preparation of Formalin Fixed Samples for Peptide Based Matrix Assisted Laser Desorption/Ionization Mass Spectrometry Imaging Workflows

The use of matrix-assisted laser desorption/ionization, mass spectrometry imaging (MALDI MSI) has rapidly expanded, since this technique analyzes a host of biomolecules from drugs and lipids to N-glycans. Although various sample preparation techniques exist, detecting peptides from formaldehyde preserved tissues remains one of the most difficult challenges for this type of mass spectrometric analysis. For this reason, we have created and optimized a robust methodology that preserves the spatial information contained within the sample, while eliciting the greatest number of ionizable peptides. We have also aimed to achieve this in a cost effective and simple way, thereby eliminating potential bias or preparation error, which can occur when using automated instrumentation. The end result is a reproducible and inexpensive protocol.

This protocol describes a reproducible and reliable method for the sublimation-based preparation of formalin fixed tissue destined for imaging mass spectrometry.

多肽基基质辅助激光解吸/电离质谱成像中福尔马林固定样品的优化制备工作流

The use of matrix-assisted laser desorption/ionization, mass spectrometry imaging (MALDI MSI) has rapidly expanded, since this technique analyzes a host ...

Using the Open-Source MALDI TOF-MS IDBac Pipeline for Analysis of Microbial Protein and Specialized Metabolite Data

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, we developed IDBac&#8212;a low-cost and high-throughput matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bioinformatics pipeline. IDBac software is designed for non-experts, is freely available, and capable of analyzing a few to thousands of bacterial colonies. Here, we present procedures for the preparation of bacterial colonies for MALDI-TOF MS analysis, MS instrument operation, and data processing and visualization in IDBac. In particular, we instruct users how to cluster bacteria into dendrograms based on protein MS fingerprints and interactively create Metabolite Association Networks (MANs) from specialized metabolite data.

IDBac is an open-source mass spectrometry-based bioinformatics pipeline that integrates data from both intact protein and specialized metabolite spectra, collected on cell material scraped from bacterial colonies. The pipeline allows researchers to rapidly organize hundreds to thousands of bacterial colonies into putative taxonomic groups, and further differentiate them based on specialized metabolite production.

使用开源 MALDI TOF-MS IDBac 管道分析微生物蛋白和专用代谢物数据

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, ...

Investigation of Xenobiotics Metabolism In Salix alba Leaves via Mass Spectrometry Imaging

The method presented uses mass spectrometry imaging (MSI) to establish the metabolic profile of S. alba leaves when exposed to xenobiotics. Using a non-targeted approach, plant metabolites and xenobiotics of interest are identified and localized in plant tissues to uncover&#160;specific distribution patterns. Then, in silico prediction of potential metabolites (i.e., catabolites and conjugates) from the identified xenobiotics is performed. When a xenobiotic metabolite is located in the tissue, the type of enzyme involved in its alteration by the plant is recorded. These results were used to describe different types of biological reactions occurring in S. alba leaves in response to xenobiotic accumulation in the leaves. The metabolites were predicted in two generations, allowing the documentation of successive biological reactions to transform xenobiotics in the leaf tissues.

Investigation of Xenobiotics Metabolism In Salix alba Leaves via Mass Spectrometry Imaging

This method uses mass spectrometry imaging (MSI) to understand metabolic processes in S. alba leaves when exposed to xenobiotics. The method allows the spatial localization of compounds of interest and their predicted metabolites within specific, intact tissues.

通过质谱成像对 萨利克斯阿尔巴 叶中异种生物代谢的调查

The method presented uses mass spectrometry imaging (MSI) to establish the metabolic profile of S. alba leaves when exposed to xenobiotics. Using a ...

环境科学

Sample Preparation Strategies for Mass Spectrometry Imaging of 3D Cell Culture Models

Three dimensional cell cultures are attractive models for biological research. They combine the flexibility and cost-effectiveness of cell culture with some of the spatial and molecular complexity of tissue. For example, many cell lines form 3D structures given appropriate in vitro conditions. Colon cancer cell lines form 3D cell culture spheroids, in vitro mimics of avascular tumor nodules. While immunohistochemistry and other classical imaging methods are popular for monitoring the distribution of specific analytes, mass spectrometric imaging examines the distribution of classes of molecules in an unbiased fashion. While MALDI mass spectrometric imaging was originally developed to interrogate samples obtained from humans or animal models, this report describes the analysis of in vitro three dimensional cell cultures, including improvements in sample preparation strategies. Herein is described methods for growth, harvesting, sectioning, washing, and analysis of 3D cell cultures via matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) imaging. Using colon carcinoma 3D cell cultures as a model system, this protocol demonstrates the ability to monitor analytes in an unbiased fashion across the 3D cell culture system with MALDI-MSI.

Immortalized cancer cell lines can be grown as 3D cell cultures, a valuable model for biological research. This protocol describes mass spectrometry imaging of 3D cell cultures, including improvements in the sample preparation platform. The goal of this protocol is to instruct users to prepare 3D cell cultures for mass spectrometry imaging analysis.

样品制备策略的3D细胞培养模型质谱成像

Three dimensional cell cultures are attractive models for biological research. They combine the flexibility and cost-effectiveness of cell culture with ...

Dithranol as a Matrix for Matrix Assisted Laser Desorption/Ionization Imaging on a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

Mass spectrometry imaging (MSI) determines the spatial localization and distribution patterns of compounds on the surface of a tissue section, mainly using MALDI (matrix&#160;assisted laser desorption/ionization)-based analytical techniques. New matrices for small-molecule MSI, which can improve the analysis of low-molecular weight (MW) compounds, are needed. These matrices should provide increased analyte signals while decreasing MALDI background signals. In addition, the use of ultrahigh-resolution instruments, such as Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, has&#160;the ability to resolve analyte signals from matrix signals, and this can partially overcome many problems associated with the background originating from the MALDI matrix. The reduction in the intensities of the metastable matrix clusters by FTICR MS can also help to overcome some of the interferences associated with matrix peaks on other instruments. High-resolution instruments such as the FTICR mass spectrometers are advantageous as they can produce distribution patterns of many compounds simultaneously while still providing confidence in chemical identifications. Dithranol (DT; 1,8-dihydroxy-9,10-dihydroanthracen-9-one) has previously been reported as a MALDI matrix for tissue imaging. In this work, a protocol for the use of DT for MALDI imaging of endogenous lipids from the surfaces of mammalian tissue sections, by positive-ion MALDI-MS, on an ultrahigh-resolution hybrid quadrupole FTICR instrument has been provided.

Dithranol (DT; 1,8-dihydroxy-9,10-dihydroanthracen-9-one) has previously been reported as a MALDI matrix for tissue imaging of small molecules; protocols for the use of DT for the MALDI imaging of endogenous lipids on the surface of tissue sections&#160;by positive-ion MALDI-MS on an ultrahigh-resolution quadrupole-FTICR instrument are provided here.

地蒽酚作为傅立叶的基质辅助激光解吸/离子化成像矩阵变换离子回旋共振质谱仪

Mass spectrometry imaging (MSI) determines the spatial localization and distribution patterns of compounds on the surface of a tissue section, mainly ...

MALDI-Mass Spectrometric Imaging for the Investigation of Metabolites in Medicago truncatula Root Nodules

Most techniques used to study small molecules, such as pharmaceutical drugs or endogenous metabolites, employ tissue extracts which require the homogenization of the tissue of interest that could potentially cause changes in the metabolic pathways being studied1. Mass spectrometric imaging (MSI) is a powerful analytical tool that can provide spatial information of analytes within intact slices of biological tissue samples1-5. This technique has been used extensively to study various types of compounds including proteins, peptides, lipids, and small molecules such as endogenous metabolites. With matrix-assisted laser desorption/ionization (MALDI)-MSI, spatial distributions of multiple metabolites can be simultaneously detected. Herein, a method developed specifically for conducting untargeted metabolomics MSI experiments on legume roots and root nodules is presented which could reveal insights into the biological processes taking place. The method presented here shows a typical MSI workflow, from sample preparation to image acquisition, and focuses on the matrix application step, demonstrating several matrix application techniques that are useful for detecting small molecules. Once the MS images are generated, the analysis and identification of metabolites of interest is discussed and demonstrated. The standard workflow presented here can be easily modified for different tissue types, molecular species, and instrumentation.

MALDI-Mass Spectrometric Imaging for the Investigation of Metabolites in Medicago truncatula Root Nodules

Mass spectrometric imaging (MSI) is a powerful tool that can be used to discover and identify various chemical species in intact tissues, preserving the compounds in their native environments, which can provide new insights into biological processes. Herein a MSI method developed for the analysis of small molecules is described.&#160;

MALDI-质谱成像代谢物的研究<em&gt;苜蓿</em&gt;根瘤

Most techniques used to study small molecules, such as pharmaceutical drugs or endogenous metabolites, employ tissue extracts which require the ...

<meta charset="utf8"></head><body> 脑类器官中代谢物的高级 MALDI-MSI 映射

Molecular Imaging of Human Brain Organoids Using Mass Spectrometry 

Brain organoid models serve as a powerful tool for studying human brain development and function. Mass spectrometry imaging (MSI), a cutting-edge technology, allows us to map the spatial distribution of diverse molecules such as lipids, sugars, amino acids, drugs, and their metabolites within these organoids, all without the need for specific molecular probes. High-quality MSI data hinge on meticulous sample preparation. Fixatives play a pivotal role, but conventional options such as glutaraldehyde, paraformaldehyde, and cryopreserving such as sucrose may inadvertently impact tissue metabolites. Optimal fixation entails flash freezing in liquid nitrogen. However, for small organoids, a more suitable approach involves transitioning the organoids directly from the incubator into a warmed embedding solution, followed by freezing in dry ice-cooled ethanol. Another critical step is the embedding prior to cryosectioning, which also requires materials compatible with MSI, as traditional options can interfere with matrix deposition and ionization. Here, an optimized protocol for high resolution-MALDI-MSI of human brain organoids is presented, encompassing sample preparation, sectioning, and imaging using mass spectrometry. This method showcases the molecular distribution of small metabolites, such as amino acids, with high mass accuracy and sensitivity. As such, coupled with complementary studies of brain organoids, it can assist in illuminating complex processes governing early brain development, metabolic cell fate trajectories, and distinctive metabolite signatures. Furthermore, it provides insights into the precise locations of molecules within the organoid, enriching our understanding of the spatial organization of 3D brain organoid models. As the field continues to advance, a growing number of studies leveraging MSI to delve into brain organoids and complex biological systems is anticipated, thereby deepening the understanding of the metabolic aspects of human brain function and development.

<meta charset="utf8"></head><body>使用质谱法对人脑类器官进行分子成像

An advanced method was developed for mass spectrometry imaging (MSI) of brain organoids that allows mapping metabolite distributions within these models. This technology offers insights into brain metabolic pathways and metabolite signatures during early development and in disease, promising a deeper understanding of the human brain function.

使用 MALDI 质谱成像进行代谢分析的示例准备

摘要

探索更多视频

定量应用同质MALDI样品的制备

MALDI样品制备：超薄层的方法

生物标志物发现的介孔二氧化硅薄膜的低分子量蛋白质富集

多肽基基质辅助激光解吸/电离质谱成像中福尔马林固定样品的优化制备工作流

使用开源 MALDI TOF-MS IDBac 管道分析微生物蛋白和专用代谢物数据

通过质谱成像对萨利克斯阿尔巴叶中异种生物代谢的调查

样品制备策略的3D细胞培养模型质谱成像

地蒽酚作为傅立叶的基质辅助激光解吸/离子化成像矩阵变换离子回旋共振质谱仪

MALDI-质谱成像代谢物的研究

使用质谱法对人脑类器官进行分子成像

使用 MALDI 质谱成像进行代谢分析的示例准备

摘要

探索更多视频

定量应用同质MALDI样品的制备

MALDI样品制备：超薄层的方法

生物标志物发现的介孔二氧化硅薄膜的低分子量蛋白质富集

多肽基基质辅助激光解吸/电离质谱成像中福尔马林固定样品的优化制备工作流

使用开源 MALDI TOF-MS IDBac 管道分析微生物蛋白和专用代谢物数据

通过质谱成像对 萨利克斯阿尔巴 叶中异种生物代谢的调查

样品制备策略的3D细胞培养模型质谱成像

地蒽酚作为傅立叶的基质辅助激光解吸/离子化成像矩阵变换离子回旋共振质谱仪

MALDI-质谱成像代谢物的研究

使用质谱法对人脑类器官进行分子成像

通过质谱成像对萨利克斯阿尔巴叶中异种生物代谢的调查