真空紫外激光解吸/电离单细胞质谱成像装置的研制和调试

Development of Vacuum Ultraviolet Laser Desorption/Ionization Single‑Cell Mass Spectrometry Imaging Instrument

开发同时具有亚微米分辨率以及高检测灵敏度的无基质质谱成像方法,对于可视化单细胞生物样品具有重要意义。在此,提出了真空紫外激光解吸/电离飞行时间质谱成像(VUVDI-ToFMSI)方法。通过调整基频光波长至777.7、403.22和255 nm,汞蒸气池中氩气气压至1100 Pa以及温度至240℃,获得接近13μJ/pulse的高强度VUV激光能量;同时,设计的同轴光路聚焦VUV激光至亚微米水平;另外,通过进一步调整偏转电场、离子聚焦电场以及反射电场的电负性以及电压等参数,离子的飞行路径得到矫正与优化。基于这种方法,实现了单个HeLa细胞中外源性药物亚甲基蓝(m/z 284.4)、内源性代谢物离子信号m/z 152.1以及m/z 81.1的纳米级成像(~500 nm/pixel),结果表明它们分别富集在细胞质、细胞核以及核仁内,证明了该方法在绘制单细胞不同区室内外源和内源性化学物质的高分辨以及高灵敏度的成像能力。该VUVDI-ToFMSI平台将为了解更多生物样本的精细结构与功能提供更完整、更深入的化学信息。

Developing the matrix-free mass spectrometry imaging method with both sub-micron resolution and high detection sensitivity is of great significance for visualizing single-cell biological samples.Here,a vacuum ultraviolet laser desorption/ionization time-of-flight mass spectrometry imaging(VUVDI-ToFMSI)method is proposed.By adjusting the frequency wavelengths of three fundamental beams to 777.7,403.22 and 255 nm,and increasing the argon gas pressure and the temperature in the mercury vapor pool to 1100 Pa and 240℃,a high-intensity VUV laser was generated with energy close to 13μJ/pulse in the laboratory.Meanwhile,the self-designed coaxial optical path focused the VUV laser to the sub-micron level.In addition,by further optimizing the voltage of the deflection,ion focusing,and reflection electric field,the flight path of ions was corrected.Based on this method,nanoscale images(~500 nm/pixel)of exogenous drug methylene blue(m/z 284.4),endogenous metabolite ions at m/z 152.1 and m/z 81.1 were achieved in a single HeLa cell.The results showed that they were enriched in the cytoplasm,nucleus and nucleolus,respectively,demonstrating the high-resolution and high-detection-sensitivity imaging ability of this method in drawing the distributions of exogenous and endogenous chemicals in single-cell biological samples.The VUVDI-ToFMSI platform will provide more complete and in-depth chemical information for understanding the fine structure and function of more biological samples.