Biomedical Engineering Interdepartmental PhD Program, University of California, Los Angeles, CA 90095-1600, USA.
Lab Chip. 2012 Jul 21;12(14):2552-9. doi: 10.1039/c2lc21135a. Epub 2012 May 9.
A droplet (digital) microfluidic device has been developed that enables complete protein sample preparation for MALDI-MS analysis. Protein solution dispensing, disulfide bond reduction and alkylation, tryptic digestion, sample crystallization, and mass spectrometric analysis are all performed on a single device without the need for any ex situ sample purification. Fluorinated solvents are used as an alternative to surfactants to facilitate droplet movement and limit protein adsorption onto the device surface. The fluorinated solvent is removed by evaporation and so does not interfere with the MALDI-MS analysis. Adding a small amount of perfluorooctanoic acid to the MALDI matrix solution improves the yield, quality and consistency of the protein-matrix co-crystals, reducing the need for extensive 'sweet spot' searching and improving the spectral signal-to-noise ratio. These innovations are demonstrated in the complete processing and MALDI-MS analysis of lysozyme and cytochrome c. Because all of the sample processing steps and analysis can be performed on a single digital microfluidic device without the need for ex situ sample handling, higher throughput can be obtained in proteomics applications. More generally, the results presented here suggest that fluorinated liquids could also be used to minimize protein adsorption and improve crystallization in other types of lab-on-a-chip devices and applications.
已经开发出一种液滴（数字）微流控装置，可实现 MALDI-MS 分析用完整蛋白质样品制备。蛋白质溶液分配、二硫键还原和烷基化、胰蛋白酶消化、样品结晶和质谱分析都在单个装置上进行，而无需任何原位样品纯化。使用氟化溶剂代替表面活性剂来促进液滴运动并限制蛋白质吸附到装置表面。氟化溶剂通过蒸发去除，因此不会干扰 MALDI-MS 分析。向 MALDI 基质溶液中添加少量全氟辛酸可提高蛋白质-基质共晶的产率、质量和一致性，减少对广泛的“最佳点”搜索的需求，并提高光谱信号-噪声比。这些创新在溶菌酶和细胞色素 c 的完整处理和 MALDI-MS 分析中得到了证明。由于所有的样品处理步骤和分析都可以在单个数字微流控装置上进行，而无需进行原位样品处理，因此可以在蛋白质组学应用中获得更高的通量。更一般地说，这里呈现的结果表明，氟化液体也可以用于最小化蛋白质吸附并改善其他类型的芯片实验室设备和应用中的结晶。
