A high-throughput, low-volume microfluidic device has been designed to decouple the physical processes of protein crystal nucleation and growth. This device, called the Phase Chip, is constructed out of poly (dimethylsiloxane) (PDMS) elastomer. One of the Phase Chip's innovations is to exploit surface tension forces to guide each drop to a storage chamber. We demonstrate that nanoliter water-in-oil drops of protein solutions can be rapidly stored in individual wells, thereby allowing the screening of 1000 conditions while consuming a total of only 10 mu g of protein on a 20 cm 2 chip. Another significant advance over current microfluidic devices is that each well is in contact with a reservoir via a dialysis membrane through which only water and other low-molecular-weight organic solvents can pass, but not salt, polymer, or protein.-This enables the concentration of all solutes in a solution to be reversibly, rapidly, and precisely varied in contrast to current methods, such as the free interface diffusion or sitting drop methods, which are irreversible. The Phase Chip operates by first optimizing conditions for nucleation by using dialysis to supersaturate the protein solution, which leads to nucleation of many small crystals. Next, conditions are optimized for crystal growth by using dialysis to reduce the protein and precipitant concentrations, which leads small crystals to dissolve while simultaneously causing only the largest ones to grow, ultimately resulting in the transformation of many small, unusable crystals into a few large ones.
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机译：高通量，小体积的微流控设备已被设计用来分离蛋白质晶体成核和生长的物理过程。这种称为相芯片的设备由聚二甲基硅氧烷（PDMS）弹性体制成。 Phase Chip的一项创新是利用表面张力将每个液滴引导至存储腔。我们证明蛋白质溶液的纳升油包水型滴剂可以快速存储在各个孔中，从而允许筛选1000种条件，而在20 cm 2的芯片上总共仅消耗10μg蛋白质。当前微流控设备的另一个重大进步是，每个孔都通过透析膜与储层接触，只有水和其他低分子量有机溶剂可以通过透析膜，而盐，聚合物或蛋白质则不能通过。与目前不可逆的方法（例如自由界面扩散法或坐滴法）相比，溶液中所有溶质的浓度可逆，快速和精确地变化。相位芯片首先通过使用透析使蛋白质溶液过饱和来优化成核条件，从而导致许多小晶体成核。接下来，通过透析以减少蛋白质和沉淀剂的浓度来优化晶体生长的条件，这导致小晶体溶解，而同时仅导致最大的晶体生长，最终导致许多小的，无法使用的晶体转变为少数大的晶体那些。
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