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Unformatted text preview: A robust and scalable microfluidic metering method that allows protein crystal growth by free interface diffusion Carl L. Hansen*, Emmanuel Skordalakes † , James M. Berger † , and Stephen R. Quake* ‡ *Department of Applied Physics, California Institute of Technology, MS 128-95, Pasadena, CA 91125; and † Department of Molecular and Cell Biology, University of California, 237 Hildebrand Hall, MC 3206, Berkeley, CA 94720-3206 Edited by Davis S. Eisenberg, University of California, Los Angeles, CA, and approved October 28, 2002 (received for review August 13, 2002) Producing robust and scalable fluid metering in a microfluidic device is a challenging problem. We developed a scheme for metering fluids on the picoliter scale that is scalable to highly integrated parallel architectures and is independent of the properties of the working fluid. We demonstrated the power of this method by fabricating and testingamicrofluidicchipforrapidscreeningofproteincrystallization conditions, a major hurdle in structural biology efforts. The chip has 480 active valves and performs 144 parallel reactions, each of which uses only 10 nl of protein sample. The properties of microfluidic mixing allow an efficient kinetic trajectory for crystallization, and the microfluidic device outperforms conventional techniques by detect- ing more crystallization conditions while using 2 orders of magnitude less protein sample. We demonstrate that diffraction-quality crystals may be grown and harvested from such nanoliter-volume reactions. I n the same way that miniaturization has impacted the electronics industry, microfluidics promises to spark a revolution in fields ranging from analytical chemistry to biology and medicine. In principle, microfluidic devices can increase throughput and de- crease cost by densely integrating complex assays and analytical measurements in a chip format. Driven by the early success of separation by capillary electrophoresis (1–6), other applications such as patterned surface deposition (7, 8), DNA analysis (9, 10), and cell sorting (11, 12) have been realized in microfluidic chips. The use of nanoliter reaction volumes and parallel sample process- ing represent potential advantages of microfluidic devices, making them ideally suited to total chemical analysis, ultra-high-throughput screeningapplications,andothercaseswherereagentsareprecious. However, an obstacle that thus far has hampered development of the field is the lack of a scalable, robust system to manipulate and dispense fluids with subnanoliter precision. For a fluid metering system to have universal applicability, it must be insensitive to both the specific fluid properties and the surrounding channel architecture. The need to integrate these functions into massively parallel chip architectures further requires that the method be scalable to complex devices. Previous work on microfluidic metering has resulted in the development of valveless electrokinetic and pressure-driven metering systems (13–19). Theseelectrokinetic and pressure-driven metering systems (13–19)....
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- Spring '08
- pH, Crystal, Crystallization, crystal growth, protein crystallization conditions, free interface diffusion