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Magnetically Driven Mixing within a Microarray Geometry Using Functionalized Magnetic Nanoparticles

Sandip Agarwal and Paul E. Laibinis. Rice University, 6100 S. Main Street, Houston, TX 77005

Microarrays have found widespread use for probing genomic and proteomic functions. These systems consist of a purposefully spotted microscopic slide of different biological samples (the microarray), a sub-milliliter solution volume containing target molecules of interest, and a coverslip to contain and spread the solution over the microarray surface. Incubation or hybridization times for the target solution with the microarray can be as long as a day to allow binding of target molecules to probes on the array surface. These times are limited by the reliance on diffusional processes for transport within this thin-film geometry. We have pursued approaches for providing solution movement and mixing within this confined geometry by using functionalized magnetite nanoparticles that are included within the target solution and a sweeping magnetic field that together provide mixing within the microarray chamber. The effects of particle size, concentration, magnetic path, and movement velocity have each been investigated, resulting in an optimization of accelerated mixing within the chamber. The particles have been prepared to incorporate surface functional groups that make them non-interacting with functionalities present on the microarray surface or toward target molecules in solution, thereby providing a component that is readily removed from the system prior to reading of a microarray. A goal of the work is to reduce the timescale for performing a microarray from roughly a day presently to a few hours. Present experiments suggest possibilities for both accelerating timescales as well as for improving the quality of data sets by use of the developed mixing strategy.