Integration and optimization of isotachophoresis on a programmable microfluidics automaton
Adam, Heritier Shebindu
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We present a programmable microfluidic array (PMA) to perform fully automated isotachophoresis (ITP) for multiple analytes simultaneously. Although conventional ITP can be time efficient for pre-concentration of a single analyte, it becomes lengthy in time to pre-concentrate multiple analytes simultaneously due to loading and unloading the sample from the device. In addition, for a successful ITP sample pre-concentration, it is critical to select appropriate leading (LE) and trailing (TE) buffers. This process can take several hours. However, with the PMA the time needed to select the buffers is significantly reduced. Using lifting gate microfluidic control valve technology, a microfluidic device consisting of a two-dimensional microvalve cellular array is fabricated with soft lithography in a format that enables facile integration with a microfluidic ITP. The lifting gate valve system was used for buffer selection, mixing and sample delivery to ITP wells. The PMA was validated by using a flow profiler to estimate volume transferred per pumping cycle and by running ITP to pre-concentrate Alexa 594 ester dye with the appropriate TE and LE buffers. To select the correct TE and LE using the PMA, three dyes Pacific blue succinimydyl ester (PB), Alexa Fluor 594 and Alexa Fluor 488 were preconcentrated with three different TE buffers: borate, HEPES and phosphate buffers were tested with different concentrations of Tris-HCl as LE. In the optimization of TE and LE 40mM borate buffer and 200mM Tris-HCl were selected as proper TE and LE buffers. The PMA-ITP system enables not only a concurrent pre-concentration of multiple analytes, but also the optimization of buffer condition without any manual involvement.