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Development of a microfluidic Ion sensor array (Misa) to monitor gravity-DePENDENT calcium fluxes in CERATOPTERIS spores.   A. R. De Carlo1, A. ul Haque2, S.T. Wereley2, H.W. Wells3, W.T. McLamb4, S.J. Roux5, D.M. Porterfield1,6 1Dept. of Ag. & Bio. Eng., 2Dept. of Mech. Eng.,  Purdue University, West Lafayette, IN, 3Bionetics Corporation, Kennedy Space Center, FL, 4Dynamac Corporation, Kennedy Space Center, FL., 5Molecular, Cellular & Developmental Bio., Univ. of Texas, Austin, TX, 6Dept. of Horticulture & Landscape Architecture, Purdue Univ., West Lafayette, IN.

   Previous experiments that utilized self-referencing microsensors have suggested that polar calcium currents are required for gravimorphogenic development in Ceratopteris fern spores (Chatterjee et al., 2000, Planta 210: 607-610).  Further work to fully understand the physiology of the calcium signaling events in this cellular system have not progressed because of inherent limitations in the spatial/temporal resolution of current experimental sensor systems. We are now developing a   microfluidic ion sensor array (MISA) device, which includes integrated sensors, MEMS structures, and microfluidics subsystems on a silicon substrate. The MISA chip will allow us to perform real-time measurements of multidimensional calcium flux patterns around sixteen fern spores using solid-state calcium sensor arrays. The ionophore- based (ETH-5234) sensors have been fabricated and tested by obtaining calibration curves and by separate solution method interference tests. A novel coupling method, dual-electrode differential coupling (DEDC), was devised so that the differentials between two working electrodes could be amplified and digitized directly without the use of reference electrode. An 18-bit high-speed data acquisition system with customized software has been assembled to acquire data from the MISA device. The MISA system will be used in parabolic flight/microgravity based physiological experimentation, to study the role of polar calcium currents in gravity-dependent cellular development.

(Supported by NASA/Bionetics: C102-05-3 to DMP)