GRAVI: Robotized Microfluidics for Fast and Automated Immunoassays in Low Volume

GRAVI, presented here in its automated version, is a new bench-top sized immunoassay platform combining the advantages of microfluidics with those of simplified robotics. Characterized by dramatically reduced time to result (< 10 min) and significantly decreased sample/reagent consumption, the cost-efficient biosensor instrumentation allows performing multimenu analysis with minimal laboratory infrastructure. Coupled to a robotic liquid handler, the system dispenses samples and reagents from conventional plates or tubes into microchannels of a microchip (GRAVI- Chip), in which assays are processed and results readout. As in conventional 96-well microtiter plates, the microchannels have a standard spacing of 9 mm to facilitate automation. With solely gravity and capillary force-driven fluidics within the microchannels, liquids are free to flow while magnetic beads, functionalized with the antibody of choice, are trapped nearby incorporated electrodes by virtue of a magnet array. Following assay performance and electrochemical signal detection in the parallel microchannels, chips are regenerated by magnet release and rinsing of beads out from the microchannels. Applicability of the presented immunoassay platform, delivering 100 results per hour, is exemplified here with results from the validation of an immunoglobulin assay for antibody quantification in mammalian cell cultures. Adapted to run on the GRAVI platform, this competitive assay covers a dynamic range of two orders of magnitude.