Dmf method and system for concentrating analyte from large volumes into smaller volumes using magnetic microparticles

A system for sequestering and concentrating an analyte from a volume of liquid sample to a droplet of reagent with a smaller volume, comprising:

• a) a digital microfluidic device having an array of driving electrodes and a passive pumping mechanism for pumping liquid from a liquid reservoir to an exit;
• b) a magnet positioned to apply a focused magnetic field adjacent to one or more preselected driving electrodes to form a holding location when in operation;
• c) computer controller programmed for applying preselected patterns of voltages to said array of driving electrodes;
• d) means for exposing magnetic microparticles coated with analyte specific receptors to a volume of liquid sample containing the analytes located remote from said digital microfluidic device and placing the volume of liquid containing the magnetic microparticles into the reservoir;
• e) the computer controller being programmed for forming a virtual fluid flow channel by activing a preselected pattern of driving electrodes with a preselected pattern of voltages across the digital microfluidic device from the reservoir to an exit location from which liquid is to be removed from the digital microfluidic device while at the same time applying a magnetic field at a preselected holding location along the virtual fluid flow channel, wherein upon activating the preselected pattern of driving electrodes, liquid from the volume of liquid in the reservoir traverses a distance from the reservoir to the exit location and the magnetic microparticles with the analyte bound to the analyte specific receptors moving from the reservoir, upon reaching the holding location, are substantially held at the holding location by the magnetic field, and the remaining liquid remains flowing to the exit location by means of a pump mechanism to be removed from the digital microfluidic device;
• f) means for dispensing a droplet of a reagent over the magnetic microparticles held at the holding location by the magnetic field, said droplet of reagent having a smaller volume compared to the volume of liquid, removing the magnetic field at the holding location and further processing the droplet of reagent containing the magnetic microparticles;
• and
• g) wherein the droplet of reagent containing the magnetic microparticles having the analytes bound thereto contains a higher concentration of the analyte as compared to a concentration of the analyte in the volume of liquid.