Devices, systems, and methods for conducting sandwich assays using sedimentation

An apparatus for conducting a sandwich assay, the apparatus comprising:

• a substrate, wherein the substrate at least in part defines a channel;
• a fluid sample contained in the channel, wherein the fluid sample includes a plurality of beads having complexes formed thereon, individual ones of the complexes comprising a capture agent, a target analyte, and a labeling agent, wherein the fluid sample further includes free labeling agent;
• a detection region coupled to the channel and defined at least in part by the substrate;
• a media reservoir defined at least in part by the substrate and in fluid communication with the detection region, the apparatus operable to transport a density media from the media reservoir to the detection region responsive to a first centrifugal force, wherein the density media has a density within a range, an upper bound of the range being lower than a density of the plurality of beads and a lower bound of the range being higher than a density of the fluid sample;
• and
• wherein the channel is in fluid communication with the detection region such that the plurality of beads in the fluid sample are transported from the channel through the density media responsive to a second centrifugal force different than the first centrifugal force, and wherein at least a portion of the free labeling agent is restricted from transport through the density media, and wherein the plurality of beads comprise a first plurality of beads having a first property and a second plurality of beads having a second property, different than the first property such that the first plurality of beads are transported to a first distinct detection location and the second plurality of beads are transported to a second distinct detection location.

A system for conducting a sandwich assay, the system comprising:

• a microfluidic disk comprising:
• a substrate, wherein the substrate at least in part defines a channel;
• a fluid sample contained in the channel, wherein the fluid sample includes a plurality of beads having complexes formed thereon, individual ones of the complexes comprising a capture agent, a target analyte, and a labeling agent, wherein the fluid sample further includes free labeling agent;
• density media disposed in a reservoir in the microfluidic disk, wherein the density media has a density higher than a density of the fluid sample and lower than a density of the plurality of beads;
• a detection region coupled to the channel and defined at least in part by the substrate;
• and
• wherein the reservoir is coupled to the detection region such that the density media flows into the detection region responsive to a first centrifugal force and wherein the channel and detection region are coupled such that the plurality of beads in the fluid sample are transported from the channel through the density media responsive to a second centrifugal force, different from the first centrifugal force, and wherein at least a portion of the free labeling agent is restricted from transport through the density media;
• a motor coupled to the microfluidic disk, the motor configured to receive a motor control signal and spin the microfluidic disk responsive to the motor control signal;
• a detection module positioned to detect a signal from label agents included in the complexes, wherein the detection module is configured to generate an electronic detection signal based, at least in part, on the signal from the label agents;
• and
• a processing device coupled to the motor and the detection module, wherein the processing device is configured to generate the motor control signal and provide the motor control signal to the motor, and wherein the processing device is further configured to receive the electronic detection signal from the detection module.