Immunoassay with Fluidics-on-Flex™ Technology

Epocal's one-step immunoassay product platform is the first example of its Fluidics-on-Flex technology. The device features a diagnostic test card containing a flex module with an overlaying integral solid-state fluidic circuit. Fluidic elements include a lateral capillary flow micro-porous medium with a sample introduction end and a capture line (or reactor) along its length, and a pump manifold with multiple electroosmotic pumps supplying fluids at multiple fluid injection locations.

A pump supplies a specific fluid and dissolved reagents by electroosmotic flow into the lateral flow strip's capture line when a voltage is applied to the pump via the flex electrode, under control of the card reader.

Pumps are fluidically isolated from the strip before and after fluid injection. The pump manifold can include one or more of the following: a wash-fluid pump, a reporter antibody pump, a pump for multi-reporter amplification reagent (branched DNA, dendrimer, bead-based construct and the like), a substrate-injection pump (for enzyme labels) or a chemiluminescence triggering agent pump. Integral active pumping can achieve a level of performance in one-step ligand-binding methods that simply cannot be achieved using passive pumping approaches including the rudimentary fluidic format of the simple immunochromatographic strip devices of the prior art.

In a two pump configuration, a sample is introduced at the sample application end of the lateral flow strip. The sample forms a complex with a first biotinylated antibody and a second reporter (enzyme conjugate) antibody, both located as dry reagents in the sample application region. The complex, unreacted analyte and antibodies now flow along the lateral flow element through a streptavidin capture region where the analyte-antibody sandwich is captured from a known volume of fluid being collected into the lateral flow element. Next, under card-reader control, a first pump voltage is applied to a wash pump, injecting fluid into the strip at the capture line. Then, a second pump voltage is applied to a second pump, injecting an enzyme substrate fluid into the capture line.

epoc™ Immunoassay

In Epocal's first immunoassay product, the enzyme label is alkaline phosphatase and the substrate is a dioxetane which luminesces upon enzymatic dephosphorylation. Immunoassay test cards are used in conjunction with the chemiluminescence reader of the epoc™ system. The device performs quantitatively in its operating range, with sensitivity matching the levels achieved in microplate format, where less than 1000 molecules of alkaline phosphatase can be detected. This high level of performance is achieved because the lateral flow element is used as a precision volumetric sampler and concentrator into a capture line, whose micro-scale dimensions assure fast diffusion and rapid capture. There is a rigorous wash step provided by the integral pump which can remove unbound conjugate from the capture line to an exceptionally low non-specific binding level. In-situ, dark injection of the chemiluminescent substrate by a second integral pump allows differential measurement for high accuracy at low signal levels in a low cost reader format.

Immunoassay with Fluidics-on-Flex™ Technology

Epocal's one-step immunoassay product platform is the first example of its Fluidics-on-Flex technology. The device features a diagnostic test card containing a flex module with an overlaying integral solid-state fluidic circuit. Fluidic elements can include a micro-porous antibody/incubation pad, a micro-porous capture pad  (or reactor), and a pump manifold with multiple electroosmotic pumps supplying fluids at multiple fluid injection locations.