Method: Time-Resolved Fluorescent Immunoassay; Fluorescent Immunoassay Lateral Flow Cartridge; The Time-Resolved Technology Of Humafia - Human HumaFIA User Manual

2 SYSTEM DESCRIPTION 15

2.4 Method: time-resolved fluorescent immunoassay

2.4.1 Fluorescent immunoassay lateral flow cartridge

Lateral flow assays with dry reagents are simple to use, but very specific due to their antibody detection
method.
Principle: The test uses a sandwich detection method to determine an analyte like CRP in a specimen. If the
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analyte is present in the sample, the Eu labelled antibody will capture analytes flowing downstream in the
nitrocellulose membrane. The immunocomplex is then captured in the test area by a fixed antibody, forming
antibody-antigen-antibody complexes. The more antigen/analyte in the sample, the more immunocomplexes
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are captured in the test area. This leads to a stronger intensity of the Eu fluorescence signal, which is
processed by the instrument displaying the analyte concentration of the sample.
Figure 2-8 Reaction principle
Stable dry reagent cartridges are ready to use (4-30 °C) for easy storage and transportation. Whole blood,
serum and plasma are supported sample types. Refer to the corresponding IFU for each parameter.

2.4.2 The time-resolved technology of HumaFIA

The highly sensitive time-resolved fluorescent immunoassay (TR-FIA) technology is based on fluorescent
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europium Eu chelates, with large Stokes shifts, narrow emission bands and long fluorescence lifetimes.
Conventional fluorescence dyes emit only during a short period of time after the excitation pulse. However,
in that first time span auto-fluorescence emission occurs, too, which contributes to the background signal of
conventional tests.
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Time-resolved technology, based on Eu with long fluorescence lifetimes, allows the detection of
fluorescence to start just after auto-fluorescence has completely decayed. This guarantees very sensitive
tests with a low limit of detection (LOD).
Since this process takes place in 0.5 ms, the read-out time of the test by the instrument takes only a few
seconds.
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