How Fluorescence Immunochromatography (FICT) Works¶
FICT (Fluorescence Immunochromatographic Technology) is a quantitative lateral-flow immunoassay. This page explains the mechanism in plain language — what happens inside the cartridge between sample application and result.
The Signal Chain, Step by Step¶
- Capture antibody is immobilized on a nitrocellulose membrane at the test (T) line.
- Detection antibody, conjugated to a fluorophore, is dried on the conjugate pad.
- Sample (serum/plasma/whole blood) is applied; capillary action carries it forward.
- Sandwich complex forms: capture antibody — analyte — fluorophore-labeled detection antibody.
- Excitation light excites the fluorophore at the T line.
- Emission is collected by a photodetector and converted to concentration.
The Sandwich Immunoassay¶
The analyte is "sandwiched" between two antibodies. The more analyte present, the more fluorophore-labeled antibody binds at the T line — and the brighter the fluorescence.
Why Fluorescence → Quantitation¶
| Property | Consequence |
|---|---|
| Fluorescence intensity ∝ analyte concentration | Enables a numerical result |
| Wide dynamic range (3–4 logs) | Measures low and high values without dilution |
| Instrument readout (not eye) | Removes operator judgment variability |
From Signal to Number¶
The analyzer: 1. Excites the T line at a specific wavelength (e.g., 365 nm). 2. Measures emitted light (e.g., 615 nm). 3. Converts intensity to concentration using the pre-loaded standard curve.
FAQ¶
What is the difference from a pregnancy-test-style strip? Those are colloidal-gold and read by eye (line present/absent). FICT is fluorescence read by an instrument, giving a number.
Why does FICT need a dedicated analyzer? The fluorophore must be excited and its emission measured precisely — only a calibrated fluorometer can do this.
For the full technical treatment, see the Research Center white paper.
Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.