This document describes lateral flow immunochromatographic assays (ICA), which are simple devices used to detect the presence or absence of a target analyte. ICA strips, also known as test strips, contain four main components: a sample application pad, conjugate pad, nitrocellulose membrane, and adsorbent pad. The principle of the sandwich assay used in ICA strips involves a labeled antibody bound to the target analyte being captured at the test line by an immobilized antibody, while a control line captures any unbound labeled antibody.

1. LATERAL
FLOW IMMUNOCHROMATOGRAPHIC
ASSAYS (ICA)
DR. AMAN ULLAH
B.SC. MLT
PH.D. MICROBIOLOGY

2. INTRODUCTION
• Immunochromatography assay (ICA), namely lateral flow test, is
a simple device intended to detect the presence or absence of the
target analyte
• The concept of immune-chromatography is a combination of
chromatography and immunochemical reactions
• The most widespread immunochromatographic system is the test
strip

3. ICA OR ICT STRIPS ALSO KNOWN AS
DEVICE

4. COMPONENT OF ICT STRIP

5. COMPONENT OF ICT STRIP
• There are four main components of ICT Strips
1. Sample Application Pad
2. Conjugate Pad
3. Substrate(Nitrocellulose) Membrane
4. Adsorbent Pad

6. SAMPLE APPLICATION PAD
• Made of cellulose and/or glass fiber and sample is applied on it
• Its function is to transport the sample to other components
• Sample pad should be capable of transportation of the sample in
a smooth, continuous and homogenous manner
• This pretreatment may include separation of sample
components, removal of interferences, adjustment of the pH, etc.

7. CONJUGATE PAD &
SUBSTRATE(NITROCELLULOSE)
MEMBRANE
• Conjugate pad: The place where labeled antibodies, usually
nano colloid gold particle are dispensed
• Material of conjugate pad should immediately release labeled
conjugate upon contact with moving liquid sample
• Nitrocellulose membrane: Test and control lines are drawn
over the Nitrocellulose membrane by immobilizing the capture
antibody onto the strip membrane

8. ADSORBENT PAD
• It works as sink at the end of the strip
• It also helps in maintaining flow rate of the liquid over the
membrane
• It stops back flow of the sample
All these components are fixed or mounted over a backing card,
which serves as a support and it makes easy to handle the strip

9. PRINCIPLE OF SANDWICH ASSAY
• In this assay format, label antibody is immobilized at
conjugate pad
• This is a temporary adsorption which can be flushed away by
flow of any buffer solution
• A capture antibody against target analyte is immobilized over
test line
• A secondary antibody against labeled antibody is immobilized
at control zone

11. INTERPRETATION OF THE RESULT

13. QUESTIONS/SUGGESTIONS
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