In qualitative tests, the result is a simple, “yes or no”, visualized by colored capture line(s). One of the earliest examples of this assay is the pregnancy test, a one-step lateral flow chromatographic immunoassay.

Several types of tests have been created:

• Monotest monochromatic (same colour line for the analyte and the control test)
• Monotest bichromatic (two colour lines, one for the analyte and one for the control test)
• Multitest monochromatic (same colour line for analytes and the control test
• Multitest polychromatic (several colour lines, one for each analyte and one for the control test)

This method employs a colored conjugate (mouse anti-hCG monoclonal antibody + colored Dyed Estapor® Microspheres complex) which is pre-dried on the test strip. (Sample pad)

When a sufficient sample volume is added, the conjugate selectively reacts with hCG in the test samples, with a high degree of sensitivity, forming an antibody-antigen complex. The mixture then moves upward on the membrane arriving at the test zone by capillary action producing a blue band.

In the absence of hCG, there is no line in the test zone. The reaction mixture continues flowing through the absorbent device to the immobilized antibody placed in the control band region and a red band appears (control band), regardless of the presence of hCG.

Some industrial applications

The development of “relatively” simple and rapid detection tests using lateral flow technology meets the need for POC testing in the fields of Clinical and Veterinary Diagnostics, Environmental Screening and Food Testing. There are several tests already on the market in these application areas as indicated below.

• In Clinical and Veterinary diagnostics: Pregnancy test, HIV tests, Drugs of abuse, Infectious disease (Adenovirus, Helicobacter Pylori, Rotavirus etc.), Tumor markers
• In Food industry: Salmonella, E.Coli, Listeria tests
• In Environment: Legionella or Amibia tests

Benefits:

• Visualized coloration
• Faster time to result
• Easy to use

In a qualitative test, we can choose several assay types:

Multichromatic / multiparametric test
One example is the influenza virus test

In Lateral Flow, Estapor® recommands the use of Dyed Estapor® Microspheres.

These microspheres are also extremely uniform and are dyed internally such that their surface properties are unchanged insuring maximum color brilliance and preventing dye leaching in water or aqueous buffers. We offer more than 100 dyed microspheres (red, blue, green, black, yellow). This well known effect is called the Rainbow Effect.

The possibility to incorporate colored dye into our uniform microspheres greatly enhances their interest and utility in some tests and opens up new frontiers for applications in the diagnostics, life sciences, biotechnology, electronics or environment fields.

Custom Development of Dyed Microspheres
If you are looking for dyed microspheres which are not available from our standard menu, Estapor® microspheres can provide custom development for the Diagnostic, the Biotech and the Pharmaceutical industries. Our experience in dyed microsphere(s) development allows our technical department to quickly and inexpensively produce(s) custom microspheres to fit your very specific requirements. Please send your detailed custom requirements to your Estapor® representative. You don't have to search any further for a potential source of dyed microspheres.