The conjugate release pad is the second step in a lateral flow assay (LFA). It holds and preserves the detection reagents, or conjugate. As the sample flows through the conjugate release pad, the conjugate is released into the sample and binds with the target molecule, if present. The sample and conjugate then flow together to the test membrane. To ensure consistent performance, the conjugate must dry without damage or aggregation and release rapidly when the sample comes into contact with it.

Whatman™ conjugate release pads do not require treatment prior to conjugate application, as they are inherently hydrophilic. The open structure of the material allows rapid penetration by both conjugate and sample.

Key considerations:

  • Water absorption: as an assay developer considers how many conjugate particles are needed to perform the test, water absorption determines the density of conjugates which in turn determines pad size needed to ensure the correct amount of conjugate is fed into conjugate release pad.
  • Thickness: determines water absorption capacity.
  • Wicking rate: this determines how fast the mixture of conjugate and sample migrate through the conjugate pad. Slower wicking will allow for more interaction time between conjugate and sample, but the downside is it also allows more time for unspecific interactions that may occur. The wicking rate also contributes to the overall test time.
  • Conjugate release rate: the percent of the conjugate that will be released from the pad in a given time. This helps determine how much conjugate needs to be embedded into the pad for a reliable test.
10 Top Tips for lateral flow assay development

The Whatman™ advantage

  • High conjugate release levels reduce both waste and reagent costs.
  • As more conjugate gets to the capture line, capture line intensity increases for improved assay sensitivity.
  • Naturally hydrophilic material rewets rapidly every time for improved test consistency.
Grade
 Properties
 Thickness
(um @ 53kPA)
 Water absorption
(mg/cm2)
 Percent release of gold conjugate (after 90 s)
Standard 14
 Untreated bound glass fiber for faster flow than cotton with lower sample retention. Higher absorption capacity than Standard 17.
 355 55 75
Standard 17
 Untreated bound glass fiber for faster flow than cotton with lower sample retention. Greater tensile strength than Standard 14.
 370 35 75
Fusion 5
 Fusion 5 can perform all of the functions of a lateral-flow strip. It can be used as sample wick as well as a blood separator with excellent separation efficiency.
 370 42.3 > 94
Rapid 24
 Treated bound glass fiber, high absorption capacity.
 340 55 89
Rapid 27
 Treated bound glass fiber has greater tensile strength than Rapid 24.
 365 35 86
Accuflow G
 Pretreated pad, medium absorption capacity.
 370 40 89

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