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Surfactants Selection Guide for Lateral Flow Assays

Surfactants Selection Guide for Lateral Flow Assays
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Surfactants Selection Guide for Lateral Flow Assays - 1

Application Highlight June, 2022 Keywords: UniSart® Membrane, Lateral Flow Assay, Surfactants Surfactants Selection Guide for Lateral Flow Assays Dr. Shuo Liang Sartorius Stedim Biotech GmbH, August-Spindler-Strasse 11, 37079 Goettingen Correspondence E-Mail: shuo.liang@sartorius.com Introduction Lateral flow assays (LFA) are a type of immunographic assay widely used for the rapid detection of pathogens, toxins, environmental contaminants, etc. Their ease of use and accuracy make these assays well suited for the point-of-care market. For purposes of this study, three lateral flow tests were selected. The effects of surfactants on test performance were demonstrated by adding different surfactants (surface active agent) during the pre-treatment of sample pads.

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1. Classification of surfactants and their function in lateral flow assay: Figure 1: Different forms of surfactants (Surface Active Agent) Function in Lateral Flow Assay Enhance or decrease the test line intensity Accelerate or decelerate the background clearance + Reduce the unspecific binding Increase wettability of the pad material

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As listed in Table 1 the following surfactants were selected. All surfactants were used as additives in pre-treatment of samples pads of the lateral flow tests. Table 1. Overview of surfactants used for this study Commercial Name Performance optimization Gentle surfactant Background clearance and conjugate pad release Background clearance and conjugate pad release Protein solubilization Commonly used in protein chemistry SDS (sodium dodecyl sulfate) Gentle surfactant and commonly used in LFA HLB: hydrophilic-lipophilic balance, high value hydrophilic (water soluble), low value hydrophobic...

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2. Effect of different surfactants on the performance of UniSart® diagnostic membranes 2.1 hCG pregnancy test: an example for impacts of surfactants on signal intensity and background clearance The hCG test is known to be robust and highly reproducible. Thus, it was selected to demonstrate the effects of surfactants on signal intensity and background clearance. The surfactants listed in Table 1 were applied in three categories of concentration: Low concentration: ≤ 0.1 % (w/w) or (v/w), moderate concentration: 0.2-0.5 % (w/w) or (v/w), and high concentration: ≥ 0.5 % (w/w) or (v/w). The...

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For non-ionic surfactants, the application of Brij 35, Brij 58, Tergitol™ type NP-40, and IGEPAL® CA-630 generated good test performance at all ranges of concentration tested. Tween 20 could be used at low and moderate concentration, whereas Tween 60 is only recommended at moderate concentration. At high concentration, both Tween surfactants resulted in false positive signals. A possible explanation would be that the high concentration of Tween surfactants adsorbed on the surface of gold-nanoparticles and disrupts the adsorption of conjugate-antibodies2. The zwitterionic surfactant CHAPS...

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2.3 Protein G and protein A test: an example for surfactants’ effect on the interaction of carrier proteins and antibodies Protein G and protein A are commonly used in lateral flow assays to enhance the sensitivity. Both proteins interact with the Fc fragment of the antibody. It allows for better binding of the detection protein to the membrane surface. In such test, protein G/A-antibody complex is immobilized on the nitrocellulose membrane via protein G/A. Therefore, analysis of protein G/A on membrane immobilization and their interaction with antibodies are important for the optimization...

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Conclusion The effect of surfactants on test performance varied depending on the assay and the membrane, but also the type and concentration of surfactant used. Production costs must be considered if using a surfactant at high concentrations. It is therefore recommended to screen a variety of surfactants and concentrations to ensure the best performance. Additional reading: 1. L. Zeng et al., Development of ic-ELISA and lateral-flow immunochromatographic strip for detection of vitamin B2 in an energy drink and vitamin tablets, Food and Agricultural Immunology, (2018) 29:1, 121-132. 2. Y....

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Germany Sartorius Lab Instruments GmbH & Co. KG Otto-Brenner-Strasse 20 37079 Goettingen Phone +49 551 308 0 For additional information visit www.sartorius.com Specifications subject to change without notice. Copyright Sartorius Lab Instruments GmbH & Co. KG. Status: 06 | 2022

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