Abstract
Despite the widespread application of point-of-care lateral flow tests, the viscosity dependence of these assay results remains a significant challenge. Here, we employ centrifugal microfluidic flow control through the nitrocellulose membrane of the strip to eliminate the viscosity bias. The key feature is the balancing of the sample flow into the cassette of the lateral flow test with the air flow out of the cassette. A viscosity-independent flow rate of 3.01 ± 0.18 µl/min (±6%) is demonstrated for samples with viscosities ranging from 1.1 mPas to 24 mPas, a factor greater than 20. In a model human IgG lateral flow assay, signal-intensity shifts caused by varying the sample viscosity from 1.1 mPas to 2.3 mPas could be reduced by more than 84%.
Highlights
Lateral flow tests (LFTs) are one of the most common point-of-care tests
By using a model LFT assay, we show the viscosity bias and demonstrate for the first time experimentally how it can be eliminated by employing pneumatic flow control in the centrifugal cassette
Varying sample viscosities are a challenge for quantitative LFTs because the flow rate through the strip depends on the sample viscosity
Summary
Lateral flow tests (LFTs) are one of the most common point-of-care tests. A variety of different samples can be used, such as whole blood[1], serum[2], urine[3], saliva[4], milk[5], and many more[6,7,8]. The strips consist of different porous materials that are glued in series on a backing card. The applied sample is wicked through the strip by capillary forces. Each lateral flow strip has a functionalized site on the chromatographic membrane, generally in the form of a test line. At that site, binding reactions take place between analytes and detection molecules. The formation of the test line on the strip signifies the presence or absence of an analyte in the sample. LFTs often allow qualitative or semiquantitative readouts with the naked eye and are a versatile tool for field applications
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