Lateral Flow Application

Lateral Flow Assays (LFA) are part of the Point of Care Testing (POCT) or bedside testing. LFAs are primarily intended for the clinical analysis of biological samples such as plasma, urine, and saliva.  This test allows the early diagnosis of many diseases and infections to guide the choice of treatment.  The application of LFAs also extends to areas such as agriculture, food, environmental safety, and veterinary medicine.

Our Bright-Dtech™ technology bring a more sensible (high brightness resulting in an improved limit of detection) and stable (high photo-stability over days or weeks, resistance to photo-bleaching and durable signal intensity) approach.

The Bright-Dtech™ LFA tests are based on the migration of detection bioreceptors conjugated to fluorescent nanoparticles along the strip for analytes detection. The resulting signal intensity at the control and test lines is measured by a time-resolved fluorescence reader. This method allows to increase the sensitivity and quantify the targeted analyte.

Required material : Time-Resolved Fluorescence microplate reader.

Why using Bright-Dtech™ for Lateral Flow Applications?

Our technology brings benefits to users. Thanks to Bright-Dtech™ LFA there is a very low background and an exceptional lifetime so no photobleaching. We have also a low LOD, LOQ and a low hands-on time. Its important to know that Bright-Dtech LFA allows quantitative and semi-quantitative analysis.

Serologic Test

Serological LFAs are used for the detection of targeted antibodies (IgG, IgM, or total) in blood samples. The conjugate pad contains Bright-Dtech-conjugated antigen or Bright-Dtech-conjugated rabbit IgG. Anti-IgG or anti-IgM antibodies are striped on the test line, while anti-rabbit IgG antibodies are striped on the control line.

Antigenic test

Antigenic tests are used for the detection of a target analyte in a sample (urine, saliva, sweat, etc.). These tests are run according to two formats: sandwich and competitive.

In a sandwich assay, analytes are captured between the Bright-Dtech-conjugated antibody and the capture antibody located on the test line. This strategy is adapted to the detection of large analytes (> 1 KDa) containing at least two distinct epitopes, thus two binding sites. In this case, the signal obtained on the test line is proportional to the amount of target in the sample.

Competitive formats are typically used to test small molecules with unique antigenic determinants, which cannot bind to two antibodies simultaneously. In this assay, the test line contains the target analyte. The conjugate pad contains Bright-Dtech-conjugated antibodies able to recognize the analyte on the test line and in the sample. If the target is in the sample, it will bind to the detection bioreceptor and prevent its binding to the test line. The signal obtained in a competitive assay is inversely proportional to the amount of analyte present in the sample.

Example: LFA for SARS-CoV-2 nucleoprotein detection in sandwich format

This assay detects and quantifies human SARS-CoV-2 nucleoprotein in samples (serum, plasma, or saliva). The sample is first treated with the running buffer before being loaded on the sample pad. The running buffer defines the optimal conditions for the detection of the analyte. Then, the sample migrates to the conjugate pad where the Bright-Dtech-conjugated antibodies are immobilized. Wetting of the conjugate pad allows the release of the detection bioreceptor and the first interaction with the SARS-CoV-2 nucleoprotein. The resulting nucleoprotein-antibody-labelled complex reaches the nitrocellulose membrane. The test line consists of an antibody against the SARS-CoV-2 nucleoprotein, while the control line is composed of species-specific antibodies. After 15min of sample migration, the fluorescent signal emitted at the control and test line is measured using a time-resolved fluorescence reader. The fluorescent signal is proportional to the amount of target in the sample.

Our lateral flow kit allows detection and quantification of the SARS-CoV-2 nucleoprotein in only 20 minutes. We have shown that Bright-Dtech technology can significantly enhance SARS-CoV-2 nucleoprotein detection thanks to the exceptional brightness of our fluorescent nanoparticles.

Our customized Bright-Dtech™ technology is available for all matched antibody pair developed for classical sandwich ELISA allowing accurate detection and high signal/noise ratio for reliable results.

Figure 1. Images of the test strips for detecting SARS-CoV-2 nucleoprotein.

Bright-Dtech™ based lateral flow assay obtained with a time-resolved fluorescence plate reader. Fluorescence signal is visible from 250pg/mL to 1000pg/mL. Clear and consistent control lines are visible.

Figure 2. Quantitative detection of SARS-CoV-2 nucleoprotein.

Results demonstrate a very low/significant limit of detection of SARS-Cov-2 (LOD = 0.075ng/mL using 3 standard deviation).

Bright-Dtech™ technology enhances the detection of nucleoprotein due to its high specificity and sensitivity given by the time-resolved fluorescence signal.