The lateral-flow immunoassays based on novel fluorescent labels have been receiving increasing attention. Creative Biolabs is a full-service company specializing in the design of ultra-sensitive quantitative diagnostic assays for in vitro diagnostics (IVD) research use. Our precisely engineered quantum dot (QD)-based immunochromatographic assays offer improved assay sensitivity and reliability. By using QDs as a label, our patented fluorescent conjugation technology combined with years of experience allow us to create high sensitivity diagnostic assays in the most difficult of matrices. We are competent to offer fully customizable quantum dot-based immunochromatographic assay (QICA) for worldwide customers.
The use of labels such as fluorescent markers in immunochromatographic assay contributes to decrease the detection limit and decrease the influence of the matrix. Several studies have reported low detection limits for assays based on fluorescent nanoparticles. QDs are semiconductor nanocrystals whose diameter varies from 2 to 10 nm. Their fluorescence emission peak strongly depends on their size as well as their composition. Water-soluble QDs have a surface coating enriched with carboxyl or amine groups, thus facilitating their conjugation with antibodies. LCS is a powerful tool enabling low-cost on-site and rapid detection. In comparison with organic fluorescent labels, QDs represent a new type of fluorescent nanocrystal and are considered as ideal labels for LCS use due to their unique properties, such as broad adsorption, narrow and symmetric photoluminescence spectra, resistant to photobleaching, strong luminescence and robust photostability. These excellent properties render QDs as robust reporters for developing highly sensitive LCS assays capable of simultaneous quantification of multiple analytes.
Immunoglobulins of type E (IgE) plays an important role in allergen recognition and the initiation of allergic reactions. In the case of allergic disease or myeloma, the IgE content in blood is increased 4-30 fold. Therefore, methods for determining the total IgE concentration are necessary for primary care providers to assess the state of the immune system.
Fig.1 Schematic of QD-based LCS for IgE detection. (Liang, 2020)
Procalcitonin (PCT) is an indicator for the evaluation of severe sepsis caused by bacterial infection. The traditional methods for PCT biomarker detection such as immunoturbidimetry, enzyme-linked immunosorbent (ELISA) and electrochemical luminescence immunoassay are reliable and sensitive, but require expensive instruments, well-trained operators, and are not suitable for point-of-care (POC) diagnostic tests in field detection. The study once reported that a highly luminescent quantum dot bead (QB) was synthesized and used to improve the sensitivity of LCS for quantitative PCT detection. Fig.2 shows the sandwich procedure for the detection of PCT by using the QB-based LCS platform.
Fig.2 Schematic representation of the sandwich procedure for the detection of PCT. (Zhou, 2020)
Tetanus possesses a high infection rate and remains a leading cause of infection in some developing countries. To reduce tetanus infection, POC monitoring of the serum tetanus antibody level is highly desired. By using a sandwich immunoreaction, the QICA is easily prepared via the formation of a sandwich structure complex of QD-labeled goat anti-human IgG (Fc)-tetanus antibody-tetanus antigens. The assay can be completed in 30 min with a detection limit of 0.001 IU mL−1.
Fig.3 Principle of the QD-Based LCS for tetanus antibody detection. (Wang, 2019)
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