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Updated: May 10, 2025
Author Spotlight: High-Quality Quantum Dot Nanobeads for Sensitive Fluorescent Lateral Flow Immunoassays
Published on: June 28, 2024
Colorimetric-fluorescent dual-mode background fluorescence-quenching lateral flow immunoassay: Principle, modeling,
Wenlin Zhao1, Jishun Li2, Shenglan Zhang3
1Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin, 541004, China.
Abstract:
Conventional lateral flow immunoassays (LFIAs) face challenges in competitive detection of small molecule antigens, including inverse correlation between signal and analyte concentration and insufficient sensitivity. Background fluorescence quenching lateral flow immunoassay (BF-LFIA) offers a novel solution, but quantitative models to guide quencher design and sensitivity optimization are lacking. This study developed a dual-mode colorimetric-fluorescent BF-LFIA for highly sensitive folic acid (FA) detection using polystyrene-encapsulated ZnS@CdSe quantum dots (QDs) as background fluorophores and gold nanorods (AuNRs) or gold nanoparticles (AuNPs) as quenchers. Based on the inner filter effect (IFE) and heterogeneous capture reaction kinetics, we constructed a mathematical model for this dual-mode BF-LFIA. Under quasi-steady-state approximation, analytical expressions relating FA concentration to colorimetric and fluorescent signals were derived, enabling quantitative description of calibration curves for both modes. Due to higher molar extinction coefficients at excitation and emission wavelengths, AuNRs as quenchers exhibited superior sensitivity compared to AuNPs, achieving limits of detection of 0.14 ng/mL and 0.15 ng/mL for colorimetric and fluorescent modes, respectively. The mathematical model showed good agreement with experimental results. The derived calibration curve equations demonstrated better fitting goodness and residual normal distribution characteristics compared to conventional four-parameter logistic equations. Passing-Bablok regression analysis confirmed good consistency and comparability between the dual-mode BF-LFIA and a commercial FA fluorescent immunoassay kit. This study provides theoretical foundations for understanding dual-mode BF-LFIA principles and guiding optimization, offering new strategies for highly sensitive rapid detection of small molecules and other biomarkers.
