A flexible gradient lateral flow immunochromatographic assay for qualitative, semi-quantitative, and quantitative determination of serum amyloid A

Guangtian Yang; Jishun Li; Shenglan Zhang; Huixiang Ouyang; Chunhai Jiang; Hongcheng Pan

doi:10.1016/j.jim.2023.113574

A flexible gradient lateral flow immunochromatographic assay for qualitative, semi-quantitative, and quantitative determination of serum amyloid A

J Immunol Methods. 2023 Dec:523:113574. doi: 10.1016/j.jim.2023.113574. Epub 2023 Oct 24.

Authors

Guangtian Yang¹, Jishun Li¹, Shenglan Zhang¹, Huixiang Ouyang¹, Chunhai Jiang¹, Hongcheng Pan²

Affiliations

¹ Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China.
² Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China. Electronic address: panhongcheng@glut.edu.cn.

PMID: 37884205
DOI: 10.1016/j.jim.2023.113574

Abstract

Serum amyloid A (SAA) is an acute-phase protein produced in response to inflammatory proteins during infections, inflammation, trauma, surgery, cancer, and other conditions. Early and accurate detection of SAA is necessary for diagnosis and monitoring of disease progression. To meet this need, we developed a gradient lateral flow immunoassay test strip using Au nanoparticles as signal reporters. The test strip has three test (T1, T2, and T3) lines with progressively decreasing concentrations of SAA antibody, enabling the determination of high, medium, and low concentrations of SAA in serum. The test strip results were analyzed using three distinct readout methods, each with different sensitivity, accuracy, and precision for SAA concentration measurements. Qualitative judgment is based on the color of the T1 line. Semi-quantitative assessment of SAA concentration is determined by the number of colored T-lines. Specifically, color development in T1 line alone indicates a concentration range of 10-50 μg/mL, while T1 and T2 lines together indicate a range of 50-100 μg/mL, and development in all three lines (T1, T2, and T3) indicates a concentration of >100 μg/mL. Quantitative analysis was performed using either smartphone imaging or image scanning with ImageJ software. By using a five-parameter logistic function, we found a strong correlation (R² = 0.998) between the ratio of signal intensities of (T1 + T2 + T3) to the control (C) line and SAA concentrations ranging from 5 to 1000 μg/mL. At lower concentrations (0-100 μg/mL), we observed a proportional relationship between the value of (T1 + T2 + T3)/C and SAA concentration. The limit of detection for SAA was 9.33 ng/mL (or 6.53 μg/mL of SAA in undiluted serum samples) for the smartphone method and 3.06 ng/mL (or 2.14 μg/mL of SAA in undiluted serum samples) for the scanner method. The gradient test strip was highly consistent with a commercially available SAA immunochromatographic test strip when tested with real human serum samples. Passing-Bablok regression indicated that results obtained using the smartphone app and scanner methods of the gradient test strip were comparable to those obtained using the commercial test strip. The gradient test strip is flexible and adaptable, providing solutions for qualitative, semi-quantitative, and quantitative SAA measurements.

Keywords: Gradient lateral flow immunoassay test strip; Quantitative analysis; Serum amyloid A.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Antibodies, Monoclonal
Gold
Humans
Immunoassay / methods
Metal Nanoparticles*
Serum Amyloid A Protein*

Substances

Serum Amyloid A Protein
Gold
Antibodies, Monoclonal