Development of a Microcolumn One-Site Immunometric Assay for a Protein Biomarker: Analysis of Alpha1-Acid Glycoprotein in Serum

Authors

Chenhua Zhang, University of Nebraska - Lincoln
Shae Lott, University of Nebraska - Lincoln
William Clarke, John Hopkins University School of MedicineFollow
David S. Hage, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

2019

Citation

Chenhua Zhang , Shae Lott , William Clarke , David S. Hage , Development of a Microcolumn One-Site Immunometric Assay for a Protein Biomarker: Analysis of Alpha1-Acid Glycoprotein in Serum, Journal of Chromatography A (2019)

Comments

© 2019 Published by Elsevier B.V.

doi: https://doi.org/10.1016/j.chroma.2019.460558

Abstract

A one-site immunometric assay based on affinity microcolumns was developed for the analysis of alpha₁-acid glycoprotein (AGP) as a model protein biomarker. In this assay, a sample containing AGP was incubated with an excess amount of a labeled binding agent, such as fluorescein-labeled anti-AGP antibodies or F_ab fragments. The excess binding agent was removed by passing this mixture through a microcolumn that contained an immobilized form of AGP, while the signal was measured for the binding agent-AGP complex in the non-retained fraction. Theoretical and practical factors were both considered in selecting the concentration of labeled binding agent, the incubation time of this agent with the sample, and the application conditions for this mixture onto the microcolumn. The effects of using various labeling methods and intact antibodies vs F_ab fragments were also considered. The final assay was performed with fluorescein-labeled anti-AGP antibodies and a 2.1 mm i.d. × 1.0 cm AGP microcolumn operated at 0.30 mL min^-1. This method required only 1 μL of serum, had a detection limit of 0.63 nM AGP, and gave a potential throughput of 2 min per sample. This assay was used to measure AGP in normal serum and serum from patients with systemic lupus erythematosus, giving good agreement with the literature and a reference method. The same approach and guidelines can be used to create assays for other protein biomarkers by changing the labeled binding agent and immobilized protein within the microcolumn.