Quantitative lateral-flow immunoassay for the assessment of the cartilage oligomeric matrix protein as a marker of osteoarthritis

This study reports a simple and quantitative analytical method for detecting cartilage oligomeric matrix protein (COMP) using a lateral-flow immunoassay (LFI) format. An immuno-chromatographic assay was developed using a gold nanoparticle (AuNP)-conjugated monoclonal antibody (Ab) probe for the quantitative detection of COMP in human synovial fluid (SF). The detection antibody was conjugated with the AuNP (similar to 30 nm) to enable detection, and the capture antibody was immobilized within a multi-spot pattern in the test zone of a membrane strip. COMP in the human SF binds to the AuNP-conjugated detection antibody, and the COMP-Ab complex then binds to the capture antibody. The immunoassay test can be analyzed by visualizing the test strip with a commercial scanner and an imaging software program. The color density of the multi-spot pattern at the test zone increased in proportion to the concentration of COMP. The developed immunoassay exhibited a dynamic detection range from 0.6 to 20 mu g/mL of COMP. The detection limit of the proposed LFI system was approximately 0.2 mu g/mL. The test results showed good correlation with those obtained using a conventional enzyme-linked immunosorbent assay (ELISA) to detect COMP. We expect that the proposed immunoassay method, based on the quantification of COMP, is suitable for osteoarthritis diagnosis using SF samples.