Sensitive Quantification of Cyclic Citrullinated Peptide Using Metal-Enhanced Fluorescence Nanoparticles

Abstract

Rheumatoid arthritis (RA) is a chronic autoimmune disease, which causes severe damage to the joints and leads to serious mobility impairment. Because there are many complications of RA, it is important to make a correct diagnosis and start treatment before significant joint damage progress. One of the most useful biomarker for early diagnostics of RA is anti-cyclic citrullinated peptide antibodies (anti-CCP). These are considered highly specific for RA in comparison with Rheumatoid Factor (RF), so that the required test systems have been continuously optimized in the past years. Currently, enzyme-linked immunosorbent assay (ELISA) is a conventional method for anti-CCP detection. Although ELISA is a convenient technology, poor limit of detection (~25 U/mL) and high background noise remain problems. Here-in, I have improved the sensitivity using metal-enhanced fluorescence nanoparticles and microarrays on dendron modified surface. In this work, I suggested new approaches for enhanced analysis of anti-CCP by introducing metal-enhanced fluorescence (MEF) nanoparticles to the microarray platform. To detect anti-CCP, I immobilized CCP peptide on dendron-coated glass slide and used fluorescence labeled anti-human antibody. Additionally, commercially available fluorescence enhanced polystyrene beads have been applied to the microarray system. In the system MEF nanoparticles resulted in 3 to 5 times higher fluorescence intensity than a typical dye Cy5 and lowered the detection limit to 10 U/mL. For polystyrene beads, signal intensity was 7 times higher than Cy5 and the limit of detection was 5 U/mL. This approach is expected to be a useful tool for early RA diagnosis that can detect low concentration of anti-CCP.