Microdevice immunoassay with conjugated magnetic nanoparticles for rapid anti-cyclic citrullinated peptide (anti-CCP) detection.

Anti-cyclic citrullinated peptide IgG antibodies (anti-CCP) are produced as an immune response in the presence of post-translational modified peptides known as cyclic citrullinated peptides (CCP). Anti-CCP have been considered as specific biomarkers for the diagnosis of rheumatoid arthritis (RA), and due to their high specificity, it is possible to make a differential diagnosis of other rheumatic diseases. These autoantibodies can be detected in the early stages of RA and even up to 10 years before presenting the first symptoms of the disease opening a window of opportunity for timely treatment. In this work, a simple straight channel microdevice and CCP conjugated magnetic nanoparticles (MNPs-CCP) as solid support was developed for quantifying anti-CCP. An additional microdevice with an optical flow Z cell design coupled with optical fibers was used to perform the spectrophotometric detection. The dynamic range of concentrations was determined between 0.70 and 2000 U mL with a limit of detection of 0.70 U mL. The developed microdevice immunoassay was probed using a positive control and a negative control of plasma employing only 6 μL of both samples and reagents. The results showed that the proposed microdevice was almost nine times faster than using a commercial anti-CCP ELISA kit obtaining equivalent results and being 16 times more sensitive. The microdevice immunoassay, with conjugated MNPs-CCP is a simple method for anti-CCP quantification being cheaper, faster, and more sensitive than the ELISA kit.