Diagnosing the complex activation factor in rheumatoid arthritis on nanomaterial-modified ELISA

Rheumatoid arthritis (RA) is a common inflammatory disease that causes functional disability and joint deformity. In RA, the immune system attacks the lining of the joints and tissues of the body. RA generally affects the ankles, hands, and knees. An early diagnosis of RA is imperative for a greater chance of remission and disease control. Various biomarkers have been discovered for diagnosing and treating RA. Among them, interleukin-6 (IL-6) has been established as a biomarker as an increment in its levels was found in RA patients. In this research, a nanomaterial-modified improved enzyme-linked immunosorbent assay (ELISA) was developed to quantify IL-6 levels in spiked human serum samples. Multiwalled carbon nanotube (MWCN) was used to modify the ELISA polystyrene (PS) surface by amine linkers, and then a probe of antibody-gold nanoparticle (GNP)-aptamer was attached onto the MWCN. The probe molecule was created by immobilizing the antibody and aptamer on the GNP. It enhanced the detection of IL-6 and performed better with only antibodies. The absorbance was increased with increasing IL-6 levels, and the detection limit was calculated to be 0.25 pg/mL [y = 0.0636x - 0.0361; R 2 = 0.9907] in 10 mM PBS buffer (pH 7.4) and IL-6 spiked serum with the R2 value of 0.9907. Furthermore, experiments with relevant proteins as control namely cyclic citrullinated peptide and matrix metalloproteinases, did not show any absorbance increments signifying the specific detection of IL-6. This IL-6 biosensor quantifies the IL-6 and diagnoses RA and its conditions.