A novel oriented immunosensor based on AuNPs-thionine-CMWCNTs and staphylococcal protein A for interleukin-6 analysis in complicated biological samples.

Interleukin-6 (IL-6) is of high importance for disease diagnosis and prognosis in human health since it's a crucial component in immune homeostasis, hematopoiesis, and metabolism. Herein, an immunosensor has been developed for monitoring IL-6, which is fabricated by Au nanoparticles (Au NPs)-thionine (THI)-carboxylated multi walled carbon nanotubes (CMWCNTs) as the substrate with high conductivity. Staphylococcal protein A (SPA) could directionally capture antibody to reduce steric hindrance caused by random immobilization. Built upon the high efficiency of IL-6 antibody immobilization by the SPA on the sensing surface, the immunosensor exhibited a favorable activity for IL-6 detection. Under optimal conditions, the biosensor presented a LOD of 2.87 pg mL-1 and a wide linear range from 0.01 ng mL-1 to 800 ng mL-1 in serum samples. Furthermore, the assembled sensor successfully quantified the IL-6 concentration in serum and different tissue lapping liquids (lung, heart, liver) from rats with myocardial infarction. The satisfactory performance of the proposed sensor not only broadens its application in clinical monitoring of IL-6 but also provides a novel approach to study inflammation in rats.