Highly sensitive electrochemical immunosensor based methylene bluereduced graphene oxide nanocomposites as signal probe for IL-6 detection in gingival crevicular fluid samples

Changfeng Zhu ¹ Hongxin Wang ² Jiyang Liu ^2*

• ¹ Beijing Hospital of Integrated Traditional Chinese and Western Medicine, Beijing, China
• ² Zhejiang Sci-Tech University, Hangzhou, China

As a kind of important inflammatory cytokines, interleukin-6 (IL-6) can mediate the entire pathological process of periodontitis and are closely associated with the degree of inflammation. Therefore, it is critical to develop convenient quantitative methods for monitoring the IL-6 amount in gingival crevicular fluid. In this study, methylene blue (MB) decorated reduced graphene oxide (rGO) are employed as signal probe and further supported the antibody enabling specifical recognition of IL-6. Due to the π-π stacking and electrostatic interactions, rGO-MB nanocomposites can be stably obtained. rGO with the characteristics of good conductivity and large surface area promotes the redox signals of MB on the glassy carbon electrode (GCE). In addition, through simple self-polymerization in situ of dopamine, the obtained polydopamine (PDA) can be not only directly used as a biological crosslinking agent for covalent immobilization of anti-IL-6 antibody, but also regarded as a protective layer to enhance the stability of rGO-MB on the GCE surface. Such designed PDA/rGO-MB/GCE based immunosensor enables the specific binding with IL-6 and produces the decreased electrochemical signal of MB, realizing the selective and sensitive quantitative measurement of IL-6. As a consequence, our fabricated PDA/rGO-MB/GCE based electrochemical immunosensor performs an excellent linear relationship with IL-6 ranging from 1 pg/mL to 100 ng/mL and the limit of detection is as low as 0.48 pg/mL. Moreover, our as-prepared sensing strategy shows accurate monitoring of IL-6 amount in gingival crevicular fluid samples.