A Disposable Label-Free Voltammetric Immunosensor for Sensitive Detection of Interleukin-6.A Disposable Label-Free Voltammetric Immunosensor for Sensitive Detection of Interleukin-6

Interleukin-6 is a soluble mediator with a pleiotropic effect on human health. High concentrations of IL-6 are correlated with a wide range of diseases as well as in the hyper-inflammatory responses and autoimmune processes. Recently, IL-6 has been indicated as a prognostic inflammatory marker to monitor patients affected by COVID-19 infection. Here, we report the fabrication of a novel label-free electrochemical immunosensor for the rapid, low-cost and accurate detection and quantification of IL-6 using voltammetry technique. Graphite screen-printed electrodes modified with carbonaceous nanomaterial were used to fabricate electrochemical sensors exploiting carbodiimidemediated amide coupling reaction to immobilize the primary antibody; two selective capture bioreceptors, identified as mAb-IL-6 clone-5 and clone-7, were tested. The immunosensors were able to detect IL-6 levels with a limit of detection (LOD) of 4.4 and 2.1 pg/mL, the limit of quantification of 14.7 and 7.2 pg/mL and linear range of 17-85 and 16-205 pg/mL for clones-5 and 7, respectively. The immunosensors have shown better performances concerning commercial spectrophotometric ELISA kit (LOD of 20 pg/mL and LR of 25-200 pg/mL), associated with a reduced detection time (30 min). The developed IL-6 immunosensor with mAb-IL-6 clone-5 was also tested in human serum and blood sample showing good sensitivity, selectivity and reproducibility (RSD% of 6 %), without additional treatments, but only a dilution in a buffer solution (1:100 v/v). The successful application in a real matrix sample paves the way to the feasible application in other bio-fluids as simple point-of-care devices, representing a rapid screening test for IL-6 level determination.