Functionalized graphitic carbon nitride as an efficient electro-analytical platform for the label-free electrochemical sensing of interleukin-8 in saliva samples

Abstract

A correlation between the emerging high case fatality rate of head and neck cancer and its propensity to migrate metastatically to other parts of the body makes it a significant global danger. It raises the demand for low-level detection, which is useful for early-stage diagnostics. Graphitic carbon nitride (g-C₃N₄) has recently garnered considerable attention as a promising nanomaterials for biosensor due to its exceptional redox behavior, electrochemical activity, and abundance of electroactive sites. The current study presents research outcomes regarding the development of an ultra-sensitive platform for detecting interleukin-8 (IL8), a cytokine associated with oral cancer. This investigation involves fabricating the platform using 3-aminopropyl trimethoxysilane (APTES)-functionalized g-C₃N₄ and assessing its efficacy in both laboratory-made and real samples. The process of g-C₃N₄ synthesis involved the thermal pyrolysis of urea without any add-on material. Moreover, the APTES@g-C₃N₄ nanomaterial was subjected to electrophoretic deposition onto an ITO-coated glass electrode. The fabricated APTES@g-C₃N₄/ITO electrode was covalently immobilized by the EDC and NHS chemical reaction in conjunction with anti-interleukin-8 (anti-IL8) antibodies. Before using these sensors for interleukin-8 (IL8) sensing, the anti-IL8/APTES@g-C₃N₄/ITO electrode was treated with bovine serum albumin (BSA) molecules utilized to obstruct non-targeted areas. Such a fabricated BSA/anti-IL8/APTES@g-C₃N₄/ITO electrochemical immunosensing bioelectrode was characterized by various analytical, morphological, and electrochemical techniques to confirm the stepwise fabrication of the sensor. BSA/anti-IL8/APTES@g-C₃N₄/ITO demonstrates a noticeable DPV based electrochemical response as a function of IL8 in the concentration ranging from 500 fg mL^-1 to 160 ng mL^-1. This BSA/anti-IL8/APTES@g-C₃N₄/ITO also exhibits a lower limit of detection (LOD) of 0.04 ng mL^-1, a sensitivity of 0.015 mA log₁₀ [ng mL^-1] cm^-2, and stability for up to 10 weeks. The biosensor demonstrates excellent performance in analyzing real samples, indicating its practical utility. This efficacy can be attributed to the abundance of electroactive sites, confined electronic structures, and strong interactions among the active g-C₃N₄ matrix, anti-IL8 molecules, and IL8 molecules. Our findings are essential for advancing early and point-of-care diagnostics, where quick turnaround times and great sensitivity are critical.