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 biosensor due to its exceptional redox behavior, electrochemical activity, and abundance of electroactive sites. The current study presents research outcomes regarding developing 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. 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 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 fabricated BSA/anti-IL8/APTES@g-C3N4/ITO electrochemical immunosensing bioelectrode was characterized by various analytical, morphological, and electrochemical techniques to confirm stepwise fabrication of the sensor. The BSA/anti-IL8/APTES@g-C3N4/ITO demonstrates a noticeable DPV-based electrochemical response as a function of IL8 antigen in the concentration ranging from 500 fg mL-1 to 160 ng mL-1. Our BSA/anti-IL8/APTES@g-C3N4/ITO also exhibits a lower limit of detection (LOD) of 0.04 ng mL-1, 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, and IL8 molecules. Our findings are essential for advancing early and point-of-care diagnostics, where quick turnaround times and great sensitivity are critical.