Surface-modified titanium carbide MXene as an effective platform for the immobilization of toluidine blue and H2O2 biomarker detection in biological samples

Abstract

The development of reliable and cost-effective electrochemical sensors for hydrogen peroxide (H₂O₂) monitoring is crucial in biomedical diagnostics, especially in early disease diagnosis. Herein, we prudently synthesized an acid-functionalized COOH–Ti₃C₂T_x MXene, onto which a toluidine blue (TB) redox mediator was covalently immobilized and employed for the distinctive determination of H₂O₂. The synthesized COOH–Ti₃C₂T_x MXene is coated over a glassy carbon electrode (GCE), followed by the covalent immobilization of the electroactive TB dye through the N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) coupling reaction. This in turn results in the firm anchoring of the TB dye by establishing a stable amide linkage between the –COOH group of COOH–Ti₃C₂T_x and the free –NH₂ group of TB. Thus, the obtained TB/COOH–Ti₃C₂T_x/GCE sensor demonstrates an excellent electrocatalytic response for H₂O₂ determination over a broad linear range of 5 μM to 100 μM and 100 μM to 1.1 mM with a high sensitivity of 0.61 μA μM⁻¹ cm⁻² and a low detection limit of 1.5 μM. Notably, the fabricated electrode demonstrated exceptional stability and reproducibility as well as high selectivity and sensitivity in the detection of H₂O₂. Furthermore, the developed sensor showed very good recovery towards the detection of H₂O₂ in milk and serum samples. The attained analytical performance is attributed to the improved electrical wiring between the TB mediator and the conductive MXene platform.