Electrochemical microfluidic sensor based on hBN-CeO₂@Cyt c hydrogel-modified SPCE for the detection of hydrogen peroxide

Hydrogen peroxide (H₂O₂) is widely added to dairy products for shelf life enhancement but is also a recognized adulterant. In this study, a novel nanomaterial H₂O₂ sensor was fabricated using a hexagonal boron nitride-cerium oxide nanocomposite and a redox protein cytochrome c-embedded hydrogel, referred to as the hBN-CeO₂@Cyt c hydrogel nanocomposite. The unique nanomaterial-redox protein-embedded hydrogel platform provides a large electroactive surface area; and a 3D porous microenvironment for enhanced interaction of Cyt c and hBN-CeO₂ and improved conductivity for enhancing electrochemical signals. The confirmation of hBN-CeO₂@Cyt c hydrogel formation was obtained using field-emission scanning electron microscopy (FE-SEM), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy. The electrochemical characterization of the hBN-CeO₂@Cyt c hydrogel/SPCE was performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) within a concentration range of 5–50 µM. The calculated limit of detection (LOD) was 1.70 µM, and the limit of quantification (LOQ) of 5.15 µM. Additionally, a customized microfluidic device was developed and integrated with hBN-CeO₂@Cyt c hydrogel/SPCE for continuous detection of H₂O₂. The redox couple (K₃Fe(CN)₆ and KCl) and H₂O₂ solution were transferred through the inlets of the microfluidic channel at a 10 µL/min flow rate. The DPV analysis conducted in the flow-type cell for H₂O₂ detection demonstrated the exceptional sensitivity of microfluidic electrochemical devices. The calculated LOD was 1.43 µM, while the LOQ was 4.34 µM, and the sensitivity was 0.9156 µA µM⁻¹ cm⁻². The sensor showed a good recovery rate (98.6 to 106%.) in raw milk, suggesting versatile applications in the food industry, especially in dairy products.