Biographene-Based Nanozyme for Rapid Colorimetric Detection of Oxytetracycline via Peroxidase-Mimicking Activity

Advancing sustainable graphene production is crucial to unlocking its potential in biomedicine and environmental technology. Although graphene offers exceptional electrical, mechanical, and surface properties, its large-scale utilisation is hindered by conventional synthesis methods such as chemical vapour deposition (CVD), which are costly, energy-intensive, and environmentally harmful. In this study, we report an eco-friendly, scalable, and cost-effective protein-assisted approach for exfoliating graphite into high-quality graphene in aqueous media using bovine serum albumin (BSA) as a biodegradable dispersant. BSA not only enables efficient exfoliation but also introduces abundant protein-derived functional groups, improving aqueous stability (zeta potential: -28.8 mV at pH 8) and ensuring long-term colloidal dispersion. These moieties enhance dispersibility while imparting intrinsic peroxidase-like activity under acidic conditions. Utilizing this nanozymatic activity, we developed a colorimetric sensing platform for rapid and sensitive detection of oxytetracycline (OTC). The assay is based on the inhibition of biographene-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of hydrogen peroxide, where OTC suppresses radical-mediated oxidation. The sensor exhibited high selectivity with a low detection limit of 2.66 µM and showed good biocompatibility, underscoring its biomedical potential. The green strategy enables sustainable production of functional graphene, positioning biographene as a promising material for diverse sensing applications.