Functionalized natural melanin nanoparticle mimics natural peroxidase for total antioxidant capacity determination

Natural peroxidase composed of protein and metallic cofactor suffers from deactivation in harsh environment. Learning from the natural structure of active site in peroxidase, in this work, natural melanin nanoparticles from cuttlefish were facilely functionalized with Fe3+ to construct peroxidase-like nanozyme, showing high stability and activity. In the presence of H2O2, Fe-melanin nanoparticles (Fe-NMPs) catalyzes the formation of·OH from H2O2, converting colorless 3,3,5,5-Tetramethylbenzidine (TMB) into blue oxidized TMB (ox-TMB). When the antioxidants were added into the system, ox-TMB will be reduced to colorless TMB, thus allowing the detection of total antioxidant capacity. The results show that the lowest detection limit of AA in Fe-NMPs is 12.61 μM and the detection range is 5–250 µm. The test results for AA were similar to the sample instructions for beverages and fruits, validating the feasibility of using Fe-NMPs for the actual total antioxidant capacity determination. This study provides a broader perspective for fabricating foodborne nanozyme for related applications.