Lemongrass (Cymbopogon citratus) peroxidase-modified screen-printed graphene electrodes for electrochemical sensing of hydrogen peroxide

The electrochemical sensing of hydrogen peroxide (H₂O₂) using biosensors, particularly those that rely on the catalytic reduction facilitated by natural proteins such as peroxidases (PODs), has emerged as an effective alternative for H₂O₂ detection. This study represents the first investigation of lemongrass peroxidase (LGP) in electrochemical sensors and focuses on the electrochemical sensing of H₂O₂ using LGP and screen-printed graphene electrodes (SPGE). LGP was extracted and partially purified using aqueous two-phase partitioning with 14% PEG and 10% (NH₄)₂SO₄, followed by ultrafiltration with 30 kDa Amicon filters, yielding a specific activity of 124.37 U/mg in the final extract. Biochemical characterization revealed that LGP exhibits optimal pH stability between 4.0 and 6.0, and thermal stability studies showed that 80% of enzymatic activity is retained between 40 °C and 66 °C. Additionally, the electrochemical behavior of LGP in H₂O₂ was SPGEs using cyclic voltammetry (CV). The LGP/SPGE system improved the reversibility of the redox process for K₃[Fe(CN)₆], reduced H₂O₂ at low potentials (0.43 V vs. Ag/AgCl), displayed linear response in the evaluated range (0.5–4 mM), and exhibited quasi-reversible behavior. These results indicate that LGP shows high biotechnological potential for H₂O₂ biosensors due to its stability, linear H₂O₂ response, and enhanced reduction capabilities.