Visual Detection of H₂O₂ in Serum Based on Covalent G-Quadruplex Hemin

This work presents a G-quadruplex heme chloride DNA peroxidase biosensing system. To address the instability and strong background signal issues in visual H₂O₂ detection, a G-quadruplex was prepared by using four trimeric DNA strands, and hemin was attached via covalent binding. The covalent binding significantly improved the color rendering effect and reduced the background signal. Four types of single-stranded DNA were compared for catalytic activity, with (GGGA)3 showing the best performance. The system was successfully applied to detect H₂O₂ in human serum, reaching a minimum detection concentration at the nanomolar level. This study provides valuable data for selecting single-stranded DNA in G-quadruplex preparation and holds potential for visual H₂O₂ detection in biomedicine and various industrial fields.