A homogeneous electrochemical aptasensor based on Pd@rGO and targeted methylene blue enrichment for sensitive detection of dibutyl phthalate

Efficient detection of phthalate esters (PAEs) is of great significance for assessing ecological environment and food safety. This work developed an electrochemical aptasensor based on a Pd@rGO/GCE sensing electrode, which utilizes target-induced conformational changes of G-quadruplex (G4) to regulate the accumulation of methylene blue (MB) on the electrode surface for homogeneous and efficient detection of dibutyl phthalate (DBP). Benefiting from the target-triggered competitive release of truncated strands (H1 and H2) in homogeneous solution, the efficient adsorption of MB by G4, and the excellent conductivity and electrochemical activity of Pd@rGO/GCE, the constructed biosensor achieved a detection limit down to 9.3 × 10⁻⁷ mg/mL. It also exhibited high specificity toward PAEs, effectively distinguishing interfering substances, and demonstrated remarkable reproducibility and stability. Material characterization (SEM, EDS, XRD and XPS) confirmed the formation and uniform distribution of Pd NPs on the rGO surface, ensuring high electrochemical activity. More importantly, the homogeneous solution-based detection is free from interference related to electrode surface materials, charge, or steric hindrance, making the detection more accurate and efficient. Furthermore, experimental investigations demonstrated the structural advantages and signal amplification capability of the truncated strands. Overall, this work provides a novel, efficient, and reliable method for PAEs detection, offering valuable insights for applications in environmental monitoring and food safety.