A 3D porous PDA–PPY@ Au NPs nanocomposite-modified electrode enables picomolar electrochemical aptasensing of tetracycline

A three-dimensional (3D) porous PDA–PPY hydrogel with abundant anchoring sites, which facilitates Au NPs loading and accelerates electron transfer. • The Au NPs further improve conductivity, achieve dual signal amplification of the sensor. • The TC aptamer form a stable recognition interface with high affinity and specificity toward TC. • The proposed aptasensor exhibited an extra low detection limit of 2.7 pM toward TC. • the proposed aptasensor provides a robust and effective strategy for monitoring TC residues in real samples. Herein, a sensitive and reliable electrochemical aptasensor (BSA/Apt/PDA-PPY@Au NPs/GCE) was developed for the determination of tetracycline (TC). The sensing platform was built upon a green-synthesized PDA–PPY polymer hydrogel, which provides a three-dimensional porous architecture with abundant anchoring sites and favorable conductivity, enabling efficient loading of Au nanoparticles (Au NPs) and rapid interfacial electron transfer. The TC aptamer was then robustly immobilized onto the PDA–PPY@ Au NPs nanocomposite via directional Au–S bonding, forming a stable recognition interface with high affinity and specificity toward TC. Benefiting from the dual effects of the conductive PDA–PPY hydrogel and Au NPs, the proposed aptasensor exhibited high sensitivity with an extra low detection limit of 2.7 pM and a wide linear response range of 5 pM–1 μM. Moreover, it demonstrated excellent reproducibility, selectivity and good stability. Importantly, accurate determination of TC in real samples (milk and river water) was achieved with satisfactory recoveries and accuracy, highlighting the potential of this strategy for monitoring TC residues in food matrices and environmental waters. Download: Download high-res image (273KB) Download: Download full-size image