Self-reduced Pd nanoparticles on NiMn-LDHs with superior catalytic activity for signal amplification in electrochemical aptasensing of Mycobacterium tuberculosis ESAT-6 antigen

Non-sputum-based diagnostic tests for tuberculosis (TB) are critical to global TB control. Herein, we developed an electrochemical aptasensor for detecting the ESAT-6 antigen of Mycobacterium tuberculosis (MTB) in human serum, using NiMn-layered double hydroxides@palladium nanoparticles (NiMn-LDHs@PdNPs) as a high-performance signal enhancer. NiMn-LDHs@PdNPs were synthesized via spontaneous in situ reduction, which requires no toxic reagents or complex equipment. This design not only addresses the limitations of insufficient active sites and slow electron transfer in layered double hydroxides (LDHs) but also mitigates the agglomeration tendency of palladium (Pd) nanoparticles, thereby enabling synergistic peroxidase-like activity and, importantly, relative spatial decoupling of recognition sites from catalytic sites. Functionalization with aptamers targeting the MTB ESAT-6 antigen did not significantly impair its catalytic activity. Employing a classic sandwich configuration, the aptasensor exhibited a wide linear detection range of 75 pg/mL to 10 ng/mL with a low limit of detection (LOD) of 0.629 pg/mL, alongside excellent specificity, stability, and reproducibility. In clinical validation, it successfully distinguished 14 TB patients from 14 healthy donors with 100% accuracy and outperformed enzyme-linked immunosorbent assay (ELISA). This work provides a high-performance non-sputum-based tool for TB diagnosis and advances the design of nanozyme-based biosensors.