Portable metal-organic frameworks paper electrode with confinement-enhanced sensitivity for tetracycline antibiotics detection: Unleashing the power of spatial confinement

Integrated PNCE enables dual-interface confinement and electrochemical sensing. • ZIF-8 confined growth regulates transport and enhances selective adsorption. • Sensitive TC detection with low LOD (0.22 ng mL −1 ) and high enrichment (>85%) in chicken samples. Nanochannel-based electrochemical sensors show great promise for food analysis, yet small-molecule detection remains challenging due to insufficient molecular recognition and limited interface utilization. Herein, we report a portable paper-based nanochannel electrode (PNCE) integrated with selective adsorption elements, in which nanoporous gold layers were modified on both sides of the nanochannels, and its application in small-molecule analysis was explored. ZIF-8 was controllably grown across the outer surfaces and internal fibrous pathways through counter-diffusion, narrowing the local transport pathways and restricting ion and probe transport. Combined with the strong adsorption capability of ZIF-8, the resulting ZIF-8/PNCE system directly captured target small molecules and suppressed the diffusion of electrochemical probes, thereby enabling sensitive small-molecule detection without requiring additional labeling or biological recognition elements. Based on the cooperative contribution of outer-surface interaction and inner-channel confinement, the ZIF-8/PNCE system achieved preferential adsorption and sensitive class-level detection of tetracycline-class antibiotics (TCs), with TC selected as a representative model analyte and a detection limit of 0.22 ng mL −1 , comparable to or even surpassing many sensing systems that rely on biological recognition probes. Moreover, electrostatic potential and binding-energy simulations further confirmed the strong interaction between TC and ZIF-8. Reliable recoveries (94.16–115.6%) in real chicken samples demonstrated the practical applicability of the platform. This work establishes a dual-interface confinement-regulated electrochemical sensing strategy for portable and label-free small-molecule analysis. Download: Download high-res image (168KB) Download: Download full-size image