Dual-functional PCN-242 (Fe2Co) MOF for sensitive bacterial endotoxin detection†

Abstract

Endotoxin detection is paramount for monitoring bacterial contamination in food, pharmaceuticals, and clinical diagnostics. The limulus amebocyte lysate (LAL) test, which relies on horseshoe crab blood, has long been the gold standard for endotoxin detection. However, the widespread adoption of this method is constrained by ethical concerns and the high costs associated with harvesting endangered species. Although nanozyme-based colorimetric methods present a more cost-effective and straightforward alternative, their application is limited by suboptimal selectivity and sensitivity. In this study, we report the synthesis and rigorous characterization of the bimetallic PCN-242 (Fe₂Co) metal–organic framework (MOF), synthesized using 2-amino terephthalic acid and a pre-synthesized [Fe₂Co(μ₃-O)(CH₃COO)₆] cluster. Steady-state kinetic analyses revealed that PCN-242 (Fe₂Co) MOF exhibits a significantly higher affinity for hydrogen peroxide (H₂O₂) compared to horseradish peroxidase (HRP) and other iron-based MOFs. The development of a PCN-242 (Fe₂Co)-based colorimetric sensor demonstrated a low limit of detection (LOD) of 1.36 μg mL⁻¹ for endotoxins, with excellent selectivity and reproducibility, thereby enabling effective detection of bacterial endotoxins. Recognizing the potential of the PCN-242 (Fe₂Co) MOF beyond endotoxin detection, we explored its utility in glucose biosensing. Moreover, incorporating glucose oxidase (GOx) into the PCN-242 (Fe₂Co) MOF framework further enhanced its peroxidase-like catalytic activity. This integration enabled sensitive glucose detection, achieving LODs of 4.24 μM for glucose and 2.2 μM for H₂O₂ within a linear range of 1 to 150 μM. The dual functionality of PCN-242 (Fe₂Co) MOF as a peroxidase mimic and biosensor platform highlights its potential for advanced catalytic and diagnostic applications, offering a versatile and ethical alternative to conventional methods.