Aptamer-assisted MOF-on-MOF fluorescence–colorimetric dual-mode sensor for ultrasensitive detection of Acinetobacter baumannii in ICU environments

Aptamer-assisted MOF-on-MOF heterostructure for dual-mode AB sensing. • Orthogonal fluorescence/colorimetric self-validation in ICU matrices. • Boronic-acid/aptamer dual recognition for bacterial capture. • Ultrasensitive Acinetobacter baumannii detection with 5–12 CFU/mL LOD. • Accurate analysis of ICU swabs, hand wash, and ventilator condensate. Acinetobacter baumannii (AB) has become the most persistent “resident pathogen” in intensive care unit (ICU) environments due to its exceptional environmental survival capability, its ability to persist on dry inanimate surfaces, highly efficient adhesion through biofilm formation that resists disinfectants, and extensive multidrug resistance. Rapid and reliable monitoring of AB is essential for preventing healthcare-associated infections in ICUs. However, existing microbiological and molecular methods remain limited by slow turnaround times, high costs, and inadequate sensitivity for routine environmental screening. Here, we report a label-free, dual-mode fluorescence–colorimetric biosensing platform that integrates aptamer-mediated magnetic capture with a MOF-on-MOF heterostructure probe for ultrasensitive detection of AB in environmental samples from ICUs. The probe, ZrFe-MOF@Eu-MOF-BA, was constructed through the epitaxial growth of boronic acid-functionalized Eu-MOF shells on ZrFe-MOF. This heterostructure combines ligand-centered fluorescence, Fe 3+ /Fe 2+ -driven peroxidase-mimicking catalytic activity, and high-density boronic acid groups, enabling covalent affinity toward cis-diol-rich glycolipids on the AB surface. A robust magnetic sandwich complex is formed with aptamer-modified magnetic beads, allowing independent quantification through two orthogonal readouts. Across a broad range of 10–10 8  CFU/mL, the system achieved limits of detection of 5 and 8 CFU/mL in colorimetric mode (370 and 652 nm) and 12 CFU/mL in fluorescence mode. The sensor displayed good selectivity against the tested interfering bacteria and maintained high accuracy in spiked ICU environmental matrices, including hand-wash solutions, surface swabs, and ventilator condensates. Recoveries ranged from 92.3% to 108.0%, with RSDs < 4.5%. Strong agreement between the two detection channels further enhanced the reliability of the results. This work demonstrates a highly sensitive, low-cost, and easily deployable dual-mode biosensor suitable for rapid screening of AB contamination in clinical environments. The modular aptamer-based recognition mechanism also enables straightforward adaptation of the platform for the detection of other pathogenic microorganisms, offering broad potential for clinical surveillance and environmental biosensing applications Download: Download high-res image (86KB) Download: Download full-size image