Endomicroscopic fluorescence lifetime imaging enables molecular detection and targeted sampling in the distal human lung
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Purpose
Accurate molecular characterisation of infection and inflammation within the distal human lung remains challenging, particularly in critically ill patients, due to limited access to the alveolar space and delayed diagnostic workflows. Molecular imaging approaches capable of real-time detection and targeted sampling could substantially improve diagnostic precision and the future translational development of molecular imaging probes and therapeutics.
Methods
In a preclinical setting, we evaluated a clinic-ready endomicroscopic fluorescence lifetime imaging microscopy (eFLIM) platform combined with molecularly targeted SmartProbes for in situ detection of bacteria and activated neutrophils in the distal human lung. A multifunctional 1.9-mm diameter imaging and sampling catheter (Eyes on Target; EoT) enabled real-time fluorescence intensity and lifetime imaging alongside directed alveolar microlavage via a 1.2-mm working channel. Fluorescence intensity and lifetime signatures of Gram-negative bacteria, Gram-positive bacteria, and activated neutrophils were characterised using three wash-free SmartProbes: NBD-PMX, Merocy-Van, and a neutrophil activation probe (NAP). Imaging and sampling performance were assessed in ventilated ex vivo human lungs.
Results
EoT reliably navigated to alveolar regions across all lung lobes in both phantom and ventilated human lung models. eFLIM distinguished alveolar microanatomy and enabled probe-specific molecular detection within the distal lung. Increased NBD-PMX signal was detected in Escherichia coli –instilled lobes, while Merocy-Van lifetime signatures selectively identified Staphylococcus aureus –instilled regions. Activated neutrophils were detected throughout lung tissue following NAP administration. Directed alveolar microlavage enabled recovery of cellular material and bacterial DNA from imaged regions for downstream analysis.
Conclusion
eFLIM using EoT combined with molecular SmartProbes enables real-time molecular imaging and targeted sampling within the distal human lung. This platform provides a translatable approach for evaluating infection and inflammation at the alveolar level and supports the clinical development of molecular imaging probes for pulmonary disease.
