Abstract
Introduction
Fluorescent markers are available for monitoring of dose and bioactivity of drugs in preclinical animal models. However, quantitative fluorescence imaging of the whole lung is complicated by poor tissue penetration of light.
Objectives
In this pre-clinical study optical imaging methods were developed to quantify the dose and the distribution of fluorescent markers in the ex vivo lungs of mice.
Methods
Fluorescent polystyrene beads (ex/em=680 nm/710 nm) were used as surrogate drug and applied to the lungs of mice via intratracheal instillation (IT) as well as via mechanically-ventilated (m-v) and nose-only (n-o) inhalation. Excised lungs were sectioned into individual lobes, compressed to 1 mm and 0.7 mm thickness and imaged with an in-vivo imaging system (IVIS). Alternatively, ex vivo lungs were dried, sliced into 1mm thick slices and slice-by-slice imaged with the IVIS.
Results and Discussion
From imaging of the compressed lung lobes and the dried lung slices an effective light attenuation coefficient of 8.8±1.9 cm-1 was determined, which is consistent with literature data. Dried lung slice imaging provided 3D-information on the pulmonary drug distribution. Analysis of the regional distribution of the fluorophore yielded a central-to-peripheral (C/P) drug ratio of 1.9±0.4 for IT and 1.2±0.3 and 1.3±0.2 for m-v and n-o inhalation, respectively. As expected, IT delivers the marker preferentially into the central region, while both types of inhalation result in a more uniform distribution throughout the lung.
Conclusions
Using optical fluorescence imaging the dose and 3D distribution of fluorescently labelled drugs can be assessed in ex vivo mouse lungs.
- © 2014 ERS