1: J Control Release  2002 Oct 30;83(3):331 

Confocal imaging of rat lungs following intratracheal delivery of dry powders or
solutions of fluorescent probes.

Lombry C, Bosquillon C, Preat V, Vanbever R.

Universite catholique de Louvain, School of Pharmacy, Department of
Pharmaceutical Technology, Avenue E. Mounier, 73 UCL 73.20, 1200, Brussels,
Belgium

The overall pulmonary disposition of various fluorescent probes was viewed by
confocal imaging following intratracheal delivery in the rat in vivo. The green
fluorescent dyes, coumarin-6, a 350 Da lipophilic molecule; calcein, a 623 Da
hydrophilic molecule; or FITC-albumin, a 65000 Da hydrophilic molecule; were
insufflated as a dry powder or instilled as a solution in the lungs of rat in
vivo. Immediately, 2 or 24 h following delivery, the lungs were colored with
sulforhodamine and fixed by vascular perfusion. The lungs were then removed,
grossly sliced and examined by confocal laser scanning fluorescence microscopy.
Coumarin-6 diffused within minutes across the trachea, airways and alveolar
tissue but was also retained for hours in type II alveolar epithelial cells. The
diffusion of calcein across the tissue was fast as well, with no particular
affinity for specific cells. FITC-albumin slowly permeated the tissue. It
remained in the airspaces for hours and was intensively captured by alveolar
macrophages. Compared to the powder, the solution bypassed dissolution and
therefore shortened the lag time for diffusion and cellular capture. The
technique allowed to obtain an overview of the fate of fluorescent probes
locally in each region of the lungs and highlighted the strong dependence of the
localization behavior on physico-chemical properties of molecules as well as a
capture by particular cells of the pulmonary tissue.

PMID: 12387942 [PubMed - in process]