THE EFFECT OF SIZE ON UPTAKE OF ORALLY-ADMINISTERED LATEX MICROPARTICLES IN THE SMALL-INTESTINE AND TRANSPORT TO MESENTERIC LYMPH-NODES

Purpose, The present study examines the relationship between size and particle transit across the mucosal barrier of the gastrointestinal tr act to other sites of the body. The extent of particle uptake with inc reasing size, the tissue distribution and cut-off points for 2-20 mu m particles is investigated. Methods, An established fluorescent latex particle-young adult rat model is used and particle numbers in small i ntestine and mesenteric lymph nodes, 0.5 h post administration, counte d by fluorescence microscopy in bulk tissue specimens and cryosections . Results, Bulk tissue analysis provides evidence for the presence of particles of all sizes in the Peyer's patch regions, but only for 2 mu m particles in the nodal tissues. Microscopy establishes uptake of bo th 2 and 6 mu m particles in most intestinal and nodal tissue sites an d compartments. By contrast, uptake of the larger particles is much re duced. Conclusions, Although more of the smaller (2 mu m) particles ar e taken up, particularly by epithelial tissues, the 6 mu m size appear s more efficient in terms of volume translocated to lymph nodes. This could have implications in the therapeutic use of particles for drug a nd vaccine delivery and for radiation safety.