The quantitation of the absorption of microparticles into the intestinal lymph of Wistar rats

The absorption of polystyrene microparticles across the intestine of rats was examined as a preliminary assessment of the efficacy of particles as vaccine delivery systems. The superior mesenteric lymph ducts of groups (n = 5) of Wistar rats were cannulated and the lymph analysed by flow cytometry. This allowed direct quantification of the numbers of particles absorbed. The 0.15 and 1.0 μm particles were absorbed rapidly (after 5 min) in a temporally complex manner, with maximal absorption occurring 65 min after delivery, for both sizes of particles. Microparticles were absorbed in approximately equal numbers over 90 min (5.0 × 104 0.15 μm and 4.9 × 104 1.0 μm particles, respectively). The levels of particle absorption in the current study indicate that microparticulate delivery of vaccines may be a realistic possibility.