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In this study, we demonstrate the role of M cells in uptake of poly(D-L-lactic-co-glycolic acid) (PLGA) microspheres and transport into rabbit Peyer's patches. Microspheres 1 to 10 microns in diameter composed of 50:50 lactic acid:glycolic acid were instilled into intestinal segments containing jejunal or ileal Peyer's patches, and uptake by M cells was examined by electron microscopy. PLGA microspheres visualized as electron-lucent, spherical particles were taken up by M cells by pseudopod-like extensions of the M cell apical membrane and translocated to the pocket region containing mononuclear leukocytes within 60 min. These results indicate that PLGA microspheres can be directed to M cell apical surfaces for delivery to immunocompetent cells in gut-associated lymphoid tissues.

The main objective of this study was to prepare pellets in a Roto-processor using the powder-layering process onto inert nonpareils and to evaluate the applicability of the Roto-processor setup for film coating. Nonpareils were loaded with phenylpropanolamine hydrochloride and $lm coated with ethyl cellulose polymeric dispersion (Surelease@). The drug loading was analyzed to test the eficiency of powder layering. The effect of polymer level on the drug release from the pellets and the pore size distribution in the membrane were studied. The yields for powder layering were greater than 90%. The dissolution studies on the Blm-coated pellets showed sustained release over a 10-hr period. The time required for 50% of drug release increased and the mean pore diameter decreased with an increase in polymer coating.

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