Comparison of Poly(DL-Lactide-co-Glycolide) and Polystyrene Microsphere Targeting to Intestinal M Cells

The interaction of poly(DL-lactide-co-glycolide) (PLG) and polystyrene microspheres with the follicle-associated epithelium (FAE) of rabbit Peyer's patches was compared. Binding by PLG microspheres to the FAE was an order of magnitude lower than that of polystyrene microspheres of equivalent size (0.5-0.6 pm diameter). Although PLG microspheres are not selectively targeted to the M cell surface, as is the case with polystyrene microspheres, a high proportion of those that bind to M cells are transcytosed, resulting in the transepithelial delivery of 1.5x10(4) PLG microspheres/mm(2) FAE. This represents the first direct demonstration of transepithelial delivery of PLG microspheres by M cells, which is crucial to the potential use of such vehicles for the oral delivery of drugs and vaccines. As native PLG microspheres are not optimally targeted to the M cell surface, there is scope for the further improvement of their efficacy by surface modifications.