Ileal uptake of polyalkylcyanoacrylate nanocapsules in the rat

The ileal uptake of polyalkylcyanoacrylate nanocapsules (less than 300 nm i n diameter) has been investigated in the rat. Iodised oil (Lipiodol) was us ed as the tracer for X-ray microprobe analysis in scanning electron microsc opy. Lipiodol nanocapsules, or an emulsion of Lipiodol, were administered in the lumen of an isolated ileal loop of rat. Lipiodol nanocapsules improved the absorption of the tracer as indicated by increased concentrations of iodin e in the mesenteric blood (+27%, P < 0.01, compared with Lipiodol emulsion) . Intestinal biopsies were taken at different time points and the samples u nderwent cryofixation and freeze-drying. The nanocapsules were characterize d by their strong iodine emission, and electron microscopy of the biopsy sa mples revealed nanocapsules in the intraluminal mucus of the non-follicular epithelium, then in the intercellular spaces between enterocytes, and fina lly the nanocapsules were found within intravillus capillaries. However, na nocapsules were most abundant in the Peyer's patches, where the intestinal epithelium had been crossed by way of the specialized epithelial cells, des ignated membranous cells, or M cells, and their adjacent absorptive cells. These observations were confirmed quantitatively by measuring iodine concen trations in the various tissue compartments. Ten minutes after the intralum inal administration of Lipiodol nanocapsules, the emission of iodine peaked in the mucus (+77%, P < 0.01), in M cells (+366%, P < 0.001), in enterocyt es adjacent to M cells (+70%, P < 0.05) and in lymph vessels (+59%, P < 0.0 5). Polyalkylcyanoacrylate nanocapsules were able to pass through the ileal muc osa of the rat via a paracellular pathway in the non-follicular epithelium, and most predominantly, via M cells and adjacent enterocytes in Peyer's pa tches.