AIM:To prepare the chitosan-pmEpo nanoparticles and tostudy their ability for transcellular and paracellular transportacross intestinal epithelia by oral administration.METHODS:ICR mice were fed with recombinant plasmidAAV-tetO-CMV-mEpo (containing mEpo gene) or pCMVβ(containing LacZ gene),whether it was wrapped by chitosanor no.Its size and shape were observed by transmission electronmicroscopy.Agarose gel electrophoresis was used to assessthe efficiency of encapsulation and stability against nucleasedigestion.Before and after oral treatmant,blood sampleswere collected by retro-orbital puncture,and hematocritswere used to show the physiological effect of mEpo.RESULTS:Chitosan was able to successfully wrap the plasmidand to protect it from DNase degradation.Transmissionelectron microscopy showed that freshly prepared particleswere approximately 70-150 nm in size and fairly spherical.Three days after fed the chitosan-pCMVβ complex was fed,the mice were killed and most of the stomach and 30% ofthe small intestine were stained.Hematocrit was not modifiedin naive and ‘naked’ mEpo-fed mice,a rapid increase ofhematocrit was observed during the first 4 days of treatmentin chitosan-mEpo-fed animals,reaching 60.9±1.2% (P<0.01),and sustained for a week.The second feed (6 days after thefirst feed) was still able to promote a second hematocritincrease in chitosan-mEpo-fed animals,reaching 65.9±1.4%(P<0.01),while the second hematocrit increase did not appearin the ‘naked’ mEpo-second-fed mice.CONCLUSION:Oral chitosan-DNA nanoparticles canefficiently deliver genes to enterocytes,and may be used asa useful tool for gene transfer. AIM: To prepare the chitosan-pmEpo nanoparticles and tostudy their ability for transcellular and paracellular transportacross intestinal epithelia by oral administration. METHODS: ICR mice were fed with recombinant plasmid AAV-tetO-CMV-mEpo (containing mEpo gene) or pCMVβ ), it was wrapped by chitosanor no. Its size and shape were observed by transmission electron microscopy. Agarose gel electrophoresis was used to assessthe efficiency of encapsulation and stability against nucleasedigestion. Before and after oral treatmant, blood samples were collected by retro-orbital puncture, and hematocritswere used to show the physiological effect of mEpo.RESULTS: Chitosan was able to successfully wrap the plasmid and to protect it from DNase degradation. Transmission electron microscopy showed that freshly prepared particles were approximately 70-150 nm in size and fairly spherical. Th days after fed the chitosan-pCMVβ complex was fed, the mice were killed and most of the stomach a nd 30% of the small intestine were stained. Hematocrit was not modified in naive and ’naked’ mEpo-fed mice, a rapid increase of hematocrit was observed during the first 4 days of treatment in chitosan-mEpo-fed animals, reaching 60.9 ± 1.2% (P <0.01), and sustained for a week. The second feed (6 days after the first feed) was still able to promote a second hematocritincrease in chitosan-mEpo-fed animals, reaching 65.9 ± 1.4% (P <0.01) hematocrit increase did not appear in the ’naked’ mEpo-second-fed mice. CONCLUSION: Oral chitosan-DNA nanoparticles canefficiently deliver genes to enterocytes, and may be used as a useful tool for gene transfer.