Chitosan-thioglycolic acid conjugate microspheres: their use for oral delivery of rEPO

Chitosan-thioglycolic acid conjugates were synthesized and their characteristics, including the thiol group content and bioadhesive properties, were evaluated. Chitosan-thioglycolic acid conjugate microspheres (C-TGACMs), containing erythropoietin (rEPO) as a model drug, with or without an enteric coating were prepared, and the entrapment efficiency, the drug release behavior in vitro and the antianaemic effect of rEPO were investigated. It was found that the chitosan-thioglycolic acid conjugate with a 5.56% (w/w) thiol group content exhibited better bioadhesion. Also, the C-TGACMs, with or without an enteric coating, had a good spherical shape and release profiles consisted of a quick-release phase and a stable sustained-release phase. The entrapment efficiencies of C-TGACMs, with and without an enteric coating, were 84.3 and 85.7%, respectively. When rEPO loaded enteric-coated C-TGACMs were given orally to rats, they produced an excellent antianaemic effect, which was evaluated by the Smear and Sysmex methods.