In this study, methotrexate (MTX)-encapsulated polymeric micelles using methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymer were prepared. The MTX-incorporated polymeric micelles of ChitoPEG copolymer has a particle size of around 50-100 nm. In 1H nuclear magnetic resonance (NMR) study, the specific peaks of MTX disappeared in heavy water (D 2 O) and only the specific peak of MPEG was observed, while all of the peaks were confirmed in dimethyl sulfoxide (DMSO). These results indicated that MTX was complexed with chitosan and then formed an ion complex inner-core of the polymeric micelle in an aqueous environment. The drug contents of the polymeric micelle were around 4~12% and the loading efficiency of MTX in the polymeric micelles was higher than 60% (w/w) for all of the formulations. The cytotoxicity of MTX and MTX-incorporated polymeric micelle against CT26 tumor cells was not significantly changed.

In this study, we prepared all-trans retinoic acid (ATRA)-encapsulated, surfactant-free, PLGA nanoparticles. The nanoparticles were formed by nanoprecipitation process, after which the solvent was removed by solvent evaporation or dialysis method. When a nanoparticle was prepared by the nanoprecipitation -solvent evaporation method, the nanoparticles were bigger than the nanoparticles of the nanoprecipitation -dialysis method, despite the higher although loading efficiency. Nanoparticles from the nanoprecipitation -dialysis method were smaller than 200 nm in diameter, while the loading efficiency was not significantly changed. Especially, nanoparticles prepared from DMAc, 1,4-dioxane, and DMF had a diameter of less than 100 nm. In the transmission electron microscopy (TEM) observations, all of the nanoparticles showed spherical shapes. The loading efficiency of ATRA was higher than 90 % (w/w) at all formulations with exception of THF. The drug content was increased with increasing drugfeeding amount while the loading efficiency was decreased. In the drug release study, an initial burst was observed for 2~6 days according to the variations of the formulation, after which the drug was continuously released over one month. Nanoparticles from the nanoprecipitation -dialysis method showed faster drug release than those from the nanoprecipitation -solvent evaporation method. The decreased drug release kinetics was observed at lower drug contents. In the tumor cell cytotoxicity test, ATRA-encapsulated, surfactant-free, PLGA nanoparticles exhibited similar cytotoxicity with that of ATRA itself.