Nanogel composed of rhodamine B isothiocyanate-labeled cinnamoyl polymeric β cyclodextrin and cinnamoyl Pluronic F127 was prepared by taking advantage of their self-assembling property in aqueous phase. The in vivo lifetime of the nanogel in the blood circulation system of hairless mouse was determined by fluorescence imaging method using rhodamine B isothiocyanate as a fluorescence probe, and it was more than 192 h. The in vivo clearance of doxorubicin loaded in the nanogel was observed by the same fluorescence imaging method. Doxorubicin loaded in the nanogel was cleared from the blood circulation system more slowly than free drug, indicating that the in vivo lifetime of the anti-cancer drug was prolonged by the nanogel. The fluorescence of doxorubicin was detected from the mouse even 200 h after the doxorubicin-loaded nanogel was intravenously injected into a mouse. According to the histological study of tumor tissue, the in vivo tumor growth-inhibiting efficacy of doxorubicin loaded in the nanogel was higher than that of free drug, possibly because of its longer in vivo lifetime.
Keywords: Rhodamine B isothiocyanate; cinnamoyl Pluronic F127; cinnamoyl polymeric β cyclodextrin; doxorubicin; in vivo anti-cancer efficacy; in vivo clearance; in vivo lifetime; nanogel.