In vivo residence duration of human growth hormone loaded in nanogels comprising cinnamoyl alginate, cinnamoyl Pluronic F127 and cinnamoyl poly(ethylene glycol)

Cinnamoyl alginate, cinnamoyl Pluronic F127 and cinnamoyl poly(ethylene glycol) were self-assembled into nanogel in aqueous phase. The size of nanogel was 100 nm–200 nm on TEM photos. When 1 ml of human growth hormone (hGH) solution (5 mg/ml, pH3.0) was mixed with 4 ml of the nanogel suspension (37.5 mg/ml, pH3.0), 100% of hGH was loaded in the nanogels (corresponding to specific loading of 3.33% (w hGH/w nanogel)). In the in vivo pharmacokinetics study, the substantial blood level of hGH was maintained during the entire experiment period (two weeks) after one-time injection of hGH-loaded nanogel at 0.5 mg hGH/kg body weight, and the area under curve (AUC) obtained with the one-time injection of hGH-loaded nanogel was higher than AUC obtained with daily injections of free hGH at 0.05 mg hGH/kg for 7 days. In the in vivo pharmacodynamics study, the blood level of insulin-like growth factor (IGF-1) increased in 2 h and it was maintained during the entire experiment period (two weeks) after one-time injection of hGH-loaded nanogel at 0.5 mg hGH/kg body weight. The in vivo fluorescence images of mice injected with rhodamine B isothiocyanate-labelled nanogel suspension showed fluorescence intensity up to 96 h after intravenous injection, indicating that the in vivo residence time of the nanogel was greater than 96 h.

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