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The development of injectable hydrogels for protein delivery is a major challenge. In this study, insulin/alpha-cyclodextrin (alpha-CyD) and gamma-CyD polypseudorotaxane (PPRX) hydrogels were prepared through inclusion complexation between high molecular weight poly(ethylene glycol) (PEG) and CyDs. The alpha-CyD and gamma-CyD PPRX hydrogels were formed by inserting one PEG chain in the alpha-CyD cavity and two PEG chains in the gamma-CyD cavity. Insulin/CyD PPRX hydrogel formation was based on physical crosslinking induced by self-assembling without chemical crosslinking reagent. The supramolecular structures of insulin/CyD PPRX hydrogels were confirmed with (1)H nuclear magnetic resonance ((1)H NMR), X-ray diffraction, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The in vitro release study showed that the release rate of insulin from the CyDs PPRX hydrogels decreased in the order of gamma-CyD PPRX hydrogel>alpha-CyD PPRX hydrogel. This decrease was controlled by the addition of CyDs to the medium. The serum insulin level after subcutaneous administration of gamma-CyD PPRX hydrogel to rats was significantly prolonged, accompanying with an increase in the area under serum concentration-time curve, which was clearly reflected in the prolonged hypoglycemic effect. In conclusion, these results suggest the potential use of gamma-CyD PPRX hydrogel as an injectable sustained release system for insulin.

Topical application of nuclear factor-kappaB (NF-kappaB) decoy appears to provide a novel therapeutic potency in the treatment of inflammation and atopic dermatitis. However, it is difficult to deliver NF-kappaB decoy oligonucleotides (ODN) into the skin by conventional methods based on passive diffusion because of its hydrophilicity and high molecular weight. In this study, we evaluated the in vitro transdermal delivery of fluorescein isothiocyanate (FITC)-NF-kappaB decoy ODN using a pulse depolarization (PDP) iontophoresis. In vitro iontophoretic experiments were performed on isolated C57BL/6 mice skin using a horizontal diffusion cell. The apparent flux values of FITC-NF-kappaB decoy ODN were enhanced with increasing the current density and NF-kappaB decoy ODN concentration by iontophoresis. Accumulation of FITC-NF-kappaB decoy ODN was observed at the epidermis and upper dermis by iontophoresis. In mouse model of skin inflammation, iontophoretic delivery of NF-kappaB decoy ODN significantly reduced the increase in ear thickness caused by phorbol ester as well as the protein and mRNA expression levels of tumor necrosis factor-alpha (TNF-alpha) in the mice ears. These results suggest that iontophoresis is a useful and promising enhancement technique for transdermal delivery of NF-kappaB decoy ODN.