INS and diabetes mellitus: In order to observe the GR-NPs in vivo, diabetes rats were orally delivered by fluorescein isothiocyanate labeled insulin (FITC-INS)/GOx loaded GR-NPs (50 IU/kg), then were observed under living imaging systems (IVIS Lumina II, Caliper Life Science, the USA) with the following time at 1 h, 2 h, 3 h, 4 h.