Fig. 4.

The in vitro cumulative insulin release from GR-NPs in PBS buffer with different glucose concentrations (0 mg/dL, 100 mg/dL and 400 mg/dL) (a); pulsatile release profile of GR-NPs presents the rate of insulin release as a function of glucose concentration (100 mg/dL and 400 mg/dL) (b); phosphorescence lifetime of the GR-NPs incubated with different glucose concentration solutions (0 mg/dL, 100 mg/dL and 400 mg/dL) containing an oxygen concentration molecule probe (c). A significantly higher (**P < 0.01) efficacy of GR-NPs was observed at various time points in 400 mg/dL compared with in PBS buffer