FIG. 2.

(A) Rolipram (Rm) loading into poly(lactide-co-glycolide)-graft-polyethylenimine (PgP) micelle nanoparticles by the solvent evaporation method. 100 μL containing various concentrations of Rm (0–2 mg/mL in ethanol) was added into PgP (1 mg/mL in water) solution, incubated to allow ethanol evaporation, and filtered to remove free Rm, and the concentration of loaded Rm measured by high-performance liquid chromatography (HPLC). The maximum water solubility of free Rm is indicated by dashed red line (0.2 mg/mL). (B) The long-term stability of Rm-PgP incubated at 37°C for 6 weeks. Each week, solutions containing Rm-PgP were sampled and filtered with 0.2 μm syringe filter to remove released precipitated Rm and then Rm amount was measured by HPLC. The % Rm remained was calculated as: % Rm remained at given time-point = (amount of Rm in PgP at given time-point)/ (amount of Rm in PgP at time 0) × 100.