Figure 2. In vitro release studies. A: Cumulative release of glial cell line–derived neurotrophic factor (GDNF; ng/mg microspheres) over 63 days from the GDNF/vitamin E (VitE)-loaded formulation (■) and from the GDNF/VitE/melatonin-loaded formulation (▲). Release media: PBS (pH 7.4) with 1% bovine serum albumin (BSA) and 0.02% Na Azide. B: Cumulative release of melatonin (µg/mg microspheres) over 63 days from the GDNF/VitE/melatonin-loaded formulation (●). Release media: PBS (pH 7.4). C: Schematic representation of the GDNF release rate (ng GDNF/mg microspheres/day) form the GDNF/VitE-loaded microsphere formulation and the GDNF/VitE/melatonin-loaded microsphere formulation during the 63 days. D: Schematic representation of the melatonin release rate (µg melatonin/mg microspheres/day) from the formulation of GDNF/VitE/melatonin-loaded MSs during the 63 days. Panel A, B, C sampling sizes (n=3); error bars are SEM.