Deepa A. Rao, Brianna Cote, Michelle Stammet, Adel M. Al Fatease and Adam W.G. Alani Pages 120 - 125 ( 6 )
Background: Many different methods have been developed to incorporate hydrophobic compounds into polymeric micelles, including simple equilibrium (SE) and solvent casting (SC). Thus far, no studies have compared the SE and SC methods for drug loading and stability.
Methods: Resveratrol (RES), a model hydrophobic compound, loaded in various Pluronics® (F88, F98, F108, and F127) is used to determine the differences between SE and SC methods.
Results: Micelles prepared by SE method demonstrated RES loading in proportion to their respective CMC values with F127 having the lowest CMC and highest loading at Day 14 of 5.39±0.19 mg/mL, followed by F98 at 3.65±0.13 mg/mL, F108 at 3.29±0.06, and F88 at 2.35±0.05 mg/mL. Initial RES loading in SC method approaches 10 mg/mL in all the polymers, however, the micelles are unable to retain RES at this concentration for more than a few hours to a day. At the lower loading of 5 mg/mL a higher stability is seen in the Pluronic® micelles. In all micelles prepared by SC method, whether high or low loading, over a 14 day period the RES concentration in the micelles approached the equilibrium RES solubility.
Conclusion: Our results demonstrate that micelles prepared by SC result in meta-stable micelles when the amount of the compound loaded exceeds the equilibrium loading and the rate at which the compound in the micelles approaches equilibrium solubility is determined by the hydrophobicity of the compound and the hydrophile- lipophile balance (HLB) of the polymer.
Drug loading and retention, micelle stability, pluronics®, polymeric micelles, resveratrol, simple equilibrium method, solvent casting method.
Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, 2730 SW Moody Ave, CL5CP, Portland Oregon 97201-5042, USA.