Pyrene Solubilization in Aqueous Micellar Solutions of Pluronic Block Copolymers

Micelles of Pluronic block copolymers have recently displayed a potential application as drug microcarriers.In the application,one of the key problems is effective solubilization of hydrophobic drugs in the micelles.However,solubilization regularities of hydrophobic materials in Pluronic micelles have not been fully studied.In this paper,the solubilization of pyrene(Py)in the aqueous micellar solutions of Pluronic block copolymers has been investigated by steady-state fluorescent spectra.The results showed that the PPO content in Pluronic molecule is a key factor to determine Py amount adsorbed in the micelles.The greater is the PPO content,the much favorably solubilizate Py in the micelles.In the molecules of Pluronic copolymers studied in this paper,PPO content orders as F108(2920)>P85(2300)>F68(1680)and thus the partition coefficients(KV)of Py between the micelles and water are 8.3×104(F108,35℃),5.7×104(P85,35℃）and 2.2×103(F68,40℃），respectively.Addition of KCl leads to formation of the larger micelle with less hydrated shell.This means formation of a larger micellar core available to accommodating hydrophobic Py molecules,which is in agreement with the experimental results that showed an enhancement in Py solubilization as addition of KCl.