Effect of hydrophobic modification of block copolymers on the self-assembly, drug encapsulation and release behavior

Abstract

In recent years, block copolymers together with their structure-property relationship in administrable drug delivery have attracted much concern. Three block copolymers BP123, BPF123 and H123 with the same PEO and PPO segments but different hydrophobic modification groups were synthesized. Commercial Pluronic block copolymers P123 was chosen for contrast. The effects of hydrophobic modification on the self-assembling behavior of the four copolymers were investigated via surface tension, transmission electron microscopy, steady state fluorescence and dynamic light scattering. With the enhancement of hydrophobicity, P123, BP123, BPF123 formed micelles and gradually decreased in critical aggregation concentrations (CAC) and size, while H123 formed vesicles. The dissolution and in vitro release capacities of the aggregates for the hydrophobic drug simvastatin were also evaluated. The stronger the hydrophobicity of copolymers, the stronger the drug solubilization ability for hydrophobic drug (H123 > BPF123 > BP123 > P123). Due to the enhancement of hydrophobicity, the tightly packed micelles formed by BP123 and BPF123, the drug release was slower. H123 had the highest solubility due to the closed bilayer vesicle structure and the interaction of hydrophobic groups with the drug, providing the slowest release rate. This study revealed that hydrophobic modification had a great impact on the self-assembly behavior of copolymers, modified copolymers can be applicable to sustained release drug carriers.