Evaluation of antioxidant activity of caffeic acid phenethyl ester loaded block copolymer micelles

Caffeic acid phenethyl ester (CAPE), a hydrophobic constituent of poplar propolis of valuable biological activity, was immobilized in poly(ethylene oxide)-b-poly(epsilon-caprolactone)-b-poly(ethylene oxide) (PEO-b-PCL-b-PEO) copolymer micelles to improve its solubility in water. CAPE was loaded in the micelles by dialysis, achieving ca. 50% encapsulation efficiency. The drug loaded micelles were characterized with a mean diameter of 39 nm, narrow size distribution and slightly positive zeta-potential (approximately 2 mV). The in vitro release profile showed an improved dissolution behavior of micellar CAPE than pure CAPE. In vitro studies on human hepatoma HepG2 and neuronal SH-SY5Y cells demonstrated that the empty PEO-b-PCL-b-PEO micelles were not cytotoxic, whereas the drug loaded micelles exerted cytotoxic effects proportional to CAPE content. The protective activity of pure and micellar CAPE was investigated in a model of H2O2 induced oxidative damage in HepG2 and SH-SY5Y cells. In both cell types, micellar CAPE exhibited better protective activity against the oxidative damage than pure CAPE at very low concentrations (0.1 mu g/mL), which is far from the cytotoxic concentration of CAPE-loaded micelles (71 mu g/mL). Consequently, the developed micellar formulation has an improved activity against oxidative damage in hepatic and neuronal cells as comparing to pure CAPE.