Release kinetics of hydrophobic and hydrophilic model drugs from pluronic F127/poly(lactic acid) nanoparticles

Abstract

Poly(lactic acid) (PLA) was successfully grafted to both ends of Pluronic F127 block copolymers (PEO–PPO–PEO) to obtain amphiphilic PLA–F127–PLA block copolymers. The block composition and structure of PLA–F127–PLA block copolymers were studied by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetric (DSC) and wide angle X-ray diffraction (WXRD) techniques. Data from DSC and WXRD measurements indicated that T g and T m of PLA blocks in PLA–F127–PLA block polymers are lower than those of PLA homopolymer. Furthermore, T m and crystallinity of PLA blocks decrease with decreasing PLA block length in PLA–F127–PLA block copolymers. The release behaviors of both hydrophobic 9-(methylaminomethyl)anthracene (MAMA) and hydrophilic procaine hydrochloride (PrHy) model drugs from PLA–F127–PLA nanoparticles with vesicular structure in PBS solution at 37 °C were examined by UV spectroscopy. The release kinetics of both MAMA and PrHy model drugs from PLA–F127–PLA nanoparticles exhibit burst release characteristics, which are believed to be controlled by concentration gradient resulting from the slow hydrolytic degradation of PLA segments.