Clonazepam release from core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol)/poly(epsilon-caprolactone) triblock copolymers

The triblock copolymer based on poly(epsilon-caprolactone) (PCL) as hydroph obic part acid poly(ethylene glycol) (PEG) as hydrophilic one was synthesiz ed and characterized. Core-shell type nanoparticles of poly(epsilon-caprola ctone)! poly(ethylene glycol)/poly(epsilon-caprolactone) (CEC) block copoly mer were prepared by a dialysis technique. According to the amphiphilic cha racters, CEC block copolymer can self-associate at certain concentration an d their critical association concentration (CAC) was determined by fluoresc ence probe technique. CAC value of the CEC-2 block copolymer was evaluated as 0.0030 g/l. CAC values of CEC block copolymer decreased with the increas e of PCL chain length, i.e. the shorter. the PCL chain length, the higher t he CAC values. From the observation of transmission electron microscopy (TE M), the morphologies of CEC-2 core-shell type nanoparticles were spherical shapes. Particle size of CEC-2 nanoparticles was 32.3 +/- 17.3 nm as a mono modal and narrow distribution. Particle size, drug loading, and drug releas e rate of CEC-2 nanoparticles were changed by the initial solvents and the molecular weight of CEC. The degradation behavior of CEC-2 nanoparticles wa s observed by H-1 NMR spectroscopy. It was suggested that clonazepam (CNZ) release kinetics were dominantly governed by diffusion mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.