A series of ABA- and BAB-type nanoparticles based on PCL and PEG were synthesized and thoroughly investigated. The properties of obtained polymers and nanoparticles were characterized by means of Fourier- Transform Infrared (FT-IR), proton Nuclear Magnetic Resonance (H-1 NMR), Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). Critical micelle concentration (CMC), volume fraction, hydrophilicity to lipophilicity balance (HLB), particle size and zeta potential of nanoparticles were evaluated. The nanoparticle morphology of ABA and BAB triblock copolymers were characterized by transmission electron microscopy (TEM). Chitosan coated PEG-PCL-PEG (Cs/PECE) and PCL-PEG-PCL (Cs/PCEC) nanoparticles were prepared for the first time. Thermal properties along with Flory-Huggins theory were used to understand the interaction of chitosan shell and PCL or PEG blocks of triblock core. In vitro release profiles of all drug-loaded nanoparticles were studied and the release kinetic was calculated. Cytotoxicity of core-shell nanoparticles was investigated. Generally, the prepared nanoparticles are suitable systems for drug delivery and their architecture makes them good candidates for programmable release systems. (C) 2012 Elsevier Ltd. All rights reserved.