Nanoparticles consisting of a cross-linked cationic polymer network were prepared using Pluronic F127 and poly(ethylenimine) (PEI) and suggested as a drug delivery system for the anticancer drug Paclitaxel (PTX). In order to further improve the targeting capability of nanoparticles, folic acid (folate) was conjugated to the surface of nanoparticles. The characteristics were determined by various methods such as FT-IR for drug state in nanoparticles and DLS and TEM for particle size and morphology. The results found that the drug-loading content was increased when folate was connected to the surface of these nanoparticles. In vitro release experiments indicated that the PTX-loaded nanoparticles showed sustained release profiles compared to PTX solution, especially when nanoparticles were modified by folate. The cytotoxicity of PTX-loaded nanoparticles against cancer cell in vitro was remarkably higher than that of free drug and was better when folate, whose receptor was highly expressed in various tumors, was conjugated to the surface of these nanoparticles. The data demonstrated that this carrier-based approach to delivery of cytotoxic drugs may enhance tumor specificity and significantly reduce side effects related to systemic toxicity usually observed during cancer chemotherapy. (C) 2010 Elsevier Inc. All rights reserved.