Polysorbate 80 (Tween 80) has been widely used as an emulsifier with excellent effects in nanoparticles technology for biomedical applications. This work was thus triggered to synthesize poly(lactide)/Tween 80 copolymers with various copolymer blend ratio, which were synthesized by ring-opening polymerization and characterized by 1H NMR and TGA. Nanoparticles of poly(lactide)/Tween 80 copolymers were prepared by the dialysis method without surfactants/emulsifiers involved. Paclitaxel was chosen as a prototype anticancer drug due to its excellent therapeutic effects against a wide spectrum of cancers. The drug-loaded nanoparticles of poly(lactide)/Tween 80 copolymers were then characterized by various state-of-the-art techniques, including laser light scattering for particles size and size distribution, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) for surface morphology; laser Doppler anemometry for zeta potential; differential scanning calorimetry (DSC) for the physical status of the drug encapsulated in the polymeric matrix; X-ray photoelectron spectrometer (XPS) for surface chemistry; high performance liquid chromatography (HPLC) for drug encapsulation efficiency; and in vitro drug release kinetics. HT-29 cells and Glioma C6 cells were used as an in vitro model of the GI barrier for oral chemotherapy and a brain cancer model to evaluate in vitro cytotoxicity of the paclitaxel-loaded nanoparticles. The viability of C6 cells was decreased from 37.4 +/- 4.0% for poly(D,L-lactide-co-glycolic acid) (PLGA) nanoparticles to 17.8 +/- 4.2% for PLA-Tween 80-10 and 12.0 +/- 5.4% for PLA-Tween 80-20 copolymer nanoparticles, which was comparable with that for Taxol at the same 50 microg/mL drug concentration.