Nanoparticles comprising copolymers of aminoetllylcarbamoyl-beta-cyclodextrin (AEC-beta-CD) and ethylene glycol diglycidyl ether (EGDGE) are prepared by an interfacial polyaddition reaction in a miniemulsion system. Polymers are formed in a W/O emulsion containing 0.25-10.0% (w/w) water and 5.0% (w/w) surfactant (MO-3S, tetraglycerin monoester, HLB 8.8), where simple particles are predominantly obtained when the water content is 1.0% and 5.0%. Notably, nano-size small particles (diameter: 0.3 mu m) are formed under the condition of 5.0% water and 5.0% surfactant, which have the highest beta-CD contents (75.5 wt.%) and the most positive xi-potential (53.6 mV). The xi-potential measurement indicates that the obtained particles have positive charge due to protonation of their amino groups below around pH 10. Actually, uptake of 8-anilino-1-naphthalenesulfonic acid (ANS) bearing negative charge (SO3-) and moderate hydrophobicity depends on the magnitude of xi-potential of the particles; viz., the particles with xi-potential of 53.6 mV show the highest efficiency of uptake. The diameter and the P-CD contents are closely related with the water/surfactant ratio, and the xi-potentials are dependent on both the diameter and the R-CD contents. Inclusion of ANS into the CD cavity of EGDGE/AEC-beta-CD particles can be controlled by electrostatic interaction between ANS (negatively charged) and the particle (positively charged). Namely, synergistic effect of cavity-inclusion and electrostatic interaction can dominate the uptake of guest molecules by the particles. (c) 2005 Elsevier B.V. All rights reserved.