Effects of conditions for preparing nanoparticles composed of aminoethylcarbamoyl-β-cyclodextrin and ethylene glycol diglycidyl ether on trap efficiency of a guest molecule

Nanoparticles comprising copolymers of aminoethylcarbamoyl-β-cyclodextrin (AEC-β-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 μm) are formed under the condition of 5.0% water and 5.0% surfactant, which have the highest β-CD contents (75.5 wt.%) and the most positive ζ-potential (53.6 mV). The ζ-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 ζ-potential of the particles; viz., the particles with ζ-potential of 53.6 mV show the highest efficiency of uptake. The diameter and the β-CD contents are closely related with the water/surfactant ratio, and the ζ-potentials are dependent on both the diameter and the β-CD contents. Inclusion of ANS into the CD cavity of EGDGE/AEC-β-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.