Self-assembly of interpolyelectrolyte complexes and mixed micelles from guanidinium and phosphonate derivatives of p–tert–butylthiacalix[4]arene and solubilization of paclitaxel

Abstract

In this work, supramolecular assemblies based on p–tert–butylthiacalix[4]arene derivatives functionalized with charged guanidinium and phosphonate fragments in the 1,3–alternate conformation were obtained in the presence of the surfactants. Two main approaches based on the macrocyclic compounds have been presented for supramolecular assembling, i.e. (i) the use of two oppositely charged macrocyclic compounds forming interpolyelectrolyte complexes; and (ii) the use of ionogenic macrocycles and low molecular surfactants forming mixed micelles. Self-assembling properties of guanidinium and phosphonate derivatives of p–tert–butylthiacalix[4]arene and paclitaxel solubilization of interpolyelectrolyte complexes and mixed micelles were examined and compared for various compositions. The obtained supramolecular associates were further investigated to load hydrophobic anticancer drug paclitaxel that is insoluble in water and requires solubilization prior to application. It was established that mixed micelles containing thiacalix[4]arene with guanidinium fragments were more effective in solubilizing paclitaxel against interpolyelectrolyte approach. The micelles obtained in the presence of water-insoluble drug formed stable monodisperse colloidal system consisted of spherical particles (d = 192 ± 7 nm, ζ = 33 ± 4 mV for equimolar ratio of the components). The results offer a new strategy for the design of the interpolyelectrolyte complexes based on the macrocyclic building blocks for the solubilization of water-insoluble drugs.