PEO–PPO based star-block copolymer T904 as pH responsive nanocarriers for quercetin: Solubilization and release study

Solubilization of quercetin (QN), a hypolipidemic drug in aqueous micellar solution of a star-like octablock Tetronic® T904 covering different salt concentration, pH and temperature is investigated. The change in pH modulates the charge of the copolymer which alters the dibasic nature of the centrally located ethylenediamine moiety and makes T904 undergo deprotonation favoring self assembly. At low pH, the columbic repulsion among the positively charged amine groups of Tetronic® hinders micellization while presence of salt facilitates it. The drug solubility data for micelles in aqueous/salt solutions determined by UV–Visible spectroscopy and micellar size with loaded drug from dynamic light scattering (DLS) are reported. Hydrophobic/anionic QN, deprotonates T904 and induces the micellization in acidic pH thus assisting solubilization. The expected locus (site) of the QN in T904 micelles was successfully correlated by the significant and positive cross peaks obtained from two-dimensional nuclear Overhauser effect spectroscopy (2D-NOESY). The evaluated in vitro release profile employing different kinetic models explains the controlled release of drug from T904 micelles.

Graphical abstractSolubilizate dissolution of QN (anionic drug) in T904 core-shell aggregates possessing nonpolar PPO interior and relatively polar PEO shells is well presented as a function of pH.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Star-block copolymer shows efficient encapsulation toward hydrophobic drug. ► pH responsive stable polymer-drug complexation. ► QN encapsulated T904 micelles characterized by spectral and scattering techniques. ► Controlled release of drug from Tetronic micelles as inferred by kinetic models.