Smart microgel studies. Polyelectrolyte and drug-absorbing properties of microgels from polyether-modified poly(acrylic

The study dealt with microgels that consist of loosely cross-linked poly(acrylic acid) onto which poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) copolymers such as Pluronic F127 (average composition EO99PO67EO99) or L92 (EO8PO52EO8) segments are grafted. Microgels based on the more hydrophobic Pluronic L92 exhibited highly porous structure, while the microgels containing Pluronic F127 were generally larger and possessed smooth surfaces, a homogeneous structure, and lower ion-exchange capacity. A good correlation was observed between the microgel surface potential obtained from the potentiometric titration data and the independently measured electrophoretic zeta-potential. The differences in the microgel ion-exchange capacity account for the differences in the capacity of the microgels to absorb weakly basic anticancer drugs such as mitomycin, mitoxantrone, and doxorubicin. The uptake of hydrophobic drugs such as Taxol, estradiol, progesterone, and camptothecin was dictated by the content of PPO in the microgels, which determines their solubilizing capacity. The exclusion of proteins of varying molecular weight by the microgels reveals the effective pore size, which is below 7.5 nm in the F127-based microgels but is on the order of tens of nanometers in the L92-based microgels.