Synthesis and aggregation behavior of pluronic F87/poly(acrylic acid) block copolymer in the presence of doxorubicin

Poly(acrylic acid) (PAA) was polymerized on both termini of Pluronic F87 copolymer using the atom transfer radical polymerization technique to produce a novel block copolymer, PAA-b-F87-b-PAA (F87PAA). The loading of a cationic anticancer drug, doxorubicin (DOX), to F87PAA at different pH values was investigated using isothermal titration calorimetry (ITC), laser light scattering techniques, and UV-vis spectroscopy. At pH of 4.3-7.1, the ITC profile exhibited a significant exothermic peak, which indicated that the drug loading is an enthalpically driven process. At a pH of 4.3, the enthalpy maximum was significantly reduced in the presence of 2 M urea, indicating the existence of hydrogen bonds between the DOX and F87PAA copolymer. At a pH of 7.1, the fraction of bound DOX was close to the stoichiometric proportion of 1:1 to the molar concentration of carboxyl groups in the copolymer, where the drug loading is governed by electrostatic and stacking interactions. The TEM image of the complex indicated the formation of large compound micelles induced by the binding of DOX to the PAA segments.