Interactions between fluorescein isothiocyanate and star-shaped polymer carriers studied by isothermal titration calorimetry (ITC)

• Thermodynamic classification of synthetic carriers proved to be useful.
• FITC exhibits high affinity for the star-shaped P(MMA-co-HAmPMA).
• Complete coverage of the carrier active groups has not always positive effect.
• Reaction effectiveness strongly depends on the polymer composition.
• P(MMA-co-HAmPMA) are very promissing as a dye carrier.

Isothermal titration calorimetry (ITC) technique was used to determine the thermodynamic parameters of reaction between fluorescein isothiocyanate (FITC) and novel star-shaped copolymers. Measurements were taken at 310.15 K using 0.64 g dm−3 NaCl, 0.5 g dm−3 Na2B4O7·10H2O in deionized water/methanol (60/40 v/v). Tested polymers belong to the innovative group of star-shaped copolymers with sugar core. Fluorescent FITC was chosen as one of the most reactive dye, which allowed monitoring the polymer behavior in physiological ionic strength conditions, as well as it was treated as the model biologically active substance. Analysis of the obtained calorimetric data allowed to determine the standard molar enthalpy of binding (ΔH○), the stoichiometry (n), the equilibrium constant (K), the standard Gibbs free energy change (ΔG○) and the standard entropy change (ΔS°), whose values allowed to obtain a wealth of information for the polymer-FITC binding, and identified the best carrier for the dye.