Thermodynamic properties of aqueous PEO–PPO–PEO micelles of varying hydrophilicity with added cisplatin determined by differential scanning calorimetry

Abstract

Differential scanning calorimetry was performed on a series of aqueous solutions of polyethylene oxide–polypropylene oxide–polyethylene oxide, PEO–PPO–PEO (L101, P104, P105, and F108), amphiphiles in the low concentration regime (0–2 % mass v−1) to resolve the critical micelle concentrations of the neat polymers. Work was done from 2 to 10 % mass v−1 (in 2 % mass v−1 increments) amphiphilic copolymer concentrations and co-formulated with cisplatin concentrations (0–0.1 % mass v−1 in 0.02 % mass v−1 increments) to resolve any deviation in the enthalpy of micelle formation. Enthalpy–entropy compensation plots for each neat copolymer and each amphiphile solution mixed with cisplatin were obtained. Two types of behaviors were observed: a drug-influenced compensation temperature profile (P104) and a drug-invariant behavior (L101, P05, and F108) where the change in compensation temperature was <1 °C. Only neat P104 was found to be profoundly influenced by the presence of cisplatin that must reorganize the core–shell interface between the hydrophobic and hydrophilic regions of the micelle. Adding cisplatin lowered Tcompensation from 302.1 to 288.8 K for Pluronic P104.