Characterizing the Partitioning Behavior of Drugs within PEO-b-PCL Copolymer Films

Poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) is a copolymer that has been researched for various medical applications, including drug delivery. In particular, the delivery of hydrophobic drugs is of interest as encapsulating the drug in a delivery system, such as PEO-b-PCL, can address the lack of bioavailability of hydrophobic drugs. Understanding how drugs partition within the amphiphilic PEO-b-PCL matrix is crucial for interpreting release profiles and developing effective drug delivery systems, as the partitioning efficiency is critical to the efficacy of the delivery. As an amphiphilic copolymer, PEO-b-PCL consists of both a hydrophilic and hydrophobic component. For that reason, the distribution of a drug within the polymer was examined as a function of its solubility in water. This study investigated the partitioning behavior of four low-risk drugs with varying solubilities - caffeine, ibuprofen, aspirin, and acetaminophen - through analysis of changes in polymer physical properties. The drugs were incorporated into films via the solvent-casting method, where both the polymer and drug were dissolved in chloroform, cast, and allowed to dry. The polymer films were made with varying weight percentages of the drug, ranging from 0 wt% to 200 wt%. Films were subjected to a thermal treatment and analyzed using Differential Scanning Calorimetry and Fourier Transform Infrared Spectroscopy to evaluate the crystallization point of each block, and by extension, their stabilities. The changes observed in the stability of a block are a first approximation to identify the drug affinity for one block or the other.