Microphase Structure and Component Influence on Drug Sorption: Polyurethane-Drug Interaction Elucidation in Medical Catheter Systems

Polyurethanes are predominant materials for medical catheter manufacturing owing to their favorable physicochemical properties and biocompatibility. However, the drug-polyurethane interactions compromise therapeutic infusion efficacy and restrict its application in intravenous tubing. There are gaps in systematic research on sorption mechanisms pertaining to polyurethane infusion systems. This study investigates the structure–sorption relationship between polyurethane and active pharmaceutical ingredients (APIs), through combined investigations of dynamic sorption kinetics, static equilibrium sorption, and molecular dynamics simulations. It was revealed that enhanced molecular interactions in highly microphase-mixing polyurethanes reduced the free volume, thereby decreasing drug diffusion rates. The API sorption process exhibits three-stage Fickian diffusion behaviors. Equilibrium drug sorption concentration and equilibrium drug sorption capacity can be calculated from the initial drug concentration. Freundlich constant ( K f ) and partition coefficient ( K ) effectively represent the drug sorption capacity. Molecular dynamics simulations further quantify binding energetics, identifying Lennard–Jones short-range (LJ-SR) interactions as the predominant driver of drug-polymer adhesion. These findings provide insights for optimizing polyurethane formulations to minimize drug sorption and maintain therapeutic efficacy.