<i>Effect of Formulation Components on Surface Free Energy of Orodispersible Films</i>

ObjectiveSurface free energy was demonstrated to be a useful formulation-guiding parameter relevant to the surface wettability of orodispersible film substrates, while also providing insight into disintegration behavior.SignificanceInkjet printing is a promising technology for on-demand and personalized pharmaceutical manufacturing; however, inadequate printability caused by uncontrolled ink spreading or poor adhesion remains a practical challenge. The role of substrate surface properties in orodispersible film formulation design has not been systematically addressed.MethodsOrodispersible films were prepared using hydroxypropyl methylcellulose as the film-forming polymer, glycerol as a plasticizer, and model active pharmaceutical ingredients. A central composite design was applied to evaluate the effects of formulation factors on total and polar components of surface free energy, determined by contact angle measurements using the Owens-Wendt method. Disintegration time and tensile strength were evaluated.ResultsSurface free energy was influenced by formulation variables in an active pharmaceutical ingredient-dependent manner. Increased plasticizer and active pharmaceutical ingredient content reduced total and polar surface free energy components, whereas polymer concentration contributed positively. A significant negative correlation was observed between surface free energy and disintegration time, indicating that enhanced wettability promoted faster film disintegration. No direct correlation was found between surface free energy and tensile strength. Response surface modeling enabled identification of formulation regions balancing surface free energy, disintegration behavior, and mechanical strength.ConclusionsSurface free energy was demonstrated to be a useful formulation-guiding parameter for understanding the surface wettability of orodispersible film substrates relevant to pharmaceutical printing processes, while also providing insight into disintegration behavior.