Personalization of Complex Vaginal Inserts of Ethylene Vinyl Acetate via 3D-Printing

Ethylene vinyl acetate (EVA) with a vinyl acetate (VA) content of 28 wt.% (EVA28) is frequently used in vaginal inserts and subcutaneous implants due to its biocompatibility and drug-releasing properties. Traditionally being processed via hot melt extrusion, its processibility via filament-based 3D-printing was reported to be impossible. Consequently, no applicable customization concepts for vaginal inserts exist. For the first time, the fabrication of 3D-printed vaginal inserts (urethra pessaries) of EVA28 is demonstrated by optimizing its viscosity, employing 3D-printer adaptations, and carefully selecting printing parameters. The infill pattern of fully filled mono-material pessaries (determining the number and orientation of weld lines) significantly affects the in vitro release of the model drug progesterone (P4), while other critical parameters (the pessary's mechanical properties and appearance) remain unaffected. Weld lines act as diffusion barriers for dissolved P4 molecules. Hence, a high number of weld lines to be crossed reduces the overall P4 diffusivity in EVA28, decreasing the P4 release rate. To further control the P4 release, innovative multi-material pessary designs (additionally comprising EVA with a VA content of 9 wt.% that is also used in vaginal inserts) allow to tailor the in vitro drug release and the mechanics individually. Thereby, this work highly improves the mechanistic understanding on drug release modifications from 3D-printed non-biodegradable devices. The findings build the basis for the first application of customized vaginal inserts, as they are based on polymers used in corresponding marketed products for more than 20 years.