Ethylene vinyl acetate (EVA) with a vinyl acetate (VA) content of 28 wt.%(EVA28) is frequently used in vaginal inserts and subcutaneous implants dueto its biocompatibility and drug-releasing properties. Traditionally beingprocessed via hot melt extrusion, its processibility via filament-based3D-printing was reported to be impossible. Consequently, no applicablecustomization concepts for vaginal inserts exist. For the first time, thefabrication of 3D-printed vaginal inserts (urethra pessaries) of EVA28 isdemonstrated by optimizing its viscosity, employing 3D-printer adaptations,and carefully selecting printing parameters. The infill pattern of fully filledmono-material pessaries (determining the number and orientation of weldlines) significantly affects the in vitro release of the model drug progesterone(P4), while other critical parameters (the pessary’s mechanical properties andappearance) remain unaffected. Weld lines act as diffusion barriers fordissolved P4 molecules. Hence, a high number of weld lines to be crossedreduces the overall P4 diffusivity in EVA28, decreasing the P4 release rate. Tofurther control the P4 release, innovative multi-material pessary designs(additionally comprising EVA with a VA content of 9 wt.% that is also used invaginal inserts) allow to tailor the in vitro drug release and the mechanicsindividually. Thereby, this work highly improves the mechanisticunderstanding on drug release modifications from 3D-printednon-biodegradable devices. The findings build the basis for the firstapplication of customized vaginal inserts, as they are based on polymers usedin corresponding marketed products for more than 20 years.
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