The growing interest in biodegradable scaffolds for bone regeneration created a need to investigate new materials suitable for scaffold formation. Poly(lactic acid) (PLA) is a polymer commonly used in biomedical engineering, e.g. in tissue engineering as a biodegradable material. However, the mechanical behavior of PLA along its degradation time is still not explored well. For this reason, the mechanical properties of PLA scaffolds affected by incubation in physiological medium needs to be investigated to show the potential of PLA to be used as a material for biodegradable scaffold formation. The purpose of this research is to determine the mechanical properties of PLA scaffolds before and after incubation, and to apply constitutive material models for further behavior prediction. Two sets of PLA scaffolds were printed by the 3D printer “Prusa i3 MK3S” and sterilized by ultraviolet light and ethanol solution. The first set of specimens was incubated in DMEM (Dulbecco’s Modified Eagle Medium) for 60, 120, and 180 days maintaining 36.5 °C temperature. The mechanical properties of the scaffolds were determined after performing the compression test in the “Mecmesin MultiTest 2.5-i” testing stand with a force applied at two different speed modes. The obtained data was curve fitted with the hyperelastic material models for a model suitability study. The second set of specimens was incubated in PBS (Phosphate Buffered Saline) for 20 weeks and used in a polymer degradation study. The obtained results show that the mechanical properties of PLA scaffolds do not decrease during incubation in physiological medium for a predicted new bone tissue formation period, though hydrolysis starts at the very beginning and increases with time. PLA as a material seems to be suitable for the use in bone tissue engineering as it allows to form biocompatible and biodegradable scaffolds with high mechanical strength, required for effective tissue formation.

Objectives: Functional mitral regurgitation (FMR) remains challenging to repair surgically, as highlighted by the Cardiothoracic Surgical Trials Network (CTSN) trial, which showed limited durability of mitral annuloplasty. We previously demonstrated in vivo and experimentally that papillary muscle approximation (PMA) can improve mitral valve (MV) function, with or without annuloplasty. In this study, we assessed valve biomechanics after PMA, mitral annuloplasty, and their combination in imaging-derived computational models. Methods: 3D echo images were obtained in three pigs with heart failure, dilated ventricles, and FMR. Each echo dataset was segmented, and a subject-specific computational model of the MV was created. Virtual FMR repair was performed on each valve using PMA, annuloplasty with true-sized (40 mm) and downsized (38 mm and 36 mm) rings, and a combination of both techniques. For each repair strategy, leaflet closure was simulated, and MV geometry and biomechanics at peak systole were evaluated. Results: Isolated PMA improved valve coaptation, reduced leaflet stresses and chordal tension forces, but failed to completely eliminate FMR. Isolated mitral annuloplasty also improved coaptation, but overall provided only limited geometric and biomechanical benefits. Combining annuloplasty and PMA resulted in the most favorable outcomes, eliminating FMR, increasing coaptation length (up to 97.7%), and reducing leaflet stresses (up to 43.7%) and chordal forces (up to 43.0%). Conclusions: While both PMA and annuloplasty independently improved MV function, neither technique fully resolved FMR on its own. Their combination yielded the most favorable repair outcomes, eliminating FMR and significantly improving valve geometry and biomechanics without the need for excessive annular downsizing.