3D-Bioprinting leads to the realization of tridimensional customized constructs to reproduce the biological structural complexity. The new technological challenge focuses on obtaining a 3D structure with several distinct layers to replicate the hierarchical organization of natural tissues. This work aims to reproduce large blood vessel substitutes compliant with the original tissue, combining the advantages of the 3D bioprinting, decellularization, and accounting for the presence of different cells. The decellularization process was performed on porcine aortas. Various decellularization protocols were tested and evaluated through DNA extraction, quantification, and amplification by PCR to define the adequate one. The decellularized extracellular matrix (dECM), lyophilized and solubilized, was combined with gelatin, alginate, and cells to obtain a novel bioink. Several solutions were tested, tuning the percentage of the components to obtain the adequate structural properties. The geometrical model of the large blood vessel constructs was designed with SolidWorks, and the construct slicing was done using the HeartWare software, which allowed generating the G-Code. The final constructs were 3D bioprinted with the Inkredible + using dual print heads. The composition of the bioink was tuned so that it could withstand the printing of a segment of a tubular construct up to 10 mm and reproduce the multicellular complexity. Among the several compositions tested, the suspension resulting from 8% w/v gelatin, 7% w/v alginate, and 3% w/v dECM, and cells successfully produced the designed structures. With this bioink, it was possible to print structures made up of 20 layers. The dimensions of the printed structures were consistent with the designed ones. We were able to avoid the double bioink overlap in the thickness, despite the increase in the number of layers during the printing process. The optimization of the parameters allowed the production of structures with a height of 20 layers corresponding to 9 mm. Theoretical and real structures were very close. The differences were 14% in height, 20% internal diameter, and 9% thickness. By tailoring the printing parameters and the amount of dECM, adequate mechanical properties could be met. In this study, we developed an innovative printable bioink able to finely reproduce the native complex structure of the large blood vessel.

Subretinal injection of gene products is the only treatment option for inherited retinal diseases. However, this procedure induces localized high multiaxial deformations, potentially causing irreversible tissue damage due to retinal overstretching and tearing. Comprehensive characterization of retinal mechanical behavior is essential for performing safe injections. Although uniaxial tensile test has been used in the literature, it has many limitations for retinal characterization. To date, retinal mechanical properties are poorly understood due to the lack of standardized testing protocol. This study aimed to introduce a combined experimental-computational approach using small punch testing and finite element simulations to investigate retina elastic behavior under biaxial deformations. To develop a suitable testing protocol for retinal samples, we evaluated the impact of environmental conditions on retinal elasticity by performing uniaxial tensile tests on porcine retinal strips in air, in a saline bath, and at different temperatures. The results showed that conditions did not significantly affect the elastic modulus. We then developed an easy and reproducible small punch test protocol, allowing to measure for the first time the load-displacement response of the retina under biaxial deformations. Computational simulations enabled the analysis of retinal deformations and the identification of its elastic modulus (5.5 kPa). The outcomes of this study highlight the great potential of the combined approach as a viable alternative to uniaxial tensile test to advance the understanding of retinal biomechanics. This is essential not only for minimizing sight-threatening surgical complications during injections, but also for building predictive in silico models, and developing biomimetic scaffolds.

There is an ongoing effort to advance methodologies for culturing functional photoreceptors in vitro for retinal regenerative strategies. To support the formation of functional photoreceptors, a scaffold should replicate the native environment. The aim of this study was to optimize a sodium alginate–gelatin (SA-G) bioink to mimic the retinal properties while ensuring the printing of constructs with high shape fidelity. The optimized bioink was thoroughly characterized in terms of its physical, mechanical, and rheological properties, printability assessment, and preliminary biocompatibility. The material showed a constant degradation rate, which is crucial for effective tissue regeneration as it provides support for cell differentiation and polarization while gradually degrading to allow cell proliferation and matrix deposition. The optimized bioink displayed stiffness comparable to the native photoreceptor layer, potentially providing appropriate mechanical cues for photoreceptor maturation. Additionally, it exhibited shear-thinning behavior, the presence of yield stress, and fast recovery kinetics, which are essential for successful extrusion. The high shape fidelity of 3D-printed constructs suggested the feasibility of printing complex patterns to drive photoreceptor polarization. The preliminary cell results demonstrated homogeneous cell distribution and sustained cell viability over time. Overall, these findings indicate that the optimized bioink can provide the mechanical and topographical cues necessary for cultivating photoreceptors in vitro for retinal regeneration.

Interface tissues, such as the enthesis connecting ligaments to bone, present multiphasic architectures with continuous gradients in structure, composition, and mechanics. Engineering such complex transitions remains a major challenge in biofabrication. This study aims to develop a hybrid manufacturing and machine learning (ML)-guided design strategy to create functionally graded scaffolds for anterior cruciate ligament (ACL) reconstruction. A hybrid biofabrication platform was used to integrate extrusion-based three-dimensional printing and electrospinning within a single workflow. Polycaprolactone was used as the common biomaterial for both modalities. Four scaffold designs, varying in electrospun midsection length, slit patterning, and core geometry, were fabricated to replicate the native ACL’s zonal architecture. Scaffolds were characterized through scanning electron microscopy (SEM) and uniaxial tensile testing. Resulting data were used to train a ML model to predict mechanical performance from geometric features. The model was then used to generate a fifth scaffold design optimized for enhanced performance. The hybrid process successfully fabricated multiscale scaffolds with integrated bone-like, enthesis-like, and ligament-like regions. SEM confirmed morphological integration between printed and electrospun structures. Mechanical testing revealed design-dependent variations in strength and stiffness. The ML model identified slit number and outer diameter as key predictors and guided the design of an optimized scaffold that combined the compliance of slitted geometries with enhanced mechanical strength. The ML-optimized scaffold achieved the highest tensile force among the slitted designs and improved stiffness compared to the other slitted configurations this study demonstrates a predictive and performance-driven biofabrication strategy that integrates hybrid additive manufacturing and ML. The approach enables rational scaffold optimization, reduces empirical iterations, and supports the development of biomimetic constructs for soft-to-hard tissue engineering. While focused on ACL reconstruction, the workflow is adaptable to a wide range of tissue interfaces.

Introduction: The integration of three-dimensional (3D) printing into Point‐of‐Care (POC) healthcare has enabled the rapid production of patient-specific medical devices, including anatomical models and surgical guides. However, the increasing use of additive manufacturing in clinical settings raises environmental concerns related to the consumption of virgin polymers and the generation of plastic waste. Circular economy approaches based on recycled materials may represent a more sustainable alternative, provided that the safety, biocompatibility, and manufacturing requirements of medical applications are preserved. This study investigated the feasibility of using chemically recycled acrylonitrile butadiene styrene (ABS) for the fabrication of non‐implantable medical devices by Fused Deposition Modeling (FDM). Methods: The chemically recycled ABS used in this study was produced using Versalis’ proprietary technology. The recycled ABS was first chemically characterized to assess its suitability for biomedical use. It was then processed into 1.75 mm filaments and used to manufacture standardized specimens and proof‐of‐concept patient‐specific devices in an ISO 13485‐certified laboratory. Dimensional accuracy and process repeatability were evaluated, while biological performance was assessed through direct cytotoxicity testing according to ISO 10993‐5 using L929 fibroblasts. The results were compared with those obtained using a certified medical‐grade ABS reference material. Results: Chemically recycled ABS showed a chemical profile compatible with current regulatory requirements and was successfully processed into high‐quality FDM filaments and printed components. The printed specimens demonstrated high dimensional accuracy and reproducibility, supporting the suitability of the material for geometrically demanding medical applications. Cytotoxicity testing confirmed that the recycled ABS was non-cytotoxic in all tested forms, with 3D-printed samples showing a cytocompatibility profile comparable to that of the certified medical-grade ABS reference material. In addition, patient‐specific anatomical models and surgical guides were successfully fabricated, demonstrating the applicability of the material within clinically relevant POC workflows. Discussion: Overall, these findings indicate that chemically recycled ABS represents a promising and sustainable alternative to virgin polymers for the FDM manufacturing of non‐implantable medical devices. This study provides evidence that circular materials can be integrated into hospital‐based additive manufacturing without compromising the safety, biocompatibility, or manufacturing performance evaluated in this study, thereby supporting the transition toward more sustainable Point‐of‐Care production systems.