Improvements in Tissue Engineering and Regenerative Medicine (TERM)–type technologies have allowed the development of specific materials that, together with a better understanding of bone tissue structure, have provided new pathways to obtain biomaterials for bone tissue regeneration. In this manuscript, bioabsorbable materials are presented as emerging materials in tissue engineering therapies related to bone lesions because of their ability to degrade in physiological environments while the regeneration process is completed. This comprehensive review aims to explore the studies, published since its inception (2010s) to the present, on bioabsorbable composite materials based on PLA and PCL polymeric matrix reinforced with Mg, which is also bioabsorbable and has recognized osteoinductive capacity. The research collected in the literature reveals studies based on different manufacturing and dispersion processes of the reinforcement as well as the physicochemical analysis and corresponding biological evaluation to know the osteoinductive capacity of the proposed PLA/Mg and PCL/Mg composites. In short, this review shows the potential of these composite materials and serves as a guide for those interested in bioabsorbable materials applied in bone tissue engineering.

New clinical strategies for treating severe bone and cartilage injuries are required, especially for use in combination with implant procedures. For this purpose, p(VCL-co-HEMA) thermosensitive hydrogels have been activated with icariin-loaded nanoparticles to be used as bone-cell-harvesting platforms. Supercritical CO₂-SAS technology has been applied to encapsulate icariin, a small molecule that is involved in osteoblastic differentiation. Thus, physical-chemical analysis, including swelling and transmittance, showed the impact of HEMA groups in hydrogel composition. Moreover, icariin (ICA) release from p(VCL-co-HEMA) platforms, including pVCL@ICA nanoparticles, has been studied to evaluate their efficacy in relevant conditions. Finally, the thermosensitive hydrogels’ cell compatibility, transplant efficiency, and bone differentiation capacity were tested. This study identifies the optimal formulations for icariin-activated hydrogels for both control and HEMA formulations. Using this technique, osteoblastic sheets that were rich in collagen type I were successfully transplanted and recultivated, maintaining an optimal extracellular matrix (ECM) composition. These findings suggest a new cell-sheet-based therapy for bone regeneration purposes using customized and NP-activated pVCL-based cell platforms.

The current high production of plastics has prompted the exploration of alternative pathways to facilitate recycling, aiming for a progressively sustainable society. This paper presents an alternative and affordable technology for treating waste expanded polystyrene (EPS) mixed with acetone in a 100:1 volume ratio to be used as 3D printing ink for Direct Ink Write technology. In order to optimize the printing parameters, a comprehensive study was conducted, evaluating different needle diameters, printing speeds, and bed temperature values to achieve homogenous pieces and a highly repeatable 3D printing process. Results showed that the main optimum printing parameters were using needles with diameters of 14 to 16 G and printing speeds ranging from 2 to 12 mm/s, which were found to yield the most uniform ribbons. Increasing the bed temperature, despite favoring acetone evaporation, led to the generation of more heterogeneous structures due to void growth inside the printed ribbons. Thus, employing room temperature for the bed proved to be the optimal value. Lastly, a comparative study between the starting material and the EPS after the printing process was conducted using FTIR-ATR and GPC analyses, ensuring the preservation of the original polymer’s integrity during physical recycling.

Thermosensitive hydrogels based on the N-vinyl caprolactam (VCL), capable of allowing for cell adhesion and proliferation, as well as non-aggressive detachment by controlled temperature drop, were functionalized with 23 % or lower molar percentages of the cationizable hydrophobic unit 2-(diisopropylamino) ethyl methacrylate (DPAEMA), to obtain networks with dual sensitivity to temperature and pH. The swelling analysis of the systems has shown a transition pK (pK_b) close to physiological values, dependent on the temperature of the medium (pK_b of 6.6 and 6.9 when the temperature of the medium is above and below the transition temperature VPTT, respectively) and little dependence on the degree of functionalization of DPAEMA. In addition, at temperatures below the transition temperature (VPTT), the systems have shown large swelling variations as a function of the pH (i.e. below and above the pK_b), exhibiting greater absorption capacity at pHs below pK_b, where the DPAEMA units are cationized. Cytocompatibility and transplant capacity have been evaluated using the C166-GFP endothelial cell line. None of the thermosensitive hydrogels with variable DPAEMA content showed a delay with respect to the control without DPAEMA neither in terms of adhesion nor in proliferation. However, by increasing the percentage of DPAEMA functionalization -and decreasing thermosensitivity-, a correlative decrease in mitochondrial activity was obtained in the transplant, with significant differences for the hydrogels with DPAEMA molar percentage of 3 % or higher. Taking advantage of the proximity of the pK_b to the physiological value, we have evaluated the cellular response and the capacity for transplantation after lowering the pH to 6.5, below pK_b. A direct relationship of the DPAEMA functionalization degree on the detachment efficiency was observed, since the hydrogels with the highest molar load of DPAEMA showed higher mitochondrial metabolic activity after cell detachment.

This work investigates the sustainable reuse of expanded polystyrene (EPS) waste through a multi-cycle physical recycling process involving dissolution in acetone and subsequent manufacturing via Direct Ink Write (DIW) 3D printing and casting. Morphology and mechanical properties were evaluated as a function of the manufacturing technique and number of dissolution cycles. Morphological analysis revealed that casted specimens better replicated the target geometry, while voids in 3D-printed specimens aligned with the printing direction due to rapid solvent evaporation. These voids contributed to slightly reduced stiffness in 3D-printed specimens compared to casted ones, particularly for transverse printing orientation. The defoaming process during dissolution significantly increased the density of the material, as well as removed low molecular weight additives like plasticizers, leading to a notable enhancement in stiffness. Successive dissolution cycles led to increased removal of plasticizers, enhancing stiffness up to 52 times (cast), 42 times (longitudinally printed), and 35 times (transversely printed) relative to as-received EPS waste. The glass transition temperature remained unchanged, confirming the preservation of polymer integrity. This work highlights the potential of EPS inks for sustainable, multi-cycle recycling, combining enhanced mechanical performance with the flexibility of 3D printing for complex, cost-effective designs, aligning with circular economy principles.