3D printing of customized all-starch tablets with combined release kinetics

[EN] Starch-based tablets with tailored releases were prepared by 3D printing using a hydrophobic drug. The importance of the origin of the excipient in the inks and tablets was analyzed. Besides, the effect of the geometry of the tablet on the drug release profile was also evaluated. The rheological properties of the inks was influenced by the botanic origin of the starch. Consequently, tablets presented different microporous structure and particular compression and swelling behaviors. Normal maize starch showed a non-well-defined porous morphology, not being able to form a stable structure whereas, waxy maize and potato starches exhibited a well-defined porous structure and were both able to maintain their integrity after long time immersion. Finally, tablets combining different starches and geometries were printed tailoring the drug release from 10 min to 6 h and designing two-steps profiles. The applicability of the developed 3D printed drug release systems in personalized therapies was demonstrated.Financial support from the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), from the Basque Government in the frame of Elkartek KK-2020/00053 and PIBA2020-1-0041 and from Spanish Ministry of Science and Innovation and Spanish State Research Agency (MCIN/AEI/10.13039/501100011033) in the frame of PID2019-105090RB-I00 project, are gratefully acknowledged. Moreover, we are grateful to the Macrobehavior-Mesostructure-Nanotechnology SGIker unit of the UPV/EHU. K. González thanks the University of the Basque Country for the grant “Contratación de doctores recientes hasta su integración en programas de formación postdoctoral en la UPV/EHU «DOKBERRI» 2020-I” (DOCREC20/07)

Development of a Novel Biobased Polyurethane Resin System for Structural Composites

Polyurethanes are gaining increasing interest for their use as structural components subjected to cyclic loads, such as leaf springs. Thermoset polyurethane (PUR) based technology offers some advantages, such as fatigue resistance, low viscosity, and fast curing. However, current PUR formulations present two major drawbacks: their petrochemical origin and high reactivity. The aim of this work was to develop a novel biobased PUR (BIO-PUR) with the required mechanical properties and processability for manufacturing structural composites by resin transfer moulding (RTM). For this purpose, a high functionality and high hydroxyl index castor-oil-based polyol was used combined with a biobased glycerol (BIO-Gly) to increase the crosslinking density and improve the final properties of the BIO-PUR. The viscosity and reactivity of the different systems were studied by means of rheology tests and differential scanning calorimetry (DSC). Thermal and mechanical properties were studied by dynamic mechanical analysis (DMA) and flexural tests. Furthermore, the RTM process of a representative part was simulated and validated through the manufacturing and testing of plates. The properties of the BIO-PUR resin systems were strongly influenced by the addition of biobased glycerol and its effect on the crosslinking density. The combination of a high functionality and hydroxyl index biobased polyol with the biobased glycerol resulted in a high-performance BIO-PUR with the required reactivity and final properties for structural applications.This research was funded by the Basque Government through the ELKARTEK 2021 (Project NEOMAT KK-2021/00059) and in the frame of Grupos Consolidados (IT-1690-22) and by the University of the Basque Country (UPV/EHU) in the frame of GIU18/216 Research Group

Design of a Waterborne Polyurethane-Urea Ink for Direct Ink Writing 3D Printing

In this work, polycaprolactone–polyethylene glycol (PCL–PEG) based waterborne polyurethane–urea (WBPUU) inks have been developed for an extrusion-based 3D printing technology. The WBPUU, synthesized from an optimized ratio of hydrophobic polycaprolactone diol and hydrophilic polyethylene glycol (0.2:0.8) in the soft segment, is able to form a physical gel at low solid contents. WBPUU inks with different solid contents have been synthesized. The rheology of the prepared systems was studied and the WBPUUs were subsequently used in the printing of different pieces to demonstrate the relationship between their rheological properties and their printing viability, establishing an optimal window of compositions for the developed WBPUU based inks. The results showed that the increase in solid content results in more structured inks, presenting a higher storage modulus as well as lower tan δ values, allowing for the improvement of the ink’s shape fidelity. However, an increase in solid content also leads to an increase in the yield point and viscosity, leading to printability limitations. From among all printable systems, the WBPUU with a solid content of 32 wt% is proposed to be the more suitable ink for a successful printing performance, presenting both adequate printability and good shape fidelity, which leads to the realization of a recognizable and accurate 3D construct and an understanding of its relationship with rheological parameters.Financial support from the University of the Basque Country (UPV/EHU) (GIU18-216), Spanish Ministry of Economy and Competitiveness (MINECO) (MAT2016-76294R and PID2019-105090RB-I00) and the Basque Government (KK-2019/00048) are gratefully acknowledged. Julen Vadillo wishes to acknowledge both the University of Pau and Pays de l’Adour and the UPV/EHU for his PhD grant

Enhancing the Mechanical Properties of 3D-Printed Waterborne Polyurethane-Urea and Cellulose Nanocrystal Scaffolds through Crosslinking

In this work, shape-customized scaffolds based on waterborne polyurethane-urea (WBPUU) were prepared via the combination of direct ink writing 3D-printing and freeze-drying techniques. To improve the printing performance of the ink and guarantee a good shape fidelity of the scaffold, cellulose nanocrystals (CNC) were added during the synthesis of the WBPUU and some of the printed constructs were immersed in CaCl2 prior to the freeze-drying process to promote ionic crosslinking between calcium ions and the polyurethane. The results showed that apart from allowing the ink to be successfully printed, obtaining scaffolds with good shape fidelity, the addition of the CNC resulted in a greater homogeneity of the porous structure as well as an increase of the swelling capacity of the scaffolds. Additionally, the CNC has a reinforcement effect in the printed systems, presenting a higher compression modulus as the CNC content increases. In the case of samples crosslinked by calcium ions, a rigid shell was observed by scanning electron microscopy, which resulted in stiffer scaffolds that presented a lower water absorption capacity as well as an enhancement of the thermal stability. These results showed the potential of this type of post-printing process to tune the mechanical properties of the scaffold, thus widening the potential of this type of material.The financial support of the Basque Government within the framework of Grupos Consolidados (IT-1690-22) and the Spanish Ministry of Science and Innovation (MINCIN)—State Investigation Agency (AEI) (PID2019-105090RB-I00/AEI/10.13039/501100011033) is acknowledged

Residues from rigid foams and graphene for the synthesis of hybrid polyurethane flexible foams composites

Hybrid biobased polyurethane flexible foam composites containing a residue from surf industry (polyurethane powder) as filler and graphite or graphene residue were synthe-sized. It was observed that the addition of the powder at low contents did not modify the final properties considerably, since the cell structure was not compromised. Moreover, the powder increased the capacity of the foams to retain the carbonaceous fillers. The compressive properties of the hybrid foams were not altered with the addition of the graphite and graphene. Finally, hybrid composites showed selective absorption capacity since the presence of the carbonaceous fillers provided the foams oil absorption capacity without modifying the hydrophobic nature of the matrix foams. (C) 2021 The Author(s). Published by Elsevier B.V.Authors thank the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), the Basque Government (PIBA19-0044 project) and the Provincial Country of Gipuzkoa (DG 19/28 Support Program for the Guipuzcoan Science, Technology and Innovation Network 2019) for the financial support. We also acknowledge the "Macrobehavior-Mesostructure-Nanotechnology " SGIker unit from the UPV/EHU, for their technical support and Olatu S.A. (Gipuzkoa) for providing the PUP. T.C-C. thanks the Provincial Country of Gipuzkoa (2017-BE01-000002-01) and the UPV/EHU (ESPDOC19/41)

Effect of Cellulose Nanofibers’ Structure and Incorporation Route in Waterborne Polyurethane–Urea Based Nanocomposite Inks

In order to continue the development of inks valid for cold extrusion 3D printing, waterborne, polyurethane–urea (WBPUU) based inks with cellulose nanofibers (CNF), as a rheological modulator, were prepared by two incorporation methods, ex situ and in situ, in which the CNF were added after and during the synthesis process, respectively. Moreover, in order to improve the affinity of the reinforcement with the matrix, modified CNF was also employed. In the ex situ preparation, interactions between CNFs and water prevail over interactions between CNFs and WBPUU nanoparticles, resulting in strong gel-like structures. On the other hand, in situ addition allows the proximity of WBPUU particles and CNF, favoring interactions between both components and allowing the formation of chemical bonds. The fewer amount of CNF/water interactions present in the in situ formulations translates into weaker gel-like structures, with poorer rheological behavior for inks for 3D printing. Stronger gel-like behavior translated into 3D-printed parts with higher precision. However, the direct interactions present between the cellulose and the polyurethane–urea molecules in the in situ preparations, and more so in materials reinforced with carboxylated CNF, result in stronger mechanical properties of the final 3D parts.Financial support from the Basque Government (Grupos Consolidados (IT-1690-22), Elkartek (KK19-00048)) is acknowledged

Cellulose and Graphene Based Polyurethane Nanocomposites for FDM 3D Printing: Filament Properties and Printability

3D printing has exponentially grown in popularity due to the personalization of each printed part it offers, making it extremely beneficial for the very demanding biomedical industry. This technique has been extensively developed and optimized and the advances that now reside in the development of new materials suitable for 3D printing, which may open the door to new applications. Fused deposition modeling (FDM) is the most commonly used 3D printing technique. However, filaments suitable for FDM must meet certain criteria for a successful printing process and thus the optimization of their properties in often necessary. The aim of this work was to prepare a flexible and printable polyurethane filament parting from a biocompatible waterborne polyurethane, which shows potential for biomedical applications. In order to improve filament properties and printability, cellulose nanofibers and graphene were employed to prepare polyurethane based nanocomposites. Prepared nanocomposite filaments showed altered properties which directly impacted their printability. Graphene containing nanocomposites presented sound enough thermal and mechanical properties for a good printing process. Moreover, these filaments were employed in FDM to obtained 3D printed parts, which showed good shape fidelity. Properties exhibited by polyurethane and graphene filaments show potential to be used in biomedical applications

Enzymatic upgrading of nanochitin using an ancient lytic polysaccharide monooxygenase

Numerous enzymes have the potential to upgrade biomass, converting it into high-tech materials for new applications. However, the features of natural enzymes often limit their use beyond chemical conversion of the substrate. The development of strategies for the enzymatic conversion of biomass into high-value materials may broaden the range of applications of enzymes and enzyme design techniques. A relevant case is lytic polysaccharide monooxygenase (LPMO), a class of enzymes that catalyzes the oxidative cleavage of glycosidic bonds. Here, we show that an ancestral LPMO can generate chitin nanocrystals. Physicochemical characterization of the chitin nanocrystals demonstrates modifications that make it superior compared to chitin obtained by chemical treatments. We show that the nanocrystals are suitable for controlled 2D and 3D cell cultures, as well as for engineering a biomatrix that combines with graphene oxide, forming a hybrid conductive bioink.This work has been supported by grants PID2019-109087RB-I00 to R.P.-J. from Spanish Ministry of Science and Innovation. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 964764 to R.P.-J. ‘Materials + Technologies’ Research Group also acknowledges UPV/EHU and the Basque Government in the frame of “Research Group” (GIU 18/216) and “Grupos Consolidados” (IT776-13), respectively. We also thank Gipuzkoako Foru Aldundia for financial Support. HEK293T cells were a kind gift from Dr. Maria Muñoz Caffarel (Biodonostia, San Sebastian, Spain)

Design and Characterization of Waterborne Polyurethane-Urea based Nanocomposites for 3D Printing

335 p.Polyurethane-ureas are very versatile polymers that can be process in many ways and used in an extremely wide field of applications. At the same time, 3D printing offers the opportunity to make one on one personalized designs, a quality remarkably beneficial for the biomedical field. In this work, the use of a waterborne polyurethane-urea synthesized for its used in 3D printing is studied. The addition of different nanoentities is analyzed, such as cellulose nanofibers, carboxylated nanofibers, graphene oxide, graphene and natural extracts and their effect on the printability and properties of the materials is assessed. The potential of these nanocomposites for two 3D printing methods is analyzed, namely fused deposition modeling and direct ink writing

Influence of Process Parameters in Graphene Oxide Obtention on the Properties of Mechanically Strong Alginate Nanocomposites

Sodium alginate, a biopolymer extracted from brown algae, has shown great potential for many applications, mainly due to its remarkable biocompatibility and biodegradability. To broaden its fields of applications and improve material characteristics, the use of nanoreinforcements to prepare nanocomposites with enhanced properties, such as carbonaceous structures which could improve thermal and mechanical behavior and confer new functionalities, is being studied. In this work, graphene oxide was obtained from graphite by using modified Hummers’ method and exfoliation was assisted by sonication and centrifugation, and it was later used to prepare sodium alginate/graphene oxide nanocomposites. The effect that different variables, during preparation of graphene oxide, have on the final properties has been studied. Longer oxidation times showed higher degrees of oxidation and thus larger amount of oxygen-containing groups in the structure, whereas longer sonication times and higher centrifugation rates showed more exfoliated graphene sheets with lower sizes. The addition of graphene oxide to a biopolymeric matrix was also studied, considering the effect of processing and content of reinforcement on the material. Materials with reinforcement size-dependent properties were observed, showing nanocomposites with large flake sizes, better thermal stability, and more enhanced mechanical properties, reaching an improvement of 65.3% and 83.3% for tensile strength and Young’s modulus, respectively, for a composite containing 8 wt % of graphene oxide.This research was funded by Spanish Ministry of Science, Innovation and Universities in the frame of MAT2016-76294-R project, the Basque Government for PIBA 2019-44 project and the Gipuzkoa Council in the frame of Programa de Red Gipuzkoana de Ciencia, Tecnología e Innovación 2019