A Study of the Printability of Alginate-Based Bioinks by 3D Bioprinting for Articular Cartilage Tissue Engineering

Three-dimensional bioprinting combined with natural hydrogels is a promising technology for the treatment of several pathologies and different tissue regeneration. One of the most studied tissues is cartilage, a complex and avascular tissue that displays a limited self-repair capacity after injuries. Herein, the development of alginate-based hydrogels and scaffolds containing different microstructure is presented and the printability of alginate by 3D bioprinting is studied. Rheological characterization was performed for the determination of viscosity and viscoelastic properties of hydrogels and mechanical characterization was carried out for the determination of compressive modulus of alginate hydrogels. All these characteristics were correlated with alginate behaviour during 3D bioprinting process. For the printability evaluation filament diameter, perimeter of the pores, area of the pores and shrinkage of alginate scaffolds were measured. The results demonstrate that alginate microstructure has a great influence on its printability and on hydrogels’ physicochemical properties. Molecular weight of alginate determines its viscosity while M/G ratio determines cross-linking conditions and mechanical properties that vary with cross-linking density. These results suggest the importance of an exhaustive control of the viscoelastic and mechanical properties of alginate hydrogels to obtain structures with high resolution and precision

Critical Study on the Tube-to-Chip Luer Slip Connectors.

Luer slip is one of the gold standards for chip-to-world interface in microfluidics. They have outstanding mechanical and operational robustness in a broad range of applications using water and solvent-based liquids. Still, their main drawbacks are related to their size: they have relatively large dead volumes and require a significant footprint to assure a leak-free performance. Such aspects make their integration in systems with high microchannel density challenging. To date, there has been no geometrical optimization of the Luer slips to provide a solution to the mentioned drawbacks. This work aims to provide the rules toward downscaling the Luer slips. To this effect, seven variations of the Luer slip male connectors and five variations of Luer slip female connectors have been designed and manufactured focusing on the reduction of the size of connectors and minimization of the dead volumes. In all cases, female connectors have been developed to pair with the corresponding male connector. Characterization has been performed with a tailor-made test bench in which the closure force between male and female connectors has been varied between 7.9 and 55 N. For each applied closure force, the test bench allows liquid pressures to be tested between 0.5 and 2.0 bar. Finally, the analysis of a useful life determines the number of cycles that the connectors can withstand before leakage.The authors are grateful for the financial support from the Basque Country Government within the frame of the project BIKAINTEK 2018 (48-AF-W2-2018-00006)

Validation of HepG2/C3A Cell Cultures in Cyclic Olefin Copolymer Based Microfluidic Bioreactors

Organ-on-chip (OoC) technology is one of the most promising in vitro tools to replace the traditional animal experiment-based paradigms of risk assessment. However, the use of OoC in drug discovery and toxicity studies remain still limited by the low capacity for high-throughput production and the incompatibility with standard laboratory equipment. Moreover, polydimethylsiloxanes, the material of choice for OoC, has several drawbacks, particularly the high absorption of drugs and chemicals. In this work, we report the development of a microfluidic device, using a process adapted for mass production, to culture liver cell line in dynamic conditions. The device, made of cyclic olefin copolymers, was manufactured by injection moulding and integrates Luer lock connectors compatible with standard medical and laboratory instruments. Then, the COC device was used for culturing HepG2/C3a cells. The functionality and behaviour of cultures were assessed by albumin secretion, cell proliferation, viability and actin cytoskeleton development. The cells in COC device proliferated well and remained functional for 9 days of culture. Furthermore, HepG2/C3a cells in the COC biochips showed similar behaviour to cells in PDMS biochips. The present study provides a proof-of-concept for the use of COC biochip in liver cells culture and illustrate their potential to develop OoC.This research was funded by Basque Country Government within the frame of the project BIKAINTEK 2018 (48-AF-W2-2018-00006). Taha Messelmani PhD is funded by ANR (Agence National de la Recherche, France, MIMLIVEROnChip ANR-19-CE19-0020-01 project)

Natural Hydrogels Support Kidney Organoid Generation and Promote in vitro Angiogenesis

To date strategies aiming to modulate cell to extracellular matrix (ECM) interactions during organoid derivation remain largely unexplored. Here renal decellularized extracellular matrix (dECM) hydrogels are fabricated from porcine and human renal cortex as biomaterials to enrich cell-to-ECM crosstalk during the onset of kidney organoid differentiation from human pluripotent stem cells (hPSCs). Renal dECM-derived hydrogels are used in combination with hPSC-derived renal progenitor cells to define new approaches for 2D and 3D kidney organoid differentiation, demonstrating that in the presence of these biomaterials the resulting kidney organoids exhibit renal differentiation features, and the formation of an endogenous vascular component. Based on these observations, a new method to produce kidney organoids with vascular-like structures is achieved through the assembly of hPSC-derived endothelial-like organoids with kidney organoids in 3D. Major readouts of kidney differentiation and renal cell morphology are assessed exploiting these culture platforms as new models of nephrogenesis. Overall, this work shows that exploiting cell-to-ECM interactions during the onset of kidney differentiation from hPSCs facilitates and optimizes current approaches for kidney organoid derivation thereby increasing the utility of these unique culture cell platforms for personalized medicine

The Importance of Coupling Agent on Tensile and Thermomechanical Performance of Annealed Composites Based on Poly(Lactic Acid)/Poly(Methyl Methacrylate) Matrix and Sisal Fiber Bundles

The main aim of this work is to study the importance of the coupling agent on tensile and thermomechanical performance of annealed composites based on poly (lactic acid)/poly (methyl methacrylate) matrix and sisal fiber bundles. As coupling agent poly (styrene-co-glycidyl methacrylate) copolymer was used. Results obtained in the current study suggested that the presence of the copolymer is crucial to form a strong adhesion between the fibers and polymeric matrix and consequently to improve both thermomechanical performance and tensile properties after annealing process. It must highlight that the estimated heat deflection temperature (HDT) of annealed composite with 40 wt% of fiber increased around 40 ºC respect to respect to commercial neat PLA.This work was supported by the Eusko Jaurlaritza [KK-2018/00046]; Ministerio de Ciencia y Tecnología [PID2019-105090RB-I00

Preparation and characterization of composites based on poly(lactic acid)/poly(methyl methacrylate) matrix and sisal fiber bundles: The effect of annealing process

The interest on poly(lactic acid) (PLA)/poly(methyl methacrylate) (PMMA) blends has increased during the last years due to their promising properties. The novelty of the current work focuses on the preparation and characterization of biocomposites based on PLA/PMMA matrix and NaOH-treated sisal fibers. The effect of the addition of treated sisal fibers on the physico-mechanical properties of high polylactide content composites was studied. For this purpose, PLA/PMMA blend (80/20 wt%) was prepared by melt-blending and reinforced with different fiber contents. Although composites showed interesting specific tensile properties, the estimated heat deflection temperature (HDT), that is, the maximum temperature at which a polymer system can be used as a rigid material, barely increased 4°C respect to unreinforced system. After the annealing process, the HDT of the unreinforced polymer blend increased around 25°C, whereas the composites showed an increase of at least 38°C. Nonetheless, the specific tensile strength of composite decreased approximately 48% because the adhesion between fiber and polymer matrix was damaged and cracks were formed during annealing process.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was financially supported by the Basque Country Government in the frame of Elkartek “Provimat” KK-2018/00046 and PIBA19-0044 projects

The Importance of Fiber/Matrix Adhesion and Annealing Process in Water Uptake of PLA/PMMA Matrix Composites Reinforced with Sisal Fibers: The Effect of Coupling Agent Addition

With the aim to open new applications possibilities to novel biocomposites based on PLA/PMMA matrix and reinforced with sisal fibers, it was studied the effect of water immersion aging on biocomposite tensile properties. In the current study it was evidenced the importance of the annealing process and fiber/matrix adhesion on the mechanical performance of composites after immersing in water for around 7 months. The presence of the copolymer and the annealing process led to the minor extent of damage of mechanical properties of prepared biocomposites. Results obtained in the current study suggested that although the amount of copolymer incorporated in composites was low, the presence of copolymer is crucial to improve fiber/matrix adhesion and consequently the mechanical performance of composites after immersing in water. It was observed that even though the water uptake damaged the interfacial adhesion, leading to the tensile strength reduction; however, annealed composite with 30 wt% of fiber and modified with the copolymer showed a strength value of around 53.5 MPa. It must highlighted that even though water aged for 7 months, the annealed composite with copolymer showed yet a higher strength value than dried commercial mineral-filled PP composites reported in the literature