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Abstract Among various available 3D bioprinting techniques, extrusion-based three-dimensional (3D) bio-printing allows the deposition of cell-laden bio-ink, ensuring predefined scaffold architecture that may offer living tissue regeneration. With a combination of unique characteristics such as biocompatibility, less cell toxicity, and high-water content, natural hydrogels are a great candidate for bio-ink formulation for the extrusion-based 3D bioprinting process. However, due to its low mechanical integrity, hydrogel faces a common challenge in maintaining structural ty. To tackle this challenge, we characterized the rheological properties of a set of hybrid hydrogels composed of cellulose-derived nanofiber (TEMPO-mediated nano-fibrillated cellulose, TONFC), carboxymethyl cellulose (CMC) and commonly used alginate. A total of 46 compositions were prepared using higher (0.5% and 1.0%) and lower percentages (0.005% and 0.01%) of TONFC, 1%–4% of CMC, and 1%–4% of alginate to analyze the rheological properties. The shear thinning coefficients of n and K were determined for each composition from the flow diagram and co-related with the 3D printability. The ability to control rheological properties with various ratios of a nanofiber can help achieve a 3D bio-printed scaffold with defined scaffold architecture. 

Abstract Three-dimensional (3D) bioprinting is a promising technique for creating patient-specific 3D scaffolds of tissues or organs. An appropriate culturing process is critical to confirm encapsulated and seeded cells’ excellent viability and proliferation into scaffolds materials. Traditional stagnant cell culturing methods don’t ensure entering medium inside areas or passing through the scaffolds. To resolve this issue, we developed a customized perfusion bioreactor to supply the growth medium dynamically to the encapsulated or seeded cells. Our custom-designed bioreactor improves the in vivo stimuli and conditions, which may enhance cell viability and proliferation performance. A design of a dual medium tank was utilized allowing the replacement of already-used medium without interrupting perfusion. Accommodating an array of cassettes in a newly designed perfusion chamber allowed a wide range of scaffolds with various size and shapers to hold. In this paper, we explored fluid flow response on scaffolds fabricated with various material compositions with different viscosities. We fabricated scaffolds following a 00–900 deposition pattern with 8% Alginate, 4% Alginate-4% Carboxymethyl Cellulose (CMC), and 2% Alginate-6% CMC incubated, allowing a constant fluid flow for various periods such as 1, 2, 4, and 8 hours. The change of scaffolds fabricated with multiple material compositions was determined in terms of swelling rate, i.e., change of filament width, and material diffusion, i.e., comparison of dry material weight before and after incubation. This comparative study can assist in application-based materials selection suitable for incubating in a perfusion bioreactor. 

Abstract Due to the three-dimensional nature of the 3D bio-printed scaffolds, typical stagnant cell culturing methods don’t ensure entering medium inside areas or passing through the scaffolds. The bioreactor has frequently provided the required growth medium to encapsulated- and seeded-cells in 3D bio-printed scaffolds. To address this issue, we developed a customized perfusion bioreactor to supply the growth medium dynamically to the cells encapsulated or seeded in the scaffolds. The dynamic supply of fresh growth medium may help improve cell viability and proliferation. Because of its uniform nutrition distribution and flow-induced shear stress within the tissue-engineering scaffold, perfusion bioreactors have been used in a variety of tissue engineering applications. Including a modified setup of our designed bioreactor may improve the in vivo stimuli and conditions, eventually enhancing the overall performance of tissue regeneration. In this paper, we explored the response of fluid flow to certain types of scaffold pore geometries and porosities. We used a simulation technique to determine fluid flow turbulence through various pore geometries such as uniform triangular, square, diamond, circular, and honeycomb. We used variable pore sizes of the scaffold maintaining constant porosity to analyze the fluid flow. Based on the results, optimum designs for scaffolds were determined. 

Abstract Three-dimensional (3D) bio-printing is a rapidly growing field attempting to recreate functional tissues for medical and pharmaceutical purposes. The printability of multiple materials encapsulating various living cells can take this emerging effort closer to tissue regeneration. In our earlier research, we designed a Y-like nozzle connector system capable of switching materials between more than one filament with continuous deposition. The device had a fixed switching angle, was made from plastic, and was suitable for one-time use. This paper presents the extension of our previously proposed nozzle system. We considered 30°, 45°, 60°, and 90° angles (vertical and tilted) between the two materials and chose stainless steel as a material to fabricate those nozzle connectors. The overall material switching time was recorded and compared to analyze the effects of those various angles. Our previously developed hybrid hydrogel (4% Alginate and 4% Carboxymethyl Cellulose, CMC) was used as a test material to flow through the nozzle system. These in-house fabricated nozzle connectors are reusable, easy to clean, and sterile, allowing smooth material transition and flow. 

Among various available 3D bioprinting techniques, extrusion-based three-dimensional (3D) bioprinting allows the deposition of cell-laden bioink, ensuring predefined scaffold architecture that may offer living tissue regeneration. With a combination of unique characteristics such as biocompatibility, less cell toxicity, and high water content, natural hydrogels are a great candidate for bioink formulation for the extrusion-based 3D bioprinting process. However, due to its low mechanical integrity, hydrogel faces a common challenge in maintaining structural integrity. To tackle this challenge, the rheological properties, specifically the shear thinning behavior (reduction of viscosity with increasing the applied load/shear rate on hydrogels) of a set of hybrid hydrogels composed of cellulose-derived nanofiber (TEMPO-mediated nano-fibrillated cellulose, TO-NFC), carboxymethyl cellulose (CMC), and commonly used alginate, were explored. A total of 46 compositions were prepared using higher (0.5% and 1.0%) and lower percentages (0.005% and 0.01%) of TO-NFC, 1–4% of CMC, and 1–4% of alginate to analyze the shear thinning factors such as the values of n and K, which were determined for each composition from the flow diagram and co-related with the 3D printability. The ability to tune shear thinning factors with various ratios of a nanofiber can help achieve a 3D bio-printed scaffold with defined scaffold architecture.