We thank Alberta Innovates for providing the CNC and Ken Harris and Jae-Young Cho for their technical advice when preparing the CNC/agarose/D-mannitol matrix. We also thank Ben Hoffman, Heather Winchell and Nicole Diamantides for their technical advice and support with the setup and calibration of the INKREDIBLE+ 3D bioprinter.

<ol><li>Tibbitt, M. W., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hydrogels+as+extracellular+matrix+mimics+for+3D+cell+culture%5BTitle%5D)+AND+%22Biotechnology+and+Bioengineering%22%5BJournal%5D)">Hydrogels as extracellular matrix mimics for 3D cell culture.</a> Biotechnology and Bioengineering. 103 (4), 655-663 (2009).</li>
<li>Drury, J. L., Mooney, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hydrogels+for+tissue+engineering%3A+Scaffold+design+variables+and+applications%5BTitle%5D)+AND+%22Biomaterials%22%5BJournal%5D)">Hydrogels for tissue engineering: Scaffold design variables and applications.</a> Biomaterials. 24 (24), 4337-4351 (2003).</li>
<li>Lee, K. Y., Mooney, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hydrogels+for+tissue+engineering%5BTitle%5D)+AND+%22Chemical+Reviews%22%5BJournal%5D)">Hydrogels for tissue engineering.</a> Chemical Reviews. 101 (7), 1869-1879 (2001).</li>
<li>Halib, N., Ahmad, I. Nanocellulose: Insight into health and medical applications. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aHalib%2C+N+%22Handbook+of+Ecomaterials%22">Handbook of Ecomaterials</a>. , Springer. Cham. 1345-1363 (2019).</li>
<li>Alonso-Lerma, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High+performance+crystalline+nanocellulose+using+an+ancestral+endoglucanase%5BTitle%5D)+AND+%22Communications+Materials%22%5BJournal%5D)">High performance crystalline nanocellulose using an ancestral endoglucanase.</a> Communications Materials. 1 (1), 57(2020).</li>
<li>Tummala, G. K., Lopes, V. R., Mihranyan, A., Ferraz, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biocompatibility+of+nanocellulose-reinforced+PVA+hydrogel+with+human+corneal+epithelial+cells+for+ophthalmic+applications%5BTitle%5D)+AND+%22Journal+of+Functional+Biomaterials%22%5BJournal%5D)">Biocompatibility of nanocellulose-reinforced PVA hydrogel with human corneal epithelial cells for ophthalmic applications.</a> Journal of Functional Biomaterials. 10 (3), 35(2019).</li>
<li>Fey, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bacterial+nanocellulose+as+novel+carrier+for+intestinal+epithelial+cells+in+drug+delivery+studies%5BTitle%5D)+AND+%22Materials+Science+and+Engineering%3A+C%22%5BJournal%5D)">Bacterial nanocellulose as novel carrier for intestinal epithelial cells in drug delivery studies.</a> Materials Science and Engineering: C. 109, 110613(2020).</li>
<li>Ojansivu, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Wood-based+nanocellulose+and+bioactive+glass+modified+gelatin-alginate+bioinks+for+3D+bioprinting+of+bone+cells%5BTitle%5D)+AND+%22Biofabrication%22%5BJournal%5D)">Wood-based nanocellulose and bioactive glass modified gelatin-alginate bioinks for 3D bioprinting of bone cells.</a> Biofabrication. 11 (3), 035010(2019).</li>
<li>Jonsson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neuronal+networks+on+nanocellulose+scaffolds%5BTitle%5D)+AND+%22Tissue+Engineering+Part+C%3A+Methods%22%5BJournal%5D)">Neuronal networks on nanocellulose scaffolds.</a> Tissue Engineering Part C: Methods. 21 (11), 1162-1170 (2015).</li>
<li>Samulin Erdem, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cellulose+nanocrystals+modulate+alveolar+macrophage+phenotype+and+phagocytic+function%5BTitle%5D)+AND+%22Biomaterials%22%5BJournal%5D)">Cellulose nanocrystals modulate alveolar macrophage phenotype and phagocytic function.</a> Biomaterials. 203, 31-42 (2019).</li>
<li>Menas, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fibrillar+vs+crystalline+nanocellulose+pulmonary+epithelial+cell+responses%3A+Cytotoxicity+or+inflammation%5BTitle%5D)+AND+%22Chemosphere%22%5BJournal%5D)">Fibrillar vs crystalline nanocellulose pulmonary epithelial cell responses: Cytotoxicity or inflammation.</a> Chemosphere. 171, 671-680 (2017).</li>
<li>Halova, I., Draberova, L., Draber, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mast+cell+chemotaxis+chemoattractants+and+signaling+pathways%5BTitle%5D)+AND+%22Frontiers+in+Immunology%22%5BJournal%5D)">Mast cell chemotaxis chemoattractants and signaling pathways.</a> Frontiers in Immunology. 3, 1-19 (2012).</li>
<li>Groll, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+definition+of+bioinks+and+their+distinction+from+biomaterial+inks%5BTitle%5D)+AND+%22Biofabrication%22%5BJournal%5D)">A definition of bioinks and their distinction from biomaterial inks.</a> Biofabrication. 11 (1), 013001(2019).</li>
<li>Schwab, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Printability+and+shape+fidelity+of+bioinks+in+3D+bioprinting%5BTitle%5D)+AND+%22Chemical+Reviews%22%5BJournal%5D)">Printability and shape fidelity of bioinks in 3D bioprinting.</a> Chemical Reviews. 120 (19), 11028-11055 (2020).</li>
<li>Jungst, T., Smolan, W., Schacht, K., Scheibel, T., Groll, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Strategies+and+molecular+design+criteria+for+3D+printable+hydrogels%5BTitle%5D)+AND+%22Chemical+reviews%22%5BJournal%5D)">Strategies and molecular design criteria for 3D printable hydrogels.</a> Chemical reviews. 116 (3), 1496-1539 (2016).</li>
<li>Sasaki, D. T., Dumas, S. E., Engleman, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Discrimination+of+viable+and+non-viable+cells+using+propidium+iodide+in+two+color+immunofluorescence%5BTitle%5D)+AND+%22Cytometry%22%5BJournal%5D)">Discrimination of viable and non-viable cells using propidium iodide in two color immunofluorescence.</a> Cytometry. 8 (4), 413-420 (1987).</li>
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</ol>

This work was supported by the National Research Council Canada and Alberta Innovates.

The fabrication of 3D biomimetic tissues requires the successful amalgamation of the bioink, which mimics components of the extracellular matrix, with the cellular component(s) to create physiological analogs of in vivo tissues. This necessitates the use of primary cells, and not transformed cells, when fabricating physiological biomimetic tissues. Primary immunological cells, such as mast cells, however, are particularly susceptible to cytotoxic effects and phenotypic changes that may be elicited by the bioink ...

The recent interest in 3D culture systems and 3D bioprinting has focused attention on hydrogels and hydrogel composites. These composites serve as viscous yet porous biomimetics and can be composed of up to 99% water content by weight, which is comparable to biological tissues1,2,3. These features of hydrogel composites thereby permit the growth of cells without affecting their viability and function. One such composite is crystalline nanocellulose (CNC), which has been used as a reinforcing material in hydrogel composites, cell scaffolds in the development of biomaterial implants, and in two-dimensional (2D) and 3D in vitro cell culture4,5. For the most part, matrices composed of CNC are not overtly cytotoxic to human corneal epithelial cells6, intestinal epithelial cells7, human bone marrow-derived mesenchymal stem cells8, or neuron-like cells9. However, metabolic activity and proliferation of human bone marrow-derived mesenchymal stem cells decreases in correlation with the increased viscosity of wood-based nanocellulose composites, suggesting that the composition of the matrix must be carefully tested for its deleterious effects on cell functions8.
Similarly, CNC can induce inflammatory responses in macrophages upon internalization, which could have serious consequences in 3D immune cell culture systems10,11. In fact, there is very little data available on how CNC may influence other immune cell responses, particularly allergic inflammatory responses that are initiated by mast cells. Mast cells are granulated leukocytes that express the high-affinity IgE receptor, FceRI, responsible for activating inflammatory responses to allergens. Their proliferation and differentiation are dependent-upon stem cell factor (SCF), which binds the tyrosine receptor, Kit. Mast cells are derived from bone marrow progenitor cells that enter the circulation and subsequently migrate peripherally to disperse ubiquitously in all human tissues12. As mast cells function in a 3D tissue environment, they are an ideal immune cell candidate for studying immunological processes in in vitro 3D tissue models. However, to date, there is no viable in vitro 3D tissue model containing mast cells.
Due to the highly sensitive nature of mast cells and their propensity to elicit pro-inflammatory responses to external stimuli, careful consideration of the 3D matrix constituents and the bioprinting method of introducing mast cells into the 3D scaffold is required, as discussed further. Tissue constructs can be biofabricated from two broad categories of biomaterials, i.e., bioinks and biomaterial inks. The distinction lies in the fact that bioinks are cell-laden hydrogel composites, whereas biomaterial inks are hydrogel composites that are devoid of cells, as defined by Groll et al.13,14. Hence, 3D constructs printed with bioinks contain cells pre-embedded within the hydrogel matrix, whereas 3D constructs printed with biomaterial inks need to be seeded with cells post-printing. The biofabrication of culture scaffolds from hydrogel-based bioinks/biomaterial inks is most commonly performed using extrusion 3D bioprinters, which extrude the bioink/biomaterial ink through a microscale nozzle under pressure via either a pneumatically or mechanically driven piston14. Extrusion bioprinters fabricate 3D scaffolds by depositing the bioink in 2D cross-sectional patterns that are sequentially stacked upon each other in a &#39;bottom-up&#39; approach.
To be compatible with extrusion bioprinting, the hydrogel-based bioink/biomaterial ink must possess thixotropic (shear-thinning) properties, whereby the constituent hydrogel polymers of the bioink/biomaterial ink flow like a fluid through a microchannel nozzle when subjected to shear stress, but revert to a viscous, gel-like state upon removal of the shear stress15. Due to their high water content, the polymers of hydrogel-based bioinks/biomaterial inks must be crosslinked, either physically or covalently, to maintain the architecture and structural integrity of the 3D bioprinted structure. In the case of cell-laden bioinks, the cells are directly subjected to chemical stresses during the crosslinking process. The process of extruding cells encapsulated within the bioink hydrogel matrix also subjects the cells to shear stress, which can lead to reduced viability and/or cell death. Once the 3D tissue model has been bioprinted, it is difficult to discriminate between the levels of cytotoxicity elicited by the hydrogel matrix itself and the extrusion and crosslinking processes, respectively. This is particularly challenging in the context of 3D scaffolds where the cells are pre-embedded within the hydrogel matrix, thus making it difficult to remove the cells for subsequent analyses, which would be detrimental to the viability of mast cells.
A gentler approach to generating 3D tissue constructs containing mast cells involves seeding the cells into pre-printed, porous biomaterial ink 3D scaffolds from a cell culture suspension, which leverages the innate ability of mast cells to migrate from the circulation into peripheral tissues. The benefits of this cell seeding approach are two-fold: (i) the mast cells are not subjected to shear and chemical stresses from the extrusion and crosslinking processes, respectively, and (ii) the cells can be easily removed from the 3D scaffold after exposure by gentle washing for analysis without adversely affecting their viability. The additional benefit of seeding and analyzing the cell viability of mast cells on 3D bioprinted, porous hydrogel scaffolds as opposed to 2D hydrogel discs is that the 3D bioprinted hydrogel scaffolds recapitulate microscale topographical features of in vivo tissues, which are not present in bulk, 2D planar hydrogel discs. This approach is a suitable, rapid, and cost-effective approach to determine the potentially catastrophic cytotoxic effects of candidate bioink hydrogel matrices on mast cells, as well as other immunological cells, prior to investment in costly 3D tissue engineering experiments.

<table><tbody><tr><td>&lt;strong&gt;A&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Acetic Acid (glacial)</td><td>Sigma Aldrich</td><td>AX0074-6</td><td></td></tr><tr><td>Agarose (OmniPur)</td><td>EMD Millipore Corporation</td><td>2125-500GM</td><td></td></tr><tr><td>Armenian Hamster IgG Isotype Control, APC (Clone: eBio299Arm)</td><td>Thermo Fisher Scientific</td><td>17-4888-82</td><td></td></tr><tr><td>&lt;strong&gt;B&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>b-Mercaptoethanol</td><td>Fisher Scientific</td><td>O3446I-100</td><td></td></tr><tr><td>b-Nicotinamide adenine dinucleotide sodium salt (NAD)</td><td>Sigma Aldrich</td><td>N0632-5G</td><td></td></tr><tr><td>BD 5 mL Syringe (Luer-Lok Tip)</td><td>BD</td><td>309646</td><td></td></tr><tr><td>BD PrecisionGlide Needle 26G x 1/2 in</td><td>BD</td><td>305111</td><td></td></tr><tr><td>BioLite 24 Well Multidish</td><td>Thermo Fisher Scientific</td><td>930-186</td><td></td></tr><tr><td>BioLite 96 Well Multidish</td><td>Thermo Fisher Scientific</td><td>130-188</td><td></td></tr><tr><td>BioLite 175 cm&lt;sup&gt;2&lt;/sup&gt; Flask Vented</td><td>Thermo Fisher Scientific</td><td>130-191</td><td></td></tr><tr><td>Biosafety Cabinet Class II</td><td>Microzone Corp., Canada</td><td>BK-2-6-B3</td><td></td></tr><tr><td>BSA, Fraction V (OmniPur)</td><td>EMD Millipore Corporation</td><td>2930-100GM</td><td></td></tr><tr><td>&lt;strong&gt;C&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>C57BL/6 mice</td><td>The Jackson Laboratory</td><td>000664</td><td></td></tr><tr><td>CD117 (c-Kit) Monoclonal Antibody, PE (Clone: 2B8)</td><td>Thermo Fisher Scientific</td><td>12-1171-82</td><td></td></tr><tr><td>CELLINK BIOINK (3 x 3 mL Cartridge)</td><td>CELLINK LLC</td><td>IK1020000303</td><td></td></tr><tr><td>CELLINK CaCl2 Crosslinking Agent - Sterile Bottle 1 x 60 mL</td><td>CELLINK LLC</td><td>CL1010006001</td><td></td></tr><tr><td>CELLINK Empty Cartridges 3cc with End and Tip Caps</td><td>CELLINK LLC</td><td>CSC0103000102</td><td></td></tr><tr><td>CELLINK HeartWare for PC</td><td>CELLINK LLC</td><td>Version 2.4.1</td><td></td></tr><tr><td>CELLINK INKREDIBLE+ 3D BIOPRINTER</td><td>CELLINK LLC</td><td>S-10003-001</td><td></td></tr><tr><td>CELLINK Sterile Standard Conical Bioprinting Nozzles 22G</td><td>CELLINK LLC</td><td>NZ4220005001</td><td></td></tr><tr><td>CELLINK Sterile Standard Conical Bioprinting Nozzles 25G</td><td>CELLINK LLC</td><td>NZ4250005001</td><td></td></tr><tr><td>CELLINK Sterile Standard Conical Bioprinting Nozzles 27G</td><td>CELLINK LLC</td><td>NZ4270005001</td><td></td></tr><tr><td>Cell Proliferation Kit II (XTT) (Roche)</td><td>Sigma Aldrich</td><td>11465015001</td><td></td></tr><tr><td>Centrifuge (Benchtop)</td><td>Eppendorf</td><td>5804R</td><td></td></tr><tr><td>Corning Costar&amp;nbsp;96 Well Clear Flat-Bottom Non-Treated PS Microplate</td><td>Sigma Aldrich</td><td>CLS3370</td><td></td></tr><tr><td>CO2 Incubator</td><td>Binder GmbH, Germany</td><td>9040-0113</td><td></td></tr><tr><td>CytoFLEX Flow Cytometer</td><td>Beckman Coulter</td><td>A00-1-1102</td><td></td></tr><tr><td>&lt;strong&gt;D&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>D-mannitol (MilliporeSigma Calbiochem)</td><td>Fisher Scientific</td><td>44-390-7100GM</td><td></td></tr><tr><td>&lt;strong&gt;F&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Falcon 15 mL Polystyrene Conical Tubes, Sterile</td><td>Corning</td><td>352095</td><td></td></tr><tr><td>Falcon 50 mL Polystyrene Conical Tubes, Sterile</td><td>Corning</td><td>352070</td><td></td></tr><tr><td>FceR1 alpha Monoclonal Antibody, APC (Clone: MAR-1)</td><td>Thermo Fisher Scientific</td><td>17-5898-82</td><td></td></tr><tr><td>Fetal Bovine Serum (FBS), qualified, heat inactivated</td><td>Thermo Fisher Scientific</td><td>12484028</td><td></td></tr><tr><td>FlowJo Software</td><td>Becton Dickinson &amp;amp; Co. USA</td><td>Version 10.6.2</td><td></td></tr><tr><td>&lt;strong&gt;G&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>GraphPad Prism</td><td>GraphPad Software, LLC</td><td>Version 8.4.3</td><td></td></tr><tr><td>&lt;strong&gt;H&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Hemacytometer (Improved Neubauer 0.1 mmm deep levy)</td><td>VWR</td><td>15170-208</td><td></td></tr><tr><td>HEPES Sodium Salt</td><td>Fisher Scientific</td><td>BP410-500</td><td></td></tr><tr><td>&lt;strong&gt;I&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Iodonitrotetrazolium chloride (INT)</td><td>Sigma Aldrich</td><td>I10406-5G</td><td></td></tr><tr><td>&lt;strong&gt;L&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>L-Glutamine 200 mM (Gibco)</td><td>Thermo Fisher Scientific</td><td>25030-081</td><td></td></tr><tr><td>Lithium L-lactate</td><td>Sigma Aldrich</td><td>L2250-100G</td><td></td></tr><tr><td>&lt;strong&gt;M&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>MEM Non-Essential Amino Acids 100 mL 100x (Gibco)</td><td>Thermo Fisher Scientific</td><td>11140-050</td><td></td></tr><tr><td>1-Methoxy-5-methylphenazinium methyl sulfate (MPMS)</td><td>Sigma Aldrich</td><td>M8640</td><td></td></tr><tr><td>Microtubes (1.7 mL clear)</td><td>Axygen</td><td>MCT-175-C</td><td></td></tr><tr><td>Microtubes (2.0 mL clear)</td><td>Axygen</td><td>MCT-200-C</td><td></td></tr><tr><td>MilliQ Academic (for producing MilliQ ultrapure water)</td><td>Millipore</td><td>ZMQS60001</td><td></td></tr><tr><td>&lt;strong&gt;N&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Nalgene Rapid-Flow 90 mm Filter Unit (0.2 mm Pore size, 500 mL)</td><td>Thermo Fisher Scientific</td><td>566-0020</td><td></td></tr><tr><td>Nalgene Syringe filter (0.2 mm PES, 25 mm)</td><td>Thermo Fisher Scientific</td><td>725-2520</td><td></td></tr><tr><td>&lt;strong&gt;P&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Penicillin Streptomycin 100 mL (Gibco)</td><td>Thermo Fisher Scientific</td><td>15140-122</td><td></td></tr><tr><td>PBS pH 7.4, No Calcium/Magnesium, 500 mL (Gibco)&amp;nbsp;</td><td>Thermo Fisher Scientific</td><td>10010-023</td><td></td></tr><tr><td>Propidium iodide, 1.0 mg/mL (Invitrogen)&amp;nbsp;</td><td>Thermo Fisher Scientific</td><td>P3566</td><td></td></tr><tr><td>&lt;strong&gt;R&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Rat IgG2b kappa Isotype Control, PE (Clone: eB149/10H5)</td><td>Thermo Fisher Scientific</td><td>12-4031-82</td><td></td></tr><tr><td>Recombinant Murine IL-3</td><td>PeproTech, Inc.&amp;nbsp;</td><td>213-13</td><td></td></tr><tr><td>RPMI-1640 Medium 1X + 2.05 mM L-Glutamine (HyClone)</td><td>GE Healthcare</td><td>SH30027.01</td><td></td></tr><tr><td>&lt;strong&gt;S&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Sarstedt 96 well round base PS transparent micro test plate (82.1582.001)</td><td>Fisher Scientific</td><td>NC9913213</td><td></td></tr><tr><td>Sodium Azide, 500 g</td><td>Fisher Scientific</td><td>BP922I-500</td><td></td></tr><tr><td>Sodium Pyruvate (100 mM) 100X (Gibco)</td><td>Thermo Fisher Scientific</td><td>11360-070</td><td></td></tr><tr><td>&lt;strong&gt;T&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Tris Base (2-amino-2(hydroxymethyl)-1,3-propanediol)</td><td>Sigma Aldrich</td><td>252859</td><td></td></tr><tr><td>Trypan Blue solution (0.4%, for microscopy)</td><td>Sigma Aldrich</td><td>93595</td><td></td></tr><tr><td>&lt;strong&gt;V&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>VARIOSKAN LUX Microplate Spectrophotometer (Type: 3020)</td><td>Thermo Fisher Scientific</td><td>VLBL00D0</td><td></td></tr></tbody></table>

fabrication of a crystalline nanocellulose embedded agarose biomaterial ink for bone marrow-derived mast cell culture

Three-dimensional (3D) bioprinting utilizes hydrogel-based composites (or biomaterial inks) that are deposited in a pattern, forming a substrate onto which cells are deposited. Because many biomaterial inks can be potentially cytotoxic to primary cells, it is necessary to determine the biocompatibility of these hydrogel composites prior to their utilization in costly 3D tissue engineering processes. Some 3D culture methods, including bioprinting, require that cells be embedded into a 3D matrix, making it difficult to extract and analyze the cells for changes in viability and biomarker expression without eliciting mechanical damage. This protocol describes as proof of concept, a method to assess the biocompatibility of a crystalline nanocellulose (CNC) embedded agarose composite, fabricated into a 24-well culture system, with mouse bone marrow-derived mast cells (BMMCs) using flow cytometric assays for cell viability and biomarker expression.
After 18 h of exposure to the CNC/agarose/D-mannitol matrix, BMMC viability was unaltered as measured by propidium iodide (PI) permeability. However, BMMCs cultured on the CNC/agarose/D-mannitol substrate appeared to slightly increase their expression of the high-affinity IgE receptor (Fc&#949;RI) and the stem cell factor receptor (Kit; CD117), although this does not appear to be dependent on the amount of CNC in the bioink composite. The viability of BMMCs was also assessed following a time course exposure to hydrogel scaffolds that were fabricated from a commercial biomaterial ink composed of fibrillar nanocellulose (FNC) and sodium alginate using a 3D extrusion bioprinter. Over a period of 6-48 h, the FNC/alginate substrates did not adversely affect the viability of the BMMCs as determined by flow cytometry and microtiter assays (XTT and lactate dehydrogenase). This protocol describes an efficient method to rapidly screen the biochemical compatibility of candidate biomaterial inks for their utility as 3D scaffolds for post-print seeding with mast cells.

One of the most crucial characteristics of a successful biomaterial ink or culture substrate is that of biocompatibility. Primarily, the substrate must not induce cellular death. There are several microtiter-based and flow cytometric methods of quantifying cell viability and necrosis; however, these methods are not amenable to analyzing cells embedded within a hydrogel matrix. In this protocol, the above mentioned limitation is circumvented by seeding the BMMCs onto the hydrogel substrate or bioprinted scaffold. After a ...

Watch this Scientific Journal Video about Fabrication of a Crystalline Nanocellulose Embedded Agarose Biomaterial Ink for Bone Marrow-Derived Mast Cell Culture at JoVE.com

Fabrication of a Crystalline Nanocellulose Embedded Agarose Biomaterial Ink for Bone Marrow-Derived Mast Cell Culture

This protocol highlights a method to rapidly assess the biocompatibility of a crystalline nanocellulose (CNC)/agarose composite hydrogel biomaterial ink with mouse bone marrow-derived mast cells in terms of cell viability and phenotypic expression of the cell surface receptors, Kit (CD117) and high-affinity IgE receptor (Fc&#949;RI).

Three-dimensional (3D) bioprinting utilizes hydrogel-based composites (or biomaterial inks) that are deposited in a pattern, forming a substrate onto ...

fabrication-crystalline-nanocellulose-embedded-agarose-biomaterial

Research

JoVE Journal

Bioengineering

3.2K Views.  National Research Council Canada. This protocol highlights a method to rapidly assess the biocompatibility of a crystalline nanocellulose (CNC)/agarose composite hydrogel biomaterial ink with mouse bone marrow-derived mast cells in terms of cell viability and phenotypic expression of the cell surface receptors, Kit (CD117) and high-affinity IgE receptor (FcεRI).

Video: Fabrication of a Crystalline Nanocellulose Embedded Agarose Biomaterial Ink for Bone Marrow-Derived Mast Cell Culture

Fabrication of a Functionalized Magnetic Bacterial Nanocellulose with Iron Oxide Nanoparticles

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide nanoparticles (IONP) (Fe3O4) to yield a magnetic bacterial nanocellulose (MBNC). The synthesis of MBNC is a precise and specifically designed multi-step process. Briefly, bacterial nanocellulose (BNC) pellicles are formed from preserved G. xylinus strain according to our experimental requirements of size and morphology. A solution of iron(III) chloride hexahydrate (FeCl3&#183;6H2O) and iron(II) chloride tetrahydrate (FeCl2&#183;4H2O) with a 2:1 molar ratio is prepared and diluted in deoxygenated high purity water. A BNC pellicle is then introduced in the vessel with the reactants. This mixture is stirred and heated at 80 &#176;C in a silicon oil bath and ammonium hydroxide (14%) is then added by dropping to precipitate the ferrous ions into the BNC mesh. This last step allows forming in situ magnetite nanoparticles (Fe3O4) inside the bacterial nanocellulose mesh to confer magnetic properties to BNC pellicle. A toxicological assay was used to evaluate the biocompatibility of the BNC-IONP pellicle. Polyethylene glycol (PEG) was used to cover the IONPs in order to improve their biocompatibility. Scanning electron microscopy (SEM) images showed that the IONP were located preferentially in the fibril interlacing spaces of the BNC matrix, but some of them were also found along the BNC ribbons. Magnetic force microscope measurements performed on the MBNC detected the presence magnetic domains with high and weak intensity magnetic field, confirming the magnetic nature of the MBNC pellicle. Young&#39;s modulus values obtained in this work are also in a reasonable agreement with those reported for several blood vessels in previous studies.

Here, we present a protocol to make a bacterial nanocellulose (BNC) magnetic for applications in damaged blood vessel reconstruction. The BNC was synthesized by G. xylinus strain. On the other hand, magnetization of the BNC was realized through in situ precipitation of Fe2+ and Fe3+ ferrous ions inside the BNC mesh.

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide ...

Synthesis of Thermogelling Poly(N-isopropylacrylamide)-graft-chondroitin Sulfate Composites with Alginate Microparticles for Tissue Engineering

Injectable biomaterials are defined as implantable materials that can be introduced into the body as a liquid and solidify in situ. Such materials offer the clinical advantages of being implanted minimally invasively and easily forming space-filling solids in irregularly shaped defects. Injectable biomaterials have been widely investigated as scaffolds for tissue engineering. However, for the repair of certain load-bearing areas in the body, such as the intervertebral disc, scaffolds should possess adhesive properties. This will minimize the risk of dislocation during motion and ensure intimate contact with the surrounding tissue, providing adequate transmission of forces. Here, we describe the preparation and characterization of a scaffold composed of thermally sensitive poly(N-isopropylacrylamide)-graft-chondroitin sulfate (PNIPAAM-g-CS) and alginate microparticles. The PNIPAAm-g-CS copolymer forms a viscous solution in water at RT, into which alginate particles are suspended to enhance adhesion. Above the lower critical solution temperature (LCST), around 30 &#176;C, the copolymer forms a solid gel around the microparticles. We have adapted standard biomaterials characterization procedures to take into account the reversible phase transition of PNIPAAm-g-CS. Results indicate that the incorporation of 50 or 75 mg/ml&#160;alginate particles into 5% (w/v) PNIPAAm-g-CS solutions quadruple the adhesive tensile strength of PNIPAAm-gCS alone (p&#60;0.05). The incorporation of alginate microparticles also significantly increases swelling capacity of PNIPAAm-g-CS (p&#60;0.05), helping to maintain a space-filling gel within tissue defects. Finally, results of the in vitro toxicology assay kit, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and Live/Dead viability assay indicate that the adhesive is capable of supporting the survival and proliferation of encapsulated Human Embryonic Kidney (HEK) 293 cells over 5 days.

Synthesis of Thermogelling PolyN-isopropylacrylamide-graft-chondroitin Sulfate Composites with Alginate Microparticles for Tissue Engineering

An injectable tissue engineering scaffold composed of poly(N-isopropylacrylamide)-graft-chondroitin sulfate (PNIPAAm-g-CS)-containing alginate microparticles was prepared. The adhesive strength, swelling properties and in vitro biocompatibility are analyzed in this study. The characterization techniques developed here may be applicable to other thermogelling systems.

Injectable biomaterials are defined as implantable materials that can be introduced into the body as a liquid and solidify in situ. Such materials offer ...

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

The tissue-specific extracellular matrix (ECM) is a key mediator of cell function. This article describes methods for synthesizing pure ECM-derived foams and microcarriers that are stable in culture without the need for chemical crosslinking for applications in advanced 3D in vitro cell culture models or as pro-regenerative bioscaffolds.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus ...

Bioprinting of Cartilage and Skin Tissue Analogs Utilizing a Novel Passive Mixing Unit Technique for Bioink Precellularization

Bioprinting is a powerful technique for the rapid and reproducible fabrication of constructs for tissue engineering applications. In this study, both cartilage and skin analogs were fabricated after bioink pre-cellularization utilizing a novel passive mixing unit technique. This technique was developed with the aim to simplify the steps involved in the mixing of a cell suspension into a highly viscous bioink. The resolution of filaments deposited through bioprinting necessitates the assurance of uniformity in cell distribution prior to printing to avoid the deposition of regions without cells or retention of large cell clumps that can clog the needle. We demonstrate the ability to rapidly blend a cell suspension with a bioink prior to bioprinting of both cartilage and skin analogs. Both tissue analogs could be cultured for up to 4 weeks. Histological analysis demonstrated both cell viability and deposition of tissue specific extracellular matrix (ECM) markers such as glycosaminoglycans (GAGs) and collagen I respectively.

Cartilage and skin analogs were bioprinted using a nanocellulose-alginate based bioink. The bioinks were cellularized prior to printing via a single step passive mixing unit. The constructs were demonstrated to be uniformly cellularized, have high viability, and exhibit favorable markers of differentiation.

Bioprinting is a powerful technique for the rapid and reproducible fabrication of constructs for tissue engineering applications. In this study, both ...

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease modeling. Self-assembled tissues offer advantages over scaffold-based tissue engineering, such as enhanced matrix deposition, strength, and function. However, there are few available methods for fabricating 3D tissues without seeding cells on or within a supporting scaffold. Previously, we developed a system for fabricating self-assembled tissue rings by seeding cells into non-adhesive agarose wells. A polydimethylsiloxane (PDMS) negative was first cast in a machined polycarbonate mold, and then agarose was gelled in the PDMS negative to create ring-shaped cell seeding wells. However, the versatility of this approach was limited by the resolution of the tools available for machining the polycarbonate mold. Here, we demonstrate that 3D-printed plastic can be used as an alternative to machined polycarbonate for fabricating PDMS negatives. The 3D-printed mold and revised mold design is simpler to use, inexpensive to produce, and requires significantly less agarose and PDMS per cell seeding well. We have demonstrated that the resulting agarose wells can be used to create self-assembled tissue rings with customized diameters from a variety of different cell types. Rings can then be used for mechanical, functional, and histological analysis, or for fabricating larger and more complex tubular tissues.

This protocol describes a platform for fabricating self-assembled tissue rings in variable sizes using a customized 3D-printed plastic mold. PDMS negatives are cured in the 3D-printed mold; then agarose is cast in the cured PDMS negatives. Cells are seeded into the resulting agarose wells where they aggregate into tissue rings.

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease ...

3D Printed Porous Cellulose Nanocomposite Hydrogel Scaffolds

This work demonstrates the use of three-dimensional (3D) printing to produce porous cubic scaffolds using cellulose nanocomposite hydrogel ink, with controlled pore structure and mechanical properties. Cellulose nanocrystals (CNCs, 69.62 wt%) based hydrogel ink with matrix (sodium alginate and gelatin) was developed and 3D printed into scaffolds with uniform and gradient pore structure (110-1,100 &#181;m). The scaffolds showed compression modulus in the range of 0.20-0.45 MPa when tested in simulated in vivo conditions (in distilled water at 37 &#176;C). The pore sizes and the compression modulus of the 3D scaffolds matched with the requirements needed for cartilage regeneration applications. This work demonstrates that the consistency of the ink can be controlled by the concentration of the precursors and porosity can be controlled by the 3D printing process and both of these factors in return defines the mechanical properties of the 3D printed porous hydrogel scaffold. This process method can therefore be used to fabricate structurally and compositionally customized scaffolds according to the specific needs of patients.&#160;

The three critical steps of this protocol are i) developing the right composition and consistency of the cellulose hydrogel ink, ii) 3D printing of scaffolds into various pore structures with good shape fidelity and dimensions and iii) demonstration of the mechanical properties in simulated body conditions for cartilage regeneration.

This work demonstrates the use of three-dimensional (3D) printing to produce porous cubic scaffolds using cellulose nanocomposite hydrogel ink, with ...

Protocols of 3D Bioprinting of Gelatin Methacryloyl Hydrogel Based Bioinks

Gelatin methacryloyl (GelMA) has become a popular biomaterial in the field of bioprinting. The derivation of this material is gelatin, which is hydrolyzed from mammal collagen. Thus, the arginine-glycine-aspartic acid (RGD) sequences and target motifs of matrix metalloproteinase (MMP) remain on the molecular chains, which help achieve cell attachment and degradation. Furthermore, formation properties of GelMA are versatile. The methacrylamide groups allow a material to become rapidly crosslinked under light irradiation in the presence of a photoinitiator. Therefore, it makes great sense to establish suitable methods for synthesizing three-dimensional (3D) structures with this promising material. However, its low viscosity restricts GelMA's printability. Presented here are methods to carry out 3D bioprinting of GelMA hydrogels, namely the fabrication of GelMA microspheres, GelMA fibers, GelMA complex structures, and GelMA-based microfluidic chips. The resulting structures and biocompatibility of the materials as well as the printing methods are discussed. It is believed that this protocol may serve as a bridge between previously applied biomaterials and GelMA as well as contribute to the establishment of GelMA-based 3D architectures for biomedical applications.

Presented here is a method for the 3D bioprinting of gelatin methacryloyl.

Gelatin methacryloyl (GelMA) has become a popular biomaterial in the field of bioprinting. The derivation of this material is gelatin, which is hydrolyzed ...

3D Bioprinting of Murine Cortical Astrocytes for Engineering Neural-Like Tissue

Astrocytes are glial cells with an essential role in the central nervous system (CNS), including neuronal support and functionality. These cells also respond to neural injuries and act to protect the tissue from degenerative events. In vitro studies of astrocytes&#39; functionality are important to elucidate the mechanisms involved in such events and contribute to developing therapies to treat neurological disorders. This protocol describes a method to biofabricate a neural-like tissue structure rich in astrocytes by 3D bioprinting astrocytes-laden bioink. An extrusion-based 3D bioprinter was used in this work, and astrocytes were extracted from C57Bl/6 mice pups&#39; brain cortices. The bioink was prepared by mixing cortical astrocytes from up to passage 3 to a biomaterial solution composed of gelatin, gelatin-methacryloyl (GelMA), and fibrinogen, supplemented with laminin, which presented optimal bioprinting conditions. The 3D bioprinting conditions minimized cell stress, contributing to the high viability of the astrocytes during the process, in which 74.08% &#177; 1.33% of cells were viable right after bioprinting. After 1 week of incubation, the viability of astrocytes significantly increased to 83.54% &#177; 3.00%, indicating that the 3D construct represents a suitable microenvironment for cell growth. The biomaterial composition allowed cell attachment and stimulated astrocytic behavior, with cells expressing the specific astrocytes marker glial fibrillary acidic protein (GFAP) and possessing typical astrocytic morphology. This&#160;reproducible protocol provides a valuable method to biofabricate 3D neural-like tissue rich in astrocytes that resembles cells&#39; native microenvironment, useful to researchers that aim to understand astrocytes&#39; functionality and their relation to the mechanisms involved in neurological diseases.

Here we report a method of 3D bioprinting murine cortical astrocytes for biofabricating neural-like tissues to study the functionality of astrocytes in the central nervous system and the mechanisms involving glial cells in neurological diseases and treatments.

Astrocytes are glial cells with an essential role in the central nervous system (CNS), including neuronal support and functionality. These cells also ...

Ceramic Omnidirectional Bioprinting in Cell-Laden Suspensions for the Generation of Bone Analogs

Structurally, bone tissue is an inorganic-organic composite containing metabolically active cells embedded within a hierarchical, highly mineralized matrix. This organization is challenging to replicate due to the heterogeneous environment of bone. Ceramic omnidirectional bioprinting in cell-suspensions (COBICS) is a microgel-based bioprinting technique that uniquely replicates the mineral and cellular structure of bone. COBICS prints complex, biologically relevant constructs without the need for sacrificial support materials or harsh postprocessing steps (e.g., radiation and high-temperature sintering), which are two of the biggest challenges in the additive manufacturing of bone mimetic constructs. This technique is enabled via the freeform extrusion of a novel calcium phosphate-based ink within a gelatin-based microgel suspension. The yield-stress properties of the suspension allow deposition and support the printed bone structure. UV crosslinking and nanoprecipitation then "lock" it in place. The ability to print nanostructured bone-mimetic ceramics within cell-laden biomaterials provides spatiotemporal control over macro- and micro-architecture and facilitates the real-time fabrication of complex bone constructs in clinical settings.

This protocol describes a 3D printing technique to fabricate bone-like structures by depositing a calcium phosphate ink in a gelatin-based granular support. Printed bone analogs are deposited in freeform, with flexibility for direct harvesting of the print or crosslinking within a living cell matrix for multiphasic constructs.

Structurally, bone tissue is an inorganic-organic composite containing metabolically active cells embedded within a hierarchical, highly mineralized ...

Microgel-Extracellular Matrix Composite Support for the Embedded 3D Printing of Human Neural Constructs

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication of soft tissue constructs. However, granular gel formulations have been restricted to a limited number of biomaterials that allow for the cost-effective generation of large amounts of hydrogel microparticles. Therefore, granular gel support media have generally lacked the cell-adhesive and cell-instructive functions found in the native extracellular matrix (ECM).
To address this, a methodology has been developed for the generation of self-healing annealable particle-extracellular matrix (SHAPE) composites. SHAPE composites consist of a granular phase (microgels) and a continuous phase (viscous ECM solution) that, together, allow for both programmable high-fidelity printing and an adjustable biofunctional extracellular environment. This work describes how the developed methodology can be utilized for the precise biofabrication of human neural constructs.
First, alginate microparticles, which serve as the granular component in the SHAPE composites, are fabricated and combined with a collagen-based continuous component. Then, human neural stem cells are printed inside the support material, followed by the annealing of the support. The printed constructs can be maintained for weeks to allow the differentiation of the printed cells into neurons. Simultaneously, the collagen continuous phase allows for axonal outgrowth and the interconnection of regions. Finally, this works provides information on how to perform live-cell fluorescence imaging and immunocytochemistry to characterize the 3D-printed human neural constructs.

This work describes a protocol for the freeform embedded 3D printing of neural stem cells inside self-healing annealable particle-extracellular matrix composites. The protocol enables the programmable patterning of interconnected human neural tissue constructs with high fidelity.

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication ...