Name: novel process for 3d printing decellularized matrices
Uploaded: 2019-01-07T14:00:00
Description: Watch this Scientific Journal Video about Novel Process for 3D Printing Decellularized Matrices at JoVE.com

This project was partially funded by a grant from the Pediatric Orthopaedic Society of North America (POSNA) and the National Institutes of Health grant NIBIB R21EB025378-01 (Exploratory Bioengineering Research Grant).

1. Obtaining and Preprocessing Microspheres
<ol>
	<li>Produce microspheres with the desired matrix encapsulated (PLA-DM)2. 
	NOTE: It is imperative that the microspheres are of uniform size. For this reason, sieving the microspheres prior to use is essential. Although matrix decellularization and encapsulation have been detailed in previous publications2, a brief summary of the process follows.
	<ol>
		<li>First, harvest cartilage plugs from porcine hind limbs. Decel...

<ol>
	<li>Hutchmaker, D., Teoh, S., Zein, I., Ng, K. W., Schantz, J. -. T., Leahy, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+Fabrication+of+a+3D+Scaffold+for+Tissue+Engineering+Bone.">Design and Fabrication of a 3D Scaffold for Tissue Engineering Bone.</a> Synthetic Bioabsorbable Polymers and Implants. 15 (2), 845-847 (1988).</li><li>Ghosh, P., Gruber, S. M. S., Lin, C. -. Y., Whitlock, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microspheres+containing+decellularized+cartilage+induce+chondrogenesis+and+remain+functional+after+incorporation+within+a+poly(caprolactone)+filament+useful+for+fabricating+a+3D+scaffold.">Microspheres containing decellularized cartilage induce chondrogenesis and remain functional after incorporation within a poly(caprolactone) filament useful for fabricating a 3D scaffold.</a> Biofabrication. , (2018).</li><li>Partington, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+changes+caused+by+decellularization+may+compromise+mechanical+integrity+of+tracheal+scaffolds.">Biochemical changes caused by decellularization may compromise mechanical integrity of tracheal scaffolds.</a> Acta Biomaterialia. 9 (2), 5251-5261 (2013).</li><li>Hutmacher, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaffolds+in+tissue+engineering+bone+and+cartilage.">Scaffolds in tissue engineering bone and cartilage.</a> Biomaterials. 21 (24), 2529-2543 (2000).</li><li>Kang, H., Hollister, S. J., La Marca, F., Park, P., Lin, C. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+biodegradable+lumbar+interbody+fusion+cage+design+and+fabrication+using+integrated+global-local+topology+optimization+with+laser+sintering.">Porous biodegradable lumbar interbody fusion cage design and fabrication using integrated global-local topology optimization with laser sintering.</a> Journal of biomechanical engineering. 135 (10), 101013-101018 (2013).</li><li>Kang, H., Lin, C. Y., Hollister, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topology+optimization+of+three+dimensional+tissue+engineering+scaffold+architectures+for+prescribed+bulk+modulus+and+diffusivity.">Topology optimization of three dimensional tissue engineering scaffold architectures for prescribed bulk modulus and diffusivity.</a> Structural and Multidisciplinary Optimization. 42 (4), 633-644 (2010).</li><li>Lin, C. -. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+bone+engineering+using+ex+vivo.+gene+therapy+and+topology-optimized,+biodegradable+polymer+composite+scaffolds.">Functional bone engineering using ex vivo. gene therapy and topology-optimized, biodegradable polymer composite scaffolds.</a> Tissue Engineering. 11 (9-10), 1589-1598 (2005).</li><li>Lin, C. -. Y., Hsiao, C. -. C., Chen, P. -. Q., Hollister, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interbody+Fusion+Cage+Design+Using+Integrated+Global+Layout+and+Local+Microstructure+Topology+Optimization.">Interbody Fusion Cage Design Using Integrated Global Layout and Local Microstructure Topology Optimization.</a> Spine. 29 (16), 1747-1754 (2004).</li><li>Zopf, D., Hollister, S., Nelson, M., Ohye, R., Green, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioresorbable+Airway+Splint+Created+with+a+Three-Dimensional+Printer.">Bioresorbable Airway Splint Created with a Three-Dimensional Printer.</a> New England Journal of Medicine. 368 (21), 2043-2045 (2013).</li><li>Pati, F., Song, T. H., Rijal, G., Jang, J., Kim, S. W., Cho, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ornamenting+3D+printed+scaffolds+with+cell-laid+extracellular+matrix+for+bone+tissue+regeneration.">Ornamenting 3D printed scaffolds with cell-laid extracellular matrix for bone tissue regeneration.</a> Biomaterials. 37, 230-241 (2015).</li><li>Zhang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+interface+microstructure+on+interfacial+shear+strength+for+osteochondral+scaffolds+based+on+biomimetic+design+and+3D+printing.">The effect of interface microstructure on interfacial shear strength for osteochondral scaffolds based on biomimetic design and 3D printing.</a> Materials Science and Engineering C. 46, 10-15 (2015).</li><li>Williams, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=tissue+engineering+using+polycaprolactone+scaffolds+fabricated+via.+selective+laser+sintering.">tissue engineering using polycaprolactone scaffolds fabricated via. selective laser sintering.</a> Biomaterials. 26 (23), 4817-4827 (2005).</li><li>Monibi, F. A., Cook, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-Derived+Extracellular+Matrix+Bioscaffolds:+Emerging+Applications+in+Cartilage+and+Meniscus+Repair.">Tissue-Derived Extracellular Matrix Bioscaffolds: Emerging Applications in Cartilage and Meniscus Repair.</a> Tissue Engineering Part B: Reviews. , (2017).</li><li>Wiles, K., Fishman, J., Coppi, P., Birchall, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Host+Immune+Response+to+Tissue-Engineered+Organs:+Current+Problems+and+Future+Directions.">The Host Immune Response to Tissue-Engineered Organs: Current Problems and Future Directions.</a> Tissue Engineering Part B: Reviews. 22 (3), (2016).</li><li>Sutherland, A. J., Detamore, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioactive+Microsphere-Based+Scaffolds+Containing+Decellularized+Cartilage.">Bioactive Microsphere-Based Scaffolds Containing Decellularized Cartilage.</a> Macromolecular Bioscience. , (2015).</li><li>Whitlock, P. W., Smith, T. L., Poehling, G. G., Shilt, J. S., Van Dyke, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+naturally+derived,+cytocompatible,+and+architecturally+optimized+scaffold+for+tendon+and+ligament+regeneration.">A naturally derived, cytocompatible, and architecturally optimized scaffold for tendon and ligament regeneration.</a> Biomaterials. , (2007).</li><li>Whitlock, P. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+cyclic+strain+on+tensile+properties+of+a+naturally+derived,+decellularized+tendon+scaffold+seeded+with+allogeneic+tenocytes+and+associated+messenger+RNA+expression.">Effect of cyclic strain on tensile properties of a naturally derived, decellularized tendon scaffold seeded with allogeneic tenocytes and associated messenger RNA expression.</a> Journal of surgical orthopaedic advances. 22 (3), 224-232 (2013).</li><li>Whitlock, P. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+process+for+optimizing+musculoskeletal+allograft+tissue+to+improve+safety,+ultrastructural+properties,+and+cell+infiltration.">A novel process for optimizing musculoskeletal allograft tissue to improve safety, ultrastructural properties, and cell infiltration.</a> Journal of Bone and Joint Surgery - Series A. 94 (16), 1458-1467 (2012).</li><li>Schultz, G. S., Davidson, J. M., Kirsner, R. S., Herman, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+Reciprocity+in+the+Wound+Microenvironment.">Dynamic Reciprocity in the Wound Microenvironment.</a> Wound Repair Regeneration. 19 (2), 134-148 (2012).</li><li>Benders, K. E. M., van Weeren, P. R., Badylak, S. F., Saris, D. B. F., Dhert, W. J. A., Malda, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+scaffolds+for+cartilage+and+bone+regeneration.">Extracellular matrix scaffolds for cartilage and bone regeneration.</a> Trends in Biotechnology. 31 (3), 169-176 (2013).</li><li>Crapo, P., Gilbert, T., Badylak, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+overview+of+tissue+and+whole+organ+decellularization+processes.">An overview of tissue and whole organ decellularization processes.</a> Biomaterials. 32 (12), 3233-3243 (2011).</li><li>Guan, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porcine+kidneys+as+a+source+of+ECM+scaffold+for+kidney+regeneration.">Porcine kidneys as a source of ECM scaffold for kidney regeneration.</a> Materials Science and Engineering C. 56, 451-456 (2015).</li><li>Dean, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+studies+with+alkaline+phosphatase+in+the+presence+and+absence+of+inhibitors+and+divalent+cations.">Kinetic studies with alkaline phosphatase in the presence and absence of inhibitors and divalent cations.</a> Biochemistry and Molecular Biology Education. 30 (6), 401-407 (2002).</li></ol>

Both decellularized matrices and 3D printed PCL scaffolds have independently been shown to allow adhesion and proliferation of cells, validating their use for osteochondral repair10,11,12. The use of decellularized matrix in engineering approaches to tissue repair has been a subject of much interest and success in the recent past2,3,14<...

Current tissue engineering techniques for clinical applications such as bone, cartilage, tendon, and ligament reconstruction use auto- and allografts to repair damaged tissue. Each of these techniques is performed routinely as a &#34;gold standard&#34; in clinical practice by first harvesting the donor tissue either from the patient or a cadaveric match, and then placing the donor tissue into the defect site2. However, these strategies are limited by donor site morbidity, donor site scarcity for large defects, risk of infection, and difficulty finding grafts that match the desired geometry. In addition, studies have shown that allografts used for reconstruction have reduced mechanical and biologic properties when compared with native tissue3. With these considerations in mind, tissue engineers have recently turned to three dimensional (3D) bioprinting to produce custom, complex geometries that are biologically active and designed to accommodate defect size and shape while providing sufficient mechanical properties until biologic remodeling is complete.
Ideally, a 3D-printed scaffold would consist of a polymeric backbone that can retain the required mechanical stability of native tissue while the incorporated biologics offer biochemical cues to surrounding cells, leading to their migration, proliferation, differentiation, and tissue production2,5. Unfortunately, most constructs that contain biologic components are made with gels or polymers that are too weak to withstand in vivo forces experienced by the targeted tissues for auto/allograft reconstruction. Other polymers such as polylactic acid (PLA) are bioresorbable, 3D printable and structurally sound, but are printed at temperatures at or above 210 &#176;C - making it impossible for biologics to be co-printed during fabrication. Polycaprolactone (PCL) is another FDA-cleared, bioresorbable polymer that can be 3D printed at a lower temperature (65 &#176;C), which has become increasingly popular in fabricating patient-specific implants with complex morphologies5,6,7,8,9. However, most bioprinters using pneumatic technology make it impossible to print PCL at lower temperatures where biological activities can remain unharmed. To date, the integration of these polymers with auto/allografts into a novel printable biomaterial has yet to be accomplished. In the absence of such a material, a true tissue engineered approach to tissue reconstruction is unlikely. Therefore, we have sought to combine PLA, PCL, and decellularized allograft matrices (DM) to utilize the advantages of each material in order to manufacture a viable construct capable of reconstructing complex tissues. This process would provide the initial mechanical strength necessary to resist in vivo forces and the thermal stability to accommodate additive manufacturing in a construct that induces formation of the desired tissue.
In a recent attempt to address the aforementioned hurdles, we showed that it is feasible to encapsulate decellularized cartilage extracellular matrix within a thermally protective PLA barrier that can be extruded within PCL filaments, maintaining the ability of DM to influence surrounding host cells2. This has inspired us to seek clinically effective approaches for tissue reconstruction. In the current study, we utilize the platform technology to build all-in-one scaffolds that include PLA, DM, and PCL (PLA-DM/PCL).
Our goal is to improve the efficacy and utility of allografts using the proposed novel biofabrication technique to more accurately recapitulate native tissue, to ultimately use them in various applications.

<table border="0" cellpadding="0" cellspacing="0" style="width:877px;" width="877">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Sieve machine</td>
			<td style="width:396px;">Haver &#38; Boecker Tyler</td>
			<td style="width:132px;">Ro-Tap RX 29-E Pure</td>
			<td style="width:155px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 90 um</td>
			<td>Fisherbrand</td>
			<td>170328156</td>
			<td>No. 170</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 53 um</td>
			<td>Fisherbrand</td>
			<td>162513588</td>
			<td>No. 270</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sieve 106 um</td>
			<td>Fisherbrand</td>
			<td>162018121</td>
			<td>No. 140</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sputter coater</td>
			<td>Leica</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scanning Electron Microscope</td>
			<td>Hitachi, USA</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filabot EX2</td>
			<td>Filabot.com</td>
			<td>FB00061</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filabot Spooler</td>
			<td>Filabot.com</td>
			<td>FB00073</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CAPA 6506</td>
			<td>Perstorp</td>
			<td>24980-41-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phosphate buffered saline, PBS</td>
			<td>Gibco</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">6&#34; Fan</td>
			<td>Comfort Zone, Amazon</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultrasonic Water Bath</td>
			<td>Cole Parmer</td>
			<td>SK-08895-13</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dreamer</td>
			<td>FlashForge</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Drum Mixer</td>
			<td>Custom made</td>
			<td>n/a</td>
			<td>Similar piece of equipment: https://www.coleparmer.com/i/argos-technologies-flexiroll-digital-tube-roller-shaker-120-vac/0439744?PubID=UX&#38;persist=true&#38;ip= 
			no&#38;gclid=CjwKCAjw- 
			dXaBRAEEiwAbwCi5khGDMz0 
			dTjsraEsBGfhMEH7ytx 
			LQWGUPNgUJYQ1p3vj_yxkYoI_ 
			ixoC9GwQAvD_BwE</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Micro Balance</td>
			<td>Mettler Toledo, Fisher Scientific</td>
			<td>01-913-851</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Simplify3D</td>
			<td>Simplify3D</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SolidWorks</td>
			<td>SolidWorks</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microspheres</td>
			<td>Produced in-house, see concurrently submitted JoVE submission</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">p-nitrophenyl phosphate, disodium salt, hexahydrate</td>
			<td>Millipore</td>
			<td>4876-5GM</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phosphatase, alkaline</td>
			<td>Roche Diagnostics GmbH</td>
			<td>10 713 023 001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Absorbance Reader</td>
			<td>Tecan</td>
			<td>Sunrise</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tris-HCl Buffer</td>
			<td>Sigma-Aldrich</td>
			<td>T6455-100ML</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Heated shaker</td>
			<td>New Brunswick Scientific</td>
			<td>Excella E24</td>
			<td></td>
		</tr>
	</tbody>
</table>

novel process for 3d printing decellularized matrices

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can provide mechanical stability similar to native tissue while biologic agents offer compositional cues to progenitor cells, leading to their migration, proliferation, and differentiation to reconstitute the original tissues/organs1,2. Unfortunately, many 3D printing compatible, bioresorbable polymers (such as polylactic acid, PLA) are printed at temperatures of 210 &#176;C or higher - temperatures that are detrimental to biologics. On the other hand, polycaprolactone (PCL), a different type of polyester, is a bioresorbable, 3D printable material that has a gentler printing temperature of 65 &#176;C. Therefore, it was hypothesized that decellularized extracellular matrix (DM) contained within a thermally protective PLA barrier could be printed within PCL filament and remain in its functional conformation. In this work, osteochondral repair was the application for which the hypothesis was tested. As such, porcine cartilage was decellularized and encapsulated in polylactic acid (PLA) microspheres which were then extruded with polycaprolactone (PCL) into filament to produce 3D constructs via fused deposition modeling. The constructs with or without the microspheres (PLA-DM/PCL and PCL(-), respectively) were evaluated for differences in surface features.

After sieving, microspheres should appear uniform and be free from aggregates. Under SEM, the sieved microspheres may have small pores on their surface, but will otherwise be spherical and smooth, as shown in Figure 1. All extruded filaments should be of uniform diameter and circular cross-section. A filament that contains microspheres (PLA-DM/PCL) will have a slightly more matte finish while a PCL-only (PCL(-)) filament would look more glossy. The PLA-DM/PCL...

Watch this Scientific Journal Video about Novel Process for 3D Printing Decellularized Matrices at JoVE.com

Novel Process for 3D Printing Decellularized Matrices

This protocol describes the production of polycaprolactone (PCL) filament with embedded polylactic acid (PLA) microspheres which contain decellularized matrices (DM) for 3D printing of structural tissue engineering constructs.

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can ...

This method allows co-printing of both structural synthetics and biologic components for tissue-engineered scaffolds. These scaffolds can replicate the native tissue environment more accurately, which can be beneficial for cultured cells. The main advantage of this technique is that it can print mechanically sound structures without damaging the biologic material encapsulated within the scaffolds in an all-in-one technique for tissue engineering.Produce microspheres with the desired matrix encapsulated. These microspheres were made with decellularized cartilage from porcine hind limbs. They vary in size.Work with a sieve machine to obtain microspheres of uniformed size. Ensure the three sieve trays have been thoroughly cleaned and dried prior to use. Assemble the sieve shaker with the larger mesh tray on top and the smaller mesh tray in the middle.Put the sieve pan on the bottom. Place dry microspheres in the top-most tray. Then place the lid on the tray.Coarse sieve for eight to ten minutes. Then fine sieve for eight to ten minutes. While waiting, arrange weigh paper for the sieved spheres.When sieving is complete, carefully remove a sieve tray. Place the tray upside down on the weigh paper. Gently tap the sides to ensure most of the spheres fall out.With all of the sieve plates emptied onto weigh paper, discard the oversized and undersized spheres. The remaining spheres have the correct size for use in subsequent steps. Place these spheres into a labeled centrifuge tube.Store the tube in a 20 degree Celsius freezer until needed. Weigh the material necessary to make the filament material. Make a one-to-four weight ratio of microspheres to polycaprolactone powder with at least 25 grams of microspheres.Transfer the powder mixture to a miniature rolling mixer. Mix the powder at 20 rotations per minute for five minutes. After five minutes, stop the rotation and flip the container.Then mix at 20 rpm for an additional five minutes. To continue, take the mixture to an extruder and spooler setup. Setup the extruder so its outlet is about 60 centimeters from the inlet of a spooler.Then at the extruder heating element, be sure there is no insulating jacket. Place a desktop fan about halfway between the extruder and spooler to cool the extrudate. Put another fan near the heating jacket to cool it with ambient air.Next ensure the proper nozzle is attached to the extruder and set the heating element temperature. Start the cooling fans and allow the instrument to reach a steady state. After 20 to 30 minutes, get the microsphere PCL mixture and fill the extruder hopper.Turn on the spooler and the extruder auger to initiate filament extrusion. Use forceps and manually pull the initial extruded filament. Feed the filament to the filament spooler.As it is extruded, observe the filament to identify its composition. After some time, the filament composition will appear uniform which is desired. Wrap tape around the filament to mark the start of the uniform region.Beyond the spooler rollers, monitor the diameter of the filament. Use calipers to test if the diameter is close to the desired 1.75 mm. Adjust the spooler and extruder speeds and temperatures as necessary.To adjust adjust the filament diameter, first alter the spooler and extruder speeds. You may also change the extruder temperature, although this is usually not necessary. Continue refilling the hopper and extruding until all of powder is used.When the hopper is almost empty, add PCL powder to the hopper to flush out the microsphere mixture. Monitor the extrudate while adding the PCL powder. At first, microspheres will still be visible in the extrudate.Eventually when no more microspheres are visible, stop adding the PCL. Separate and label the filament with microspheres in the desired concentration. When there is minimal powder in the hopper, stop extruding and turn off the equipment.The filament can be used in a standard fused deposition modeling printer. Load the filament into the printer that is fitted with nozzles of the desired diameter. With the model loaded, set the temperature and linear speed for the printing and begin depositing the filament.The custom filament is deposited layer by layer. Pay special attention to the first layer and adjust settings as needed. These two 3D printed scaffolds are difficult to distinguish at this scale.One has filament containing polycapralactone, PCL only. The other has PCL filament with embedded microspheres of polylactic acid and decelluarized matrices. Viewed using scanning electron microscopy, the PCL-only scaffold appears mostly smooth.By contrast, for the other filament, microspheres embedded in the PCL are visible throughout the sample. While attempting this procedure, it is important to remember that over or undersized microspheres can impact the flow dynamics of the material in the extruder. For this reason, be sure to properly prepare your microspheres prior to use.In order to minimize waste, it is advisable to create one large batch of filament required for all experiments rather than to create smaller batches more frequently. Expertise in filament production will come over time. Scaffolds produced following this procedure can be further assessed in vitro and in vivo to answer additional questions about enhanced induction and mechanical strength compared to other bio-printed scaffolds.After its development, this technique paved the way for researchers in the field of tissue engineering to explore contragenic induction of decelluarized porcine matrix within the 3D scaffolds. Don't forget that working with small particulates can present respiratory hazards. Wearing a small particulate mask during this procedure is encouraged.

novel-process-for-3d-printing-decellularized-matrices

Research

JoVE Journal

Bioengineering

Preparation of Complaint Matrices for Quantifying Cellular Contraction

The regulation of cellular adhesion to the extracellular matrix (ECM) is essential for cell migration and ECM remodeling. Focal adhesions are macromolecular assemblies that couple the contractile F-actin cytoskeleton to the ECM. This connection allows for the transmission of intracellular mechanical forces across the cell membrane to the underlying substrate. Recent work has shown the mechanical properties of the ECM regulate focal adhesion and F-actin morphology as well as numerous physiological processes, including cell differentiation, division, proliferation and migration. Thus, the use of cell culture substrates has become an increasingly prevalent method to precisely control and modulate ECM mechanical properties.
To quantify traction forces at focal adhesions in an adherent cell, compliant substrates are used in conjunction with high-resolution imaging and computational techniques in a method termed traction force microscopy (TFM). This technique relies on measurements of the local magnitude and direction of substrate deformations induced by cellular contraction. In combination with high-resolution fluorescence microscopy of fluorescently tagged proteins, it is possible to correlate cytoskeletal organization and remodeling with traction forces.
Here we present a detailed experimental protocol for the preparation of two-dimensional, compliant matrices for the purpose of creating a cell culture substrate with a well-characterized, tunable mechanical stiffness, which is suitable for measuring cellular contraction. These protocols include the fabrication of polyacrylamide hydrogels, coating of ECM proteins on such gels, plating cells on gels, and high-resolution confocal microscopy using a perfusion chamber. Additionally, we provide a representative sample of data demonstrating location and magnitude of cellular forces using cited TFM protocols.

In this video, we demonstrate the experimental techniques used to fabricate compliant, extracellular matrix (ECM) coated substrates suitable for cell culture, and which are amenable to traction force microscopy and observing effects of ECM stiffness on cell behavior.

The regulation of cellular adhesion to the extracellular matrix (ECM) is essential for cell migration and ECM remodeling.  Focal adhesions are ...

Neonatal Cardiac Scaffolds: Novel Matrices for Regenerative Studies

The only definitive therapy for end stage heart failure is orthotopic heart transplantation. Each year, it is estimated that more than 100,000 donor hearts are needed for cardiac transplantation procedures in the United States1-2. Due to the limited numbers of donors, only approximately 2,400 transplants are performed each year in the U.S.2. Numerous approaches, from cell therapy studies to implantation of mechanical assist devices, have been undertaken, either alone or in combination, in an attempt to coax the heart to repair itself or to rest the failing heart3. In spite of these efforts, ventricular assist devices are still largely used for the purpose of bridging to transplantation and the utility of cell therapies, while they hold some curative promise, is still limited to clinical trials. Additionally, direct xenotransplantation has been attempted but success has been limited due to immune rejection. Clearly, another strategy is required to produce additional organs for transplantation and, ideally, these organs would be autologous so as to avoid the complications associated with rejection and lifetime immunosuppression. Decellularization is a process of removing resident cells from tissues to expose the native extracellular matrix (ECM) or scaffold. Perfusion decellularization offers complete preservation of the three dimensional structure of the tissue, while leaving the bulk of the mechanical properties of the tissue intact4. These scaffolds can be utilized for repopulation with healthy cells to generate research models and, possibly, much needed organs for transplantation. We have exposed the scaffolds from neonatal mice (P3), known to retain remarkable cardiac regenerative capabilities,5-8 to detergent mediated decellularization and we repopulated these scaffolds with murine cardiac cells. These studies support the feasibility of engineering a neonatal heart construct. They further allow for the investigation as to whether the ECM of early postnatal hearts may harbor cues that will result in improved recellularization strategies.

In these studies, we provide methodology for novel, neonatal, murine cardiac scaffolds for use in regenerative studies.

The only definitive therapy for end stage heart failure is orthotopic heart transplantation.  Each year, it is estimated that more than 100,000 donor ...

2D and 3D Matrices to Study Linear Invadosome Formation and Activity

Cell adhesion, migration, and invasion are involved in many physiological and pathological processes. For example, during metastasis formation, tumor cells have to cross anatomical barriers to invade and migrate through the surrounding tissue in order to reach blood or lymphatic vessels. This requires the interaction between cells and the extracellular matrix (ECM). At the cellular level, many cells, including the majority of cancer cells, are able to form invadosomes, which are F-actin-based structures capable of degrading ECM. Invadosomes are protrusive actin structures that recruit and activate matrix metalloproteinases (MMPs). The molecular composition, density, organization, and stiffness of the ECM are crucial in regulating invadosome formation and activation. In vitro, a gelatin assay is the standard assay used to observe and quantify invadosome degradation activity. However, gelatin, which is denatured collagen I, is not a physiological matrix element. A novel assay using type I collagen fibrils was developed and used to demonstrate that this physiological matrix is a potent inducer of invadosomes. Invadosomes that form along the collagen fibrils are known as linear invadosomes due to their linear organization on the fibers. Moreover, molecular analysis of linear invadosomes showed that the discoidin domain receptor 1 (DDR1) is the receptor involved in their formation. These data clearly demonstrate the importance of using a physiologically relevant matrix in order to understand the complex interactions between cells and the ECM.

This protocol describes how to prepare a 2D mixed matrix, consisting of gelatin and collagen I, and a 3D collagen I plug to study linear invadosomes. These protocols allow for the study of linear invadosome formation, matrix degradation activity, and the invasion capabilities of primary cells and cancer cell lines.

Cell adhesion, migration, and invasion are involved in many physiological and pathological processes. For example, during metastasis formation, tumor ...

Mammalian Cell Division in 3D Matrices via Quantitative Confocal Reflection Microscopy

The study of how mammalian cell division is regulated in a 3D environment remains largely unexplored despite its physiological relevance and therapeutic significance. Possible reasons for the lack of exploration are the experimental limitations and technical challenges that render the study of cell division in 3D culture inefficient. Here, we describe an imaging-based method to efficiently study mammalian cell division and cell-matrix interactions in 3D collagen matrices. Cells labeled with fluorescent H2B are synchronized using the combination of thymidine blocking and nocodazole treatment, followed by a mechanical shake-off technique. Synchronized cells are then embedded into a 3D collagen matrix. Cell division is monitored using live-cell microscopy. The deformation of collagen fibers during and after cell division, which is an indicator of cell-matrix interaction, can be monitored and quantified using quantitative confocal reflection microscopy. The method provides an efficient and general approach to study mammalian cell division and cell-matrix interactions in a physiologically relevant 3D environment. This approach not only provides novel insights into the molecular basis of the development of normal tissue and diseases, but also allows for the design of novel diagnostic and therapeutic approaches.

This protocol efficiently studies mammalian cell division in 3D collagen matrices by integrating synchronization of cell division, monitoring of division events in 3D matrices using live-cell imaging technique, time-resolved confocal reflection microscopy and quantitative imaging analysis.

The study of how mammalian cell division is regulated in a 3D environment remains largely unexplored despite its physiological relevance and therapeutic ...

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 ...

Pancreatic Tissue-Derived Extracellular Matrix Bioink for Printing 3D Cell-Laden Pancreatic Tissue Constructs

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary complications. However, islet transplantation still has several limitations such as the low viability of transplanted islets due to poor islet engraftment and hostile environments. In addition, the insulin-producing cells differentiated from human pluripotent stem cells have limited ability to secrete sufficient hormones that can regulate the blood glucose level; therefore, improving the maturation by culturing cells with proper microenvironmental cues is strongly required. In this article, we elucidate protocols for preparing a pancreatic tissue-derived decellularized extracellular matrix (pdECM) bioink to provide a beneficial microenvironment that can increase glucose sensitivity of pancreatic islets, followed by describing the processes for generating 3D pancreatic tissue constructs using a microextrusion-based bioprinting technique.

Decellularized extracellular matrix (dECM) can provide suitable microenvironmental cues to recapitulate the inherent functions of target tissues in an engineered construct. This article elucidates the protocols for the decellularization of pancreatic tissue, evaluation of pancreatic tissue-derived dECM bioink, and generation of 3D pancreatic tissue constructs using a bioprinting technique.

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary ...

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 Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell cultures. Microcarrier culture technology has become one of the main techniques in cytological research and is commonly used in the field of large-scale cell expansion. Microcarriers have also been shown to play an increasingly important role in in vitro tissue engineering construction and clinical drug screening. Current methods for preparing microcarriers include microfluidic chips and inkjet printing, which often rely on complex flow channel design, an incompatible two-phase interface, and a fixed nozzle shape. These methods face the challenges of complex nozzle processing, inconvenient nozzle changes, and excessive extrusion forces when applied to multiple bioink. In this study, a 3D printing technique, called alternating viscous-inertial force jetting, was applied to enable the construction of hydrogel microcarriers with a diameter of 100-300 &#181;m. Cells were subsequently seeded on microcarriers to form tissue engineering modules. Compared to existing methods, this method offers a free nozzle tip diameter, flexible nozzle switching, free control of printing parameters, and mild printing conditions for a wide range of bioactive materials.

3D Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Presented here is a mild 3D printing technique driven by alternating viscous-inertial forces to enable the construction of hydrogel microcarriers. Homemade nozzles offer flexibility, allowing easy replacement for different materials and diameters. Cell binding microcarriers with a diameter of 50-500 &#181;m can be obtained and collected for further culturing.

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell ...

Fabrication of Engineered Vascular Flaps Using 3D Printing Technologies

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create tissues by adding layer upon layer of printable biomaterials, termed bioinks, and cells in an orderly and automatic manner, which allows for creating highly intricate structures that traditional tissue engineering techniques cannot achieve. Thus, 3D bioprinting is an appealing in vitro approach to mimic the native vasculature complex structure, ranging from millimetric vessels to microvascular networks. 
Advances in 3D bioprinting in granular hydrogels enabled the high-resolution extrusion of low-viscosity extracellular matrix-based bioinks. This work presents a combined 3D bioprinting and sacrificial mold-based 3D printing approach for fabricating engineered vascularized tissue flaps. 3D bioprinting of endothelial and support cells using recombinant collagen-methacrylate bioink within a gelatin support bath is utilized for the fabrication of a self-assembled capillary network. This printed microvasculature is assembled around a mesoscale vessel-like porous scaffold, fabricated using a sacrificial 3D printed mold, and is seeded with endothelial cells. 
This assembly induces the endothelium of the mesoscale vessel to anastomose with the surrounding capillary network, establishing a hierarchical vascular network within an engineered tissue flap. The engineered flap is then directly implanted by surgical anastomosis to a rat femoral artery using a cuff technique. The described methods can be expanded for the fabrication of various vascularized tissue flaps for use in reconstruction surgery and vascularization studies.

Engineered flaps require an incorporated functional vascular network. In this protocol, we present a method of fabricating a 3D printed tissue flap containing a hierarchical vascular network and its direct microsurgical anastomoses to rat femoral artery.

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create ...

Low-Dose Gamma Radiation Sterilization for Decellularized Tracheal Grafts

One of the main key aspects in ensuring that a transplant evolves correctly is the sterility of the medium. Decellularized tracheal transplantation involves implanting an organ that was originally in contact with the environment, thus not being sterile from the outset. While the decellularization protocol (through detergent exposition [2% sodium dodecyl sulfate], continuous stirring, and osmotic shocks) is conducted in line with aseptic measures, it does not provide sterilization. Therefore, one of the main challenges is ensuring sterility prior to in vivo implantation. Although there are established gamma radiation sterilization protocols for inorganic materials, there are no such measures for organic materials. Additionally, the protocols in place for inorganic materials cannot be applied to organic materials, as the established radiation dose (25 kGy) would completely destroy the implant. This paper studies the effect of an escalated radiation dose in a decellularized rabbit trachea. We maintained the dose range (kGy) and tested escalated doses until finding the minimal dose at which sterilization is achieved. After determining the dose, we studied effects of it on the organ, both histologically and biomechanically. We determined that while 0.5 kGy did not achieve sterility, doses of both 1 kGy and 2 kGy did, with 1 kGy, therefore, being the minimal dose necessary to achieve sterilization. Microscopic studies showed no relevant changes compared to non-sterilized organs. Axial biomechanical characteristics were not altered at all, and only a slight reduction in the force per unit of length that the organ can radially tolerate was observed. We can therefore conclude that 1 kGy achieves complete sterilization of decellularized rabbit trachea with a minimal, if any, effects on the organ.

Obtaining sterilization is essential for tracheal tissue transplant. Herein, we present a sterilization protocol using low-dose gamma irradiation that is fully tolerated by organs.

One of the main key aspects in ensuring that a transplant evolves correctly is the sterility of the medium. Decellularized tracheal transplantation ...